course pack soil laboratory experiment
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Soil Mechanics Laboratory
Course Documents
California State Universit , Fullerton
Civil & Environmental Engineering Department
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Table of Contents
Page No.
1. Syllabus 1
2. Sieve Analysis 6
3. Hydrometer Analysis 10
4. Specific Gravity Test 14
5. Liquid Limit Test 16
6. Plastic Limit Test 20
7. Classification of Soil 22
8. Compaction Test 28
9. Laboratory Compaction Test 35
10. Constant Head and Falling Head Permeability Test 46
11. Calculation of Seepage Discharge and Seepage Pressure 54
12. Verification of Seepage Through Cofferdam 65
13. Measurement of Shear Strength of Soil with Direct Shear Test 68
14. Measurement of Shear Strength of Soil with Triaxial Test 72
15. UU Triaxial Test 81
16. Slope Stability Analysis 92
17. How Much Did You Learn? 102
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California State University, FullertonCollege of Engineering and Computer Science
Civil and Environmental Engineering Department
EGCE 324L SOIL MECHANICS LABORATORYSCH 22037
Spring Semester 2013
Instructor: Santiago Caballero M.C.E.Office: E 308Fax: (657) 278-3916Email: sacaballero@fullerton.edu
Class Meeting: T 13:00 – 15:45Class Room: EC-063Units: 1
Prerequisite EGCE 324 and ENGL 101Students registered for this course should have completed the prerequisite courses. During thesemester, the department will verify the prerequisite requirements. If any student has completedthe prerequisite course at another school, please submit appropriate documents to thedepartment secretary. Otherwise, their name will be deleted from the class list at any time duringthe semester.
Text Book
Soil Mechanics Laboratory Manual (with disk) by Braja M. Das, 7th Edition, 2009, Oxford
University Press , ISBN 9780195367591
Reference Materials
· Handouts, website URLs, visuals, and other materials will be provided during class orposted on Blackboard.
· Principle of geotechnical Engineering by Braja M. Das, 7th
Edition, Cengage Learning(2010).
· Engineering Properties of Soils and Their Measurements by Joseph E. Bowles, 4th
Edition, McGraw-Hill (1992).
· Soil Mechanics Lab Manual by Michael Kalinski, John Wiley (2006)
· Annual Book of American Society for Testing and Materials (ASTM) Standards.
Office HoursTuesday 10:00 – 11:00
Course DescriptionBehavior and properties of soils, Application to foundation and slope design, liquefaction, andseepage.
Course Learning ObjectivesThis course will provide the students with sufficient guidance and resources to learn theproperties and behavior of soils in accordance with the principle of soil mechanics, theexperimental method of testing as well as data interpretation and presentation, and theapplication of soil test data for the design of engineering structures. Upon completion of thiscourse the students will be able to:
Ø Acquire basic knowledge about the properties and behavior of soils in accordance withthe principles of soil mechanics and foundation engineering.
Ø Use experimental methods and testing equipments related to earth, earth supported, andearth retaining structures and foundations.
Ø Utilize test data to determine engineering properties of soils to solve basic engineeringdesign problems in geotechnical field.
Ø Prepare reports based on test results following evaluations.
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Topics CoveredParticle Size AnalysisSpecific GravityPlasticity LimitsSoil Classification for Engineering PurposesPermeabilitySeepage AnalysisSoil CompactionConsolidationDirect Shear TestUnconfined Compression TestTriaxial Shear TestSlope Stability Analysis and Design
Program Educational Objectives
The educational objectives of the program are as follows:
· Technical Growth: Graduates will be successful in modern engineering practice, integrate
into the local and global workforce, and contribute to the economy of California and the
nation.
Assessment of Student’s LearningThe effect of this course on student’s learning ability will be assessed according to the followingcriteria:
Ø An ability to apply knowledge of mathematics, science, and engineering.Ø An ability to design and conduct experiments as well as to analyze and interpret data.Ø An ability to communicate effectively.Ø An ability to use the techniques, skills, and modern engineering tools necessary for
engineering practice.
Laboratory Reports and Other Assignments
· This course is incorporated in one of the upper-division writing courses requirements. Gradeof ‘C’ or above is required to satisfy the upper-division writing requirement.
· Students are required to submit a report of the lab works conducted in each week. Report isdue at the beginning of the class in the following week. There will be no credit for the latesubmission, unless accompanied with a university approved excuse. Lab reports should beprepared according to the report format and guideline provided by the instructor. Quality ofpresentation, technical writing quality, summary and conclusion, and technical informationpresented in the report are the major factors for the evaluation of the report. Writing andsketches should be neat. Students are required to make a PowerPoint presentation of one ofthe assigned projects in a group. Members of a group will be assigned in the beginning of thelab works.
· It is clear that employers look for persons who have excellent oral and written communicationskills. Therefore, all parts of the reports should be written in complete sentences using goodtechnical English. Substandard writing may reduce the score for the reports by up to 50%.
Please remember to use a dictionary (or the spell-checker in the word processor), proofreadthe report, and revise it if necessary. Please strive to achieve a professional quality in thesebrief reports. Sloppiness, lack of organization, scribbled notes, etc. will result in lower grades.
Scheduled ExamsThere will only be the final exam for this course. The final exam will be comprehensive and willcover the contents covered in the entire class.
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Grading PolicyThe final letter grade will be computed using the following criteria:
· Lab Reports/Projects/Laboratory Neatness/Participation 40%
· Mid-Term I Exam (October 1) 20%
· Mid-Term II Exam (November 12) 20%
· Project Report and Presentation
(Final Exam) (December 17) 20%
Letter Grades
· A+
(> 97%) A (93 – 96.9%) A-(90 – 92.9 %)
· B+
(87 – 89.9%) B (83 – 86.9%) B-(80 – 82.9 %)
· C+
(77 – 79.9%) C (73 – 76.9%) C-(70 – 72.9 %)
· D+
(67 – 69.9%) D (63 – 66.9%) D-(60 – 62.9%)
· F (< 60%)
Honor Code
· “California State University, Fullerton's Honor Code” explained in UPS 300.021 applies to allworks performed in this class including homework, quizzes, and examinations. Students should
strictly follow those codes.· This is a professional course. A learning environment will be created in each class for motivated
students; therefore professional conduct is expected of all participants. Professional conductextends to use of cell phones, personal computers, iPods and PDAs during lecture. Studentsviolating such professional conducts are subject to expulsion from the class.
· Students should strictly follow the safety regulations mentioned by the instructor. Studentsviolating the safety regulation will not be allowed to conduct the lab on that particular day and willbe counted as absent.
Drop PolicyThe Fall 2013 Schedule contains the University Regulations and Deadlines for dropping thiscourse. Students should note that the department stamp and/or department chair’s signature isalso required in addition to instructor’s signature to drop the course.
Students with Special NeedsStudents who need adaptations or accommodations because of a disability (e.g. learning,attention deficit disorder, psychological, physical, etc.), or have emergency medical information toshare with the instructor, or need special arrangements in case the building must be evacuated,are requested to make an appointment to discuss their needs with the instructor during the firstweek of classes.
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Detailed Class Schedule
Week Day Topic/s Section in Textbook Report Due
1 August 27Course Introduction andGuidance on Report Writing
Handout & 1
2 September 3Sieve and Hydrometer
Analysis, Specific GravityTest
3, 4, & 5
3 10Liquid Limit, and PlasticLimit Tests
6 & 7
5 17 Soil Classification 9
6 24Standard/ModifiedCompaction Tests
12 & 13Report 1:
Classification of Soil
9 October 1 Mid – Term Exam I Report 2:
Compaction
7 8Constant and Falling HeadPermeability Tests
10 & 11
8 15 Direct Shear Test 15 Report 3:Permeability
9 29 Stage Consolidation Test 17Report 4:
Direct Shear
10 November 5 Stage Consolidation Test 17
11 12 Mid – Term Exam II Report 5:
Consolidation
12 19Unconfined CompressionTest
16
13 November 25-29 Fall Recess No Class
14 December 3 UU Triaxial Test 18Report 6:UC Test
15 10 Slope Stability Analysis &Design
Handout Report 7:UU test
16 17 FINAL EXAM (GroupPresentation)
Group Report
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Emergency Procedures Notice to Students
The safety of all students attending California State University Fullerton is of paramountimportance. During an emergency it is necessary for students to have a basicunderstanding of their personnel responsibilities and the University’s emergency responseprocedures. In the event of an emergency please adhere to the following guidelines
Before an emergency occurs-
1. Know the safe evacuation routes for your specific building and floor.2. Know the evacuation assembly areas for your building.
When an emergency occurs-
1. Keep calm and do not run or panic. Your best chance of emerging from anemergency is with a clear head.
2. Evacuation is not always the safest course of action. If directed to evacuate, take allof your belongings and proceed safely to the nearest evacuation route.
3. Do not leave the area, remember that faculty and other staff members need to beable to account for your whereabouts.
4. Do not re-enter building until informed it is safe by a building marshal or othercampus authority.
5. If directed to evacuate the campus please follow the evacuation routes establishedby either parking or police officers.
After an emergency occurs-
1. If an emergency disrupts normal campus operations or causes the University to closefor a prolonged period of time (more than three days), students are expected tocomplete the course assignments listed on the syllabus as soon as it is reasonably
possible to do so.2. Students can determine the University's operational status by checking the
University's web site at http://www.fullerton.edu, calling the University's hotline
number at 657-278-0911, or tuning into area radio and television stations. Studentsshould assume that classes will be held unless they hear or read an official closureannouncement.
EMERGENCY CALLS
DIAL 9-1-1
All campus phones and cell phones on campus reach theUniversity Police Department
Non-emergency line: (657) 278-251524-hour recorded emergency information line: (657) 278-0911
(657) 278-4444
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CALIFORNIA STATE UNIVERSITY, FULLERTONCollege of Engineering and Computer Science
CIVIL AND ENVIRONMENTAL ENGINEERING DEPARTMENT
EGCE 324L Soil Mechanics Laboratory(Fall 2013)
LABORATORY SAFETY GUIDELINES
Introduction
Laboratory safety awareness is an important mindset that protects people, expensive equipment,
and the university resources while conducting laboratory experiments. Individuals working in the
Soil Mechanics Laboratory (EGCE 324L) facilities are always required to exhibit maturity and follow
proper operation procedures while operating equipment and conducting laboratory tests. This
responsibility implies upon entering the laboratory. The guidelines given herein are intended to
minimize personal accidents and equipment damage. Please be sure to follow the following four
mandatory rules while conducting the laboratory works.
v If you are not sure about what and why you are doing any task, please ask your
instructor.
v While conducting a lab experiment, safety of yourself and that of those around you are
paramount – make sure that everyone around you is aware of what is going on.
v Please do not leave any equipment unattended. Pack each equipment properly after
washing it and return to its original position.
v Please do not touch anything in the laboratory that is not a part of the experiment/s you
are conducting.
Laboratory Dress
While attending a laboratory task for this course, you must be appropriately attired for the
particular work related to the lab work. Some of the simple guidelines include:
v Wear sensible closed-toed shoes or boots; open-toed shoes, sandals, or bare feet are not
acceptable laboratory attire.
v Wear long pants; shorts and skirts are not acceptable laboratory attire.
v Refrain from wearing clothing accessories that may become caught in laboratory equipment.
v Put long hair in a ponytail or contain properly.
v Wear eyeglasses or contacts, if needed.
v Use safety glasses and ear plugs, when necessary.
v Wear gloves, face masks, protective shoes or boots, as appropriate, depending upon the
nature of the lab work.
Laboratory Procedures
A wide variety of equipment and testing apparatus reside in the laboratory. The complexity of
many of these devices necessitates specific care and consideration while operating them. If there
is any doubt or any question on operating any piece of equipment while performing laboratory work,
consult with the instructor or the lab technician.
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Guidelines for laboratory safety are necessary to minimize accidents and to ensure that expensive
equipment is not damaged by carelessness or negligence. The following are some of the basic rules
pertinent to lab safety:
v Turn on the lights upon entering the laboratory. Turn off the lights if you are last to leave
the laboratory.
vDo not handle any materials or operate any equipment unrelated to the EGCE 324Llaboratory experiment to be performed on that particular day.
v Never operate any unfamiliar equipment without a specific approval of the instructor or the
lab technician.
v Be sure to clean and dry out the equipment after you are done with the experiments.
v When operating very important equipment, be sure that at least two persons are always
present.
v Be careful while using and storing sharp edge equipment like knives.
v No food or beverages are allowed in the laboratory.
v No smoking is permitted in the laboratory.
v Be aware of your surroundings. Keep fingers away from large machinery.
vWear appropriate clothing and shoes.
v Place all laboratory equipment in their proper storage area after use.
v Always follow a professional manner.
Accidents
v In case of any type of accident and/or if someone is hurt, seek help immediately. Behave as
a responsible citizen in case of serious accidents and report to the concerned authorities.
If such thing happens, call the instructor immediately (301-310-4628). If the instructor is
not available, call lab technician (657-278-3134) or Civil Engineering Office (657-278-
3012).
v If equipment is damaged, please report the situation to the instructor promptly. This will
assure a proper and quick repair or replacement.v In the event of major fire, please evacuate the building immediately and seek professional
help (university police: 657-278-2515). In the event of a minor fire, use the nearest fire
extinguisher to extinguish the flame and/or seek the assistance of the instructor (301-310-
4628) and/or lab technician (657-278-3134).
Security
Proper security of the laboratory facilities also ensures a safe working environment. The following
are some of the guidelines:
v If you are the last to leave the laboratory room, please lock and close the doors and
windows prior to your departure.
v After you have finished using any equipment, please return it to its proper storage area andcabinet.
v Report any suspicious individuals or unwanted visitors not related to the laboratory to the
lab technician (657-278-3134) or university police (657-278-2515).
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ACKNOWLEDGEMENT OF RECEIPT FORM
EGCE 324L Soil Mechanics Laboratory(Fall 2013)
LABORATORY SAFETY GUIDELINES
Acknowledgement of Receipt
I hereby acknowledge that I have read the entire guidelines mentioned above regardingthe proper procedures and conduct to be followed in the laboratory experiments for SoilMechanics Laboratory (EGCE 324L). As a student at California State University,Fullerton, I understand these guidelines and procedures and agree to abide by them.
Course Title: Soil Mechanics Laboratory (EGCE 324L)
Term/Year: Fall 2013
Name:
Signature:
Date:
Please submit this form, completed and signed, to your instructor by the end of the first
laboratory period. Failure to do so will result in an incomplete grade for the term.
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GRAIN SIZE DISTRIBUTION ANALYSISSIEVE ANALYSIS
Application
Grain size distribution analysis is used to classify soils for engineering purposes, andother geotechnical applications, such as, filter design and other applications
mentioned at the bottom of the manual. ASTM D422 explains about the procedure
of grain size distribution analysis. Grain size distribution is done with sieve analysis
and/or hydrometer analysis. This chapter deals with the sieve analysis only.
EquipmentSieves (US sieve No. 4, 10, 20, 50, 100, 200)
A bottom pan and cover
Scale capable of measuring to the nearest of 0.01g
Mechanical sieve shaker
Stop watchEmpty bowl
Brush
Procedurei. Measure weight of an empty bowl.
ii. Collect approximately 500 g of a representative oven dry soil specimen, finer
than 4.75 mm.
iii. Break the soil samples into individual particles by hand or any other tool such as
mortar and pestle.
iv. Pour the soil into the bowl and weigh the mass of soil and bowl.
v. Prepare a stack of sieves, largest size sieve at the top and smallest sieve size
at the bottom. US No. 4 sieve should be at the top and US No. 200 sieve should
be at the bottom. Set the pan below the No. 200 sieve.
vi. Pour the soil into the top sieve, and cover it.
vii. Put the assembly into a mechanical shaker, tighten all the screws, and turn the
shaker on.
viii. Shake the assembly for about 5 minutes.
ix. Wait for about 3 minutes, and remove stacks of sieve.
x. Weigh the soil mass that is retained on each sieve and the bottom pan. For this,
empty the bowl and measure its weight. Fill the bowl with the soil retained in
each sieve. Then measure the weight of the bowl and soil. Populate the table 1.
xi. Sum up the quantity of soil retained on each sieve and the pan. If the total
weight is less than the initial weight by more than 1%, repeat the procedure.
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Calculations1. Calculate the % of soil retained on the ith sieve
Ri = 100,
,Re
W MassTotal
W tained Mass i
2. Calculate the cumulative % of soil retained on the ith sieve
i R
ii
i
i R1
3. Calculate the % of soil passing through the ith sieve
% finer =
ii
i
i R1
100
4. Populate the attached table completely using the above equation.
5. Make a graph of particle size in mm (log scale) in X-axis and % finer (in
arithmetic scale) in Y-axis using the graph paper shown in figure 1. You can use
your own “excel spread sheet” or other computer programs to make this graph.
6. Determine D10, D30, and D60 from the graph, which correspond to the particle
size for 10% finer, 30% finer, and 60% finer. Determine the D50, D15, D85, and
D90 also.
7. Calculate uniformity coefficient (Cu) and coefficient of gradation (Cc) using the
following equations.
10
60
D
DC u
1060
2
30
D D
DC c
Note:
D10 is also called effective size and is used to estimate coefficient of permeability.
Cu shows whether the soil is well graded or poorly graded.
Cc complements Cu to evaluate whether the soil is well graded or poorly graded, or
gap graded. They are used for Unified Soil Classification System (USCS).
D90, D15 and D85 are used to design filters. D50 is used in liquefaction analysis.
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Particle Size Analysis Procedure
Tested by: Tested Date:
Lab Partners/Organizations: Group:
Client: CSUF CEED Project: EGCE 324 L
Boring No.: N/A Recovery Date: N/A
Soil description:
Sieve shaking method/duration:
Total sample mass before sieving (Wtotal):
Total sample mass after sieving (Wtotal’):
% soil loss during sieving:
Table 1 Lab measurement data for particles size analysis
Sieve
No.
Sieve
Opening(mm)
Mass of Soil Retained
on Each Sieve, Wi (g)
% of Mass Retained on
Each SieveRi
Cumulative %Retained,
i R
% Finer
100- i R
4
10
20
40/ 50
100
200
Pan
% Loss during sieving = 100
'
total
total total
W W W
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Figure 1 Gradation sheet to plot the grain size distribution curve
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HYDROMETER ANALYSIS (ASTM D 422)
ApplicationHydrometer analysis is done to measure the proportion of particles smaller than
0.075 mm.
EquipmentASTM 152H Hydrometer
Mixer cup
Two 1000 cc graduated cylinder
Thermometer
Constant Temperature Bath
Sodium hexametaphosphate
Spatula
Beaker
BalanceSqueeze bottle
Rubber Stopper
Procedurei. Combine 50g (Md) of the soil passed through #10 sieve with 125 ml of sodium
hexametaphosphate solution (4%) in a 250 ml glass beaker. Allow the mixture to
soak for 16 hours (for demonstration today, 30 minutes will be enough ).
ii. Transfer all of the mixtures to an ASTM D422-specified dispersion cup. Wash
all the soil solids from inside of the beaker into the dispersion cup. Fill the cup
with water (half of the cup).
iii. Stir the mixture with a mechanical stirrer at the rate of 10,000 rpm for oneminute.
iv. Pour the slurry into a 1000 ml etched cylinder and fill with distilled water to
just below the etch mark. Wash all the slurry from cup into the cylinder using
squeeze bottle.
v. Using a rubber stopper, mix the soil water mixture by turning it upside down and
back at a rate of 1 turn per second for 1 minute.
vi. Set the cylinder on a water bath (or table) and start the timer immediately.
Wash the remaining soil off the stopper and lip of the cylinder with the squeeze
bottle and fill the cylinder to the etch mark with distilled water.
vii. Insert the hydrometer slowly and take the first hydrometer reading at 2 min,
with subsequent readings at 5, 15, 30, 60, 240, and 1440 minutes. Thehydrometer reading is taken at top of the meniscus.
viii. Remove the hydrometer after each reading, and place it in a 1000 ml cylinder
filled with distilled water between readings. Spin the hydrometer in the water-
cylinder to take off the adhered soil particles.
ix. Record the temperature of the mixture.
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Calculations1. Calculate diameter of particle at time t.
t
Lk D
K can be calculated for given Gs and temperature using Table 1.
L (in cm) = 16.3 – 0.163 R
2. Percentage passing for the specific diameter is calculated as,
%100)(
'
d M
ab R P
Values of a and b can be calculated using Table 2.
3. Calculate overall % passing as,
40#' P P P
Table 1 Value of K for different Gs and Temperature
Table 2 Values of Correction Factors a with Gs
Gs a
2.5 1.03
2.55 1.02
2.6 1.01
2.65 1.00
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2.7 0.99
2.75 0.98
2.8 0.97
2.85 0.96
Table 3 Values of Correction Factors b with temperature
Temperature
(oC)
b
17 5.9
18 5.6
19 5.3
20 5.0
21 4.7
22 4.4
23 4.1
24 3.8
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GRAIN SIZE ANALYSIS – HYDROMETER MEASUREMENT (ASTM D422)
LABORATORY DATA SHEET
I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization: Group
Client: CSUF CEED Project: EGCE 324L
Boring no.: N/A Recovery depth: N/A
Recovery date: N/A Recovery method: N/A
Soil description:
II. TEST DETAILS
Hydrometer manufacturer/serial no.:
Mixer manufacturer/serial no.:
Scale type/serial no./precision:
Duration of initial soaking period:
Concentration of sodium hexametaphosphate solution: 4%
Dry mass of soil used ( M d ):
Specific gravity of soil solids: Temperature:
K: a: b:
Notes, observations, and deviations from ASTM D422 test standard:
II I. MEASUREMENTS AND CALCULATIONS
Clock Time
(hh:mm:ss)
t
(min)
R L
(cm)
D
(mm)
P’
(%)
P
(%)
IV. EQUATION AND CALCULATION SPACE
L = 16.3 – 0.163 R t / L K D
100% x M
a )b R( ' P
d
P = P’(P -#40 )
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SPECIFIC GRAVITY TEST (ASTM D 854)Application
Specific gravity of soil is important in hydrometer analysis, weight volume related
calculations, etc.
Equipment500 ml etched flask
Squeeze bottle
Scale capable of measuring to the nearest of 0.01g
Thermometer (minimum 0.50C capacity)
Funnel
Vacuum supply stopper
Vacuum supply
Procedure
i.
Take approximately 60 g of dry soil and take exact weight measurement (M o).ii. Fill the flask up to the etch line with distilled water and measure weight (M a).
iii. Pour half of the water out of the flask and place the soil in the flask with a
funnel.
iv. Wash the soil down the inside neck of the flask.
v. Connect the flask to the vacuum source with the hose and stopper and apply
vacuum for 30 minutes, occasionally agitating the mixture.
vi. Fill the flask to the etch line with distilled water and weigh it (Mb).
vii. Record the water temperature in the flask.
Calculations
1. Calculate specific gravity (Gs) using the following equation.
)(0
0
ba
s M M M
M G
2. Apply the following temperature correction factor and calculate the Gs value for
200C.
K GG s s .20
Table 1 Temperature Correction Factor (K)
Temperature (0C) Correction Factor (K)
17 1.0006
18 1.000419 1.0002
20 1.0000
21 0.9998
22 0.9996
23 0.9993
24 0.9991
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SPECIFIC GRAVITY OF SOIL SOLIDS (ASTM D854)
LABORATORY DATA SHEET
I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization: GroupClient: CSUF CEED Project: EGCE 324L
Boring no.: N/A Recovery depth: N/A
Recovery date: N/A Recovery method: N/A
Soil description:
II. TEST DETAILS
Vacuum level: Duration vacuum applied:
Flask volume:
Scale type/precision/serial no.:Notes, observations, and deviations from ASTM D854 test standard:
III. MEASUREMENTS AND CALCULATIONS
Test ID
Mass of flask filled with water (M a )
Mass of flask filled with soil and water (M b )
Mass of dry soil (M o )
Specific gravity of soil solids (G s )
Water temperature
Correction factor (K )
Specific gravity of soil solids at 20oC (G s20 )
IV. EQUATION AND CALCULATION SPACE
) M M ( M
M G
bao
o s
G s20 = G s K
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LIQUID LIMIT
ApplicationLiquid limits are used to classify soil, correlate various soil properties with strength,
estimate swelling potential of soil, and hundreds of similar uses in geotechnical
engineering.
EquipmentCasagrande Liquid Limit Device
Grooving tool
Moisture cans
US No. 40 sieve
Distilled water
Plastic squeeze bottle
Scale
Ceramic soil mixing bowlOven
Frosting knife/spatula
Procedure3. Determine mass of the moisture can (W1).
4. Put about 300 g of air dry soil, passed through No. 40 sieve into a ceramic bowl and
add distilled water from plastic squeeze bottle. Mix the soil for some time to form a
uniform paste. (It is worthy to soak the sample with water for 48 hours before the
test, but we don’t have enough time in our lab to do so).
5. Place a portion of the paste in the brass cup of the liquid limit device. Smooth the
surface of the soil in the cup with spatula (keep maximum depth of soil in the cup toabout 8 mm).
6. Cut a groove along the center line of the soil pat in the cup.
7. Turn the crank of the liquid limit device at the rate of about 2 revolutions per
second. Drop height should be exactly 1.0 cm – check it. Closely observe the groove.
8. Count the number of blows (N) to close the grove over a length of 0.5 inches.
9. If N is more than 35, add some water into the soil, mix it and repeat the procedure.
If N is between 25 and 35, note the value of N and transfer a portion of the paste
to a moisture can and weigh (W2).
10. Clear the soil from the cup, wipe out the cup, and mix the soil with water. Repeat
the procedure until the grove is closed at 20-25 blows/cranks. Transfer the soil to
the moisture can and weigh. Repeat the procedure again to get the grove closed at15-20 blows. Although 3 tests are enough to get the desired value, it is advisable to
conduct 5 different tests to give N ranging from 12-35.
11. Put all moisture cans into the oven and dry them to a constant mass. Weigh the mass
of dry soil plus the can (W3) after 24 hours.
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Calculations
12. Calculate the moisture content of the soil.
Moisture content (w%) = 10013
32
W W
W W
13. Plot a graph for moisture content at Y-axis and Number of blows (in log scale ) at X-axis. The points will end up with a straight line with negative slope. This line is called
a flow line. Calculate the magnitude of the slope of the flow line. This slope is called
flow index.
14. Using the equation of flow index, calculate the moisture content for 25 blows.
15. Liquid limit is the value of w% at 25 blows.
Note:
The slope of the flow line will give Log (N), and we need to convert it to N while
calculating the values. Or you can use ‘excel spreadsheet’ to plot the result and
derive the value of N.
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Liquid Limit Test Results
Tested by: Tested Date:
Lab Partners/Organizations:
Client: CSUF CEED Project: EGCE 324L
Boring No.: N/A Recovery Date: N/A
Soil description:
Oven temperature: Drying time:
Precision of scale: Note:
Table 1 Measurement data for the water content of the particular test and corresponding N
Test No. 1 2 3 4 5
Can No.
Mass of can, W1 (g)
Mass of can + moist soil, W2 (g)
Mass of can + dry soil, W3 (g)
Moisture content, w%
Number of blows, N
Flow Index:
Liquid Limit:
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50
40
30
20
10
0
M o i s t u r e C o n t e n t , w ( % )
3 4 5 6 7 8 9
102 3 4 5
Number of Cranks
Figure 1 Graph to plot number of blows and corresponding moisture content.
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PLASTIC LIMIT
ApplicationPlastic limits are used to classify soil, correlate various soil properties with strength,
estimate swelling potential of soil, and hundreds of similar uses in geotechnical
engineering.
EquipmentSpatula/Frosting knife
Moisture cans
US No. 40 sieve
Distilled water
Plastic squeeze bottle
Scale
Ceramic soil mixing bowl
OvenFrosted glass plate
Procedure16. Determine mass of the moisture can (W1).
17. Put about 100 g of dry sample passed through US No. 40 sieve, into a ceramic soil
mixing bowl.
18. Add distilled water and mix it thoroughly to make a number of sticky mud-balls.
19. Take a ball of size slightly bigger than a pea-size, and roll it on the frosted glass
plate using the palm of your hand to form a thread of 3.18 mm diameter,
approximately (the exact size rod is provided to you). Then break the soil to several
pieces and repeat the procedure to make the thread.20. If the thread crumbles exactly at the diameter of 3.18 mm, transfer the thread
into the can and weigh (W2).
21. Put the can into the oven, weigh it after 24 hours when it is dry (W3).
22. Populate table 1.
23. Repeat the above mentioned procedure for at least 5 times, although 3 samples are
enough to get the plastic limit.
Calculations24. Calculation of the moisture content of the soil.
Moisture content (w%) = 10013
32
W W
W W
25. This moisture content is the plastic limit. Average value of three or more acceptable
tests is considered as the plastic limit of the soil.
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Plastic Limit Test Result
Tested by: Tested Date:
Lab Partners/Organizations:
Client: CSUF CEED Project: EGCE 324 L
Boring No.: N/A Recovery Date: N/A
Soil description:
Oven temperature: Drying time:
Precision of scale: Note:
Table 1 Measurement of moisture content for different soil specimens.
Test No. 1 2 3 4 5
Can No.
Mass of can, W1 (g)
Mass of can + moist soil, W2 (g)
Mass of can + dry soil, W3 (g)
Moisture content, w%
Average Plastic Limit, %
Plasticity Index*:
*Plasticity Index (PI) = LL - PL
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SOIL CLASSIFICATIONApplication
A classification scheme provides a method of identifying soils in a particular group
that would likely exhibit similar characteristics. Soil classification is used to specifya certain soil type that is best suitable for a given application. There are several
classification schemes available. Each was devised for a specific use. For example
American Association of State Highway and Transportation Officials (AASHTO)
developed one scheme that classifies the soil according to their usefulness in roads
and highways. However, Unified Soil Classification System (USCS) was originally
developed for use in airfield construction, but was later modified for general
purpose. AASHTO and USCS are two major classification systems in use.
Information needed
Grain size distribution curve
Plasticity information of the soil – LL, PL, and PIASTM D 2487
AASHTO M 145
Procedure
USCS Classification
26. Determine the % of soil retained on #200 sieve (R200).
27. If R200 is greater than 50%, it is a coarse grained soil otherwise it is a fine grained
soil.
28. For fine grained soil:
a. Find whether the soil is organic, by comparing the liquid limit of oven driedspecimen with that of the original specimen. If the LL of oven dried
specimen is less than 75% of that of the non oven dried specimen, the soil is
organic. Otherwise, the soil is inorganic.
b. Plot the LL and PI values on the plasticity chart, and find the group symbol
for the soil.
c. Determine % of soil retained on the US #4 sieve (R4). This is the % of
gravel fraction (GF) in the soil.
d. Determine the % of sand fraction (SF) in the soil by, SF = R200 – GF.
e. Use the ASTM table to classify the fine grained soil.
29. For coarse grained soil,
a. If % of gravel is more than % of sand, it is gravelly soil otherwise sandy.b. Using the grain size distribution curve, calculate Cc, and Cu.
c. Using the ASTM chart for the coarse grained soil, classify the soil. Be
careful to check whether they fall under dual classification or not.
AASHTO Classification
1. Determine the % of soil passing through #200 sieve (F200). If F200 is more than
35% soil is fine grained otherwise coarse grained.
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2. For coarse grained soil:
a. Determine F10, F40, F200, LL, and PI.
b. Match the soil group based on the AASHTO Classification.
3. For fine grained soil:
a. Determine LL, and PI.
b. Group soil according to the AASHTO classification.4. Determine Group Index (GI) of the soil as:
Group Index : GI = (F-35)(0.2+0.005(LL-40)) + 0.01(F-15)(PI-10)
5. Express GI in whole number.
6. Express the classification first by soil classification and then GI in parenthesis.
Calculations
30. Calculate the % of soil retained on the #200 sieve
R200 = (100 – F200)
31. Calculate the % of soil retained on the #4 sieve
R4 = (100 – F4)
32. Calculate uniformity coefficient (Cu) and coefficient of gradation (Cc) using the
following equations.
10
60
D
DC u
1060
2
30
D D
DC c
33. Calculate Group Index (GI)
GI = (F-35) (0.2+0.005 ( LL-40 ) ) + 0.01 (F-15) (PI-10)
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Classification of Soil
A classification scheme provides a method of identifying soils in a particular group that
would likely exhibit similar characteristics. Soil classification is used to specify a certain
soil type that is best suitable for a given application. There are several classification
schemes available. Each was devised for a specific use. For example American Association of
State Highway and Transportation Officials (AASHTO) developed one scheme that
classifies the soil according to their usefulness in roads and highways. However, Unified Soil
Classification System (USCS) was originally developed for use in airfield construction, but
was later modified for general purpose.
USCS
The USCS uses symbols for the particular size group:
G – Gravel particles retained on #4 sieve (4.75 mm)
S- Sand particles passing #4 sieve, but retained on # 200 sieve (0.075 mm)M- Silt particles passing # 200 sieve
C- Clay particles passing # 200 sieve
These are combined with other symbols with expressing gradation characteristics
W- Well graded
P- Poorly graded
And, plasticity characteristics (figure 1)
H – High plasticity L- Low plasticity O- Organic matter
Figure 1 Plasticity chart for the USCS classification of fines
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Figure 2 USCS Classification Chart
AASHTO Soil Classification System
The AASHTO soil classification is used to determine the suitability of soils for earthworks,
embankments, and road bed materials (sub base and sub grade). According to AASHTO
classification,
Gravel 75 mm – 2 mm (#10 sieve)
Sand 2 mm – 0.075 mm (#200 sieve)
Silt and Clay <0.075 mmSilty: PI <10%
Clayey: PI >11
AASHTO classification classifies soil into 7 major groups: A-1 through A-7.
A-1 – A-3 : Granular or coarse grained soil
A-4 – A-7 : Silty clay or fine grained soil
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Figure 3 AASHTO soil classification chart
Silty and clayey soils can be located in a plasticity chart as shown in the figure below.
Figure 4 Plasticity chart for the AASHTO classification system
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A group index value (GI) is appended in parentheses to the main group to provide a measure
of quality of a soil as highway sub grade material. The group index is given as:
Group Index : GI = (F-35) (0.2+0.005 ( LL-40 ) ) + 0.01 (F-15) (PI-10)
Where,F = % finer than #200 sieve size.
GI is expressed in a nearest whole number. If GI is less than 0, set it to 0. If any terms in
the above equation are less than 0, set them to 0. For them partial group index is used. The
higher the group index, the lower the quality of soil as sub grade material. GI should not
exceed 20 for any of group A-4 through A-7.
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LABORATORY COMPACTION TEST
Application
Compaction of soil is probably one of the largest contributors to the site work economy; inother words-it is important. Large sums of money are spent on it every day. Soil is a very
flexible and inexpensive construction material. It can be manipulated to produce a material
with a wide range of properties. Control of compaction in the field permits civil engineers
to engineer a soil to produce a material with properties that are optimized for a project.
Compaction is defined as the reduction in soil void ratio by expulsion of air from the voids.
In contrast, the consolidation process is the reduction of void ratio by expulsion of water
from the voids. These two processes are similar in that they result in a decrease in void
ratio. Compaction occurs instantly with application of a force. Consolidation is a time-
dependent process that can take many years to complete after a load is applied to soil.
Because compaction involves reducing the void ratio without changing the moisture content,the degree of saturation will increase.
Soil is compacted to improve the following soil properties and aspects of strength-
deformation behaviors:
Improve shear strength
Reduce compressibility
Decrease permeability
Reduce shrink/swell potential
Reduce liquefaction potential
Reduce compression due to wetting
The behavior of a soil during compaction and after compaction depends on:
soil type (fine vs. coarse grained)
compaction moisture condition
method of compaction
A variety of methods and machinery are used to compact soil.
Compaction of Fine-Grained Soils
When fine-grained soils are compacted they display a strong dependency on compaction
moisture content. Proctor (1933) described this behavior through the concept of the
"moisture – unit weight relationship ". This is also loosely (and unfortunately all too
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commonly) referred to as the moisture-density relationship even though the "density" is
actually unit weight.
It was found that, for any given amount of energy expended in compacting the soil, there
existed an optimum moisture where the dry density was greatest. This relationship is
shown in Figure 1 (from Hilf, Chapter 8. “Compacted Fill”, Foundation Engineering Handbook,
Fang, Editor, 1991).
The tests shown on Figure 1 are the result of two “Proctor compaction tests” on one soil. In
these tests, soil is compacted by a series of blows of a standard hammer in cylindrical molds
that have a known standard volume. The hammers are designed to provide a known,
repeatable input energy. Table 1 provides the details of each test. The complete moisture
– unit weight relationship is obtained by compacting soil at a series of different moisturecontents (but using the same effort each time). A smooth curve between the points is
drawn and the maximum dry unit weight and optimum water content are determined for a
soil at that compaction effort. The maximum dry unit weight is the peak point on the curve
and the optimum moisture content is the water content corresponding to that peak dry unit
weight.
Table 1. Details of Standard and Modified Proctor Tests.
Test Mold*
Volume
No. of
Layers
Blows/
layer
Hammer
Weight
Drop
Height
Energy
Input
Standard Proctor
(ASTM D 698)
1/30 ft3 3 25 5.5 lb 12 in 12,400
ft lb/ft3
Modified Proctor
(ASTM D 1557)
1/30 ft3 5 25 10 lb 18 in 56,000
ft lb/ft3
*4.0” diameter x 4.6” tall mold
The influence of standard effort vs. modified effort on the moisture-density relationship is
shown in Figure 1. Note as the compaction effort is increased, the maximum density
Figure 1 Moisture – unit weight relationships for a soil using two compaction efforts.
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G sw e
increases and the optimum moisture content decreases. The differences in the tests are in
the amount of energy transmitted to the soil with each hammer blow and are shown below.
To the left of optimum moisture the soil is referred to as “on the dry side”. Similarly,
points to the right of optimum (higher moisture contents) are referred to as “on the wet
side”.
Relative compaction is typically used as an index to compare the field density with the
laboratory density. Relative compaction is defined as:
Relative Compaction: %100max,
d
d RC
(1)
Where,
d = field density measured in the field
d, max = Proctor maximum dry density obtained from a Proctor Test.
This is expressed as a percentage.Note:
Relative compaction is based on dry unit weights . RC greater than 100% is possible.
The Zero Air Voids Line
The zero air voids (ZAV) line is the combination of moisture and density that produce
complete saturation of the soil or the d obtained when there is no air in the void spaces.
The compaction curve theoretically does not cross this line but becomes parallel to it.
Remember that the values of water content, wet unit weight, and specific gravity are not
constant throughout the soil. There could also be variability in the test results. Variability
can result in points on the compaction curve above the ZAV line (S>100%). These datapoints should not be thrown out.
Basic weight volume relationships are used to develop and equation for the ZAV line. Recall
that:
e
G
eV V
V G
V V
W
V
W w s
s s
sw s
v s
sd
1
Since S = 1 if the saturation is equal to 100 percent, the relationship:
can be substituted into the above equation to yield the final equation for the ZAV line:
w+ G
G
S
wS d
1
(2)
Note that G s and w are constants for a given soil. Therefore the ZAV line is a linear
function of water content. To draw the ZAV line, simply enter values of w and compute the
corresponding value of d .
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LABORATORY PROCEDURE (Modified Proctor)
Equipment
Compaction moldUS Sieve # 4
Modified Proctor Hammer
Balances sensitive to 0.01 lb, 0.1 g
Large flat pan
Jack
Steel straight edge
Moisture bowls
Drying oven
Plastic squeeze bottle with water
Procedure
1. Obtain approximately 5 lbs. of undried soil passing the No. 4 sieve for each test
being performed. A minimum of 5 tests is required, 6 is preferred.
2. Add enough water to each test sample to bring the water content within range
of optimum. Test samples should be prepared in approximately 2% increments.
First trial water content might be 4% (recommendation – 4%, 6%, 8%, 10% …).
3. Determine the weight (W1) and volume (V) of the Proctor compaction mold with
base plate (do not measure the extension). Use the scale sensitive to 0.1 lb to
determine the weight of the mold.
4. Determine the weight (Wtin) of the moisture bowls. Use the scale sensitive to.01 g to determine these weights.
5. Assemble and secure the mold and extension to the base plate. Spray lubricant
in it, which will help sample extrusion afterwards. Make sure that the apparatus
is placed on a rigid foundation (i.e., concrete slab). This is important not only for
safety reasons, but to ensure that the compaction effort is applied to the soil
and not the foundation.
6. Compact the first test specimen in the mold in five equal layers.
a. For the first layer, fill the mold about one third with loose soil.
b. Compact the lift with 25 blows of the compaction hammer. Make sure
that the hammer is kept vertical and the guide sleeve is not lifted. Also,
take care to evenly distribute the blows over the entire mold.
c. Score the top of the layer with a metal spatula.
d. For the second layer, fill up to two third level of the mold.
e. Repeat steps b and c.
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Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory)
f. For the final layer, fill to about the midpoint or higher of the extension.
This layer is important because after compaction, the top of the layer
must be equal to or above the top of the mold. If it is not the test must
be done over.
g. Repeat step b.
7. Remove the extension.
8. With the steel straight edge level off the sample so it is even with the top and
bottom of the mold. Take care not to create divots in the sample during this
process.
9. Determine the weight (W2) of the soil and mold plus base plate (not the
extension). Use scale sensitive to 0.1 lb. to determine this weight.
10. Take off the base plate and with the aid of the extruder, remove the sample
from the mold.
11. Collect a sample of soil from the center of the compacted soil and place it in themoisture tin.
12. Determine the weight (Wtin+soil) of the moisture bowl and soil.
13. Place the moisture bowl and soil in the oven over night to dry.
14. Repeat steps 5 through 13 for each of the remaining test specimens.
15. Determine the weight (Wtin+dry soil) of the tin and dry soil for each test specimen.
Calculations
Moisture Content
dry sampleWeight of
water Weight ofontent Moisture c , or
100
tindrysoil tin
drysoil tin soil tin
W W
W W w (3)
Moist Unit Weight
mold volume of
moist soil weight ofweight Moist unit , or
V W W 12 (4)
Dry Unit Weight
mold volume of
dry soil weight ofeight Dry unit w , or
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Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory)
1001
wd
(5)
Plot the compaction curve, d vs. w. Draw a best-fit curve, using a French curve so the curve
is smooth. Determine the optimum water content and maximum dry unit weight from the
curve.
Plot the zero air voids curve on the same plot as the compaction curve. Use a French curve
and plot at least 4 points to get the general shape of the curve. Plot the Zero Air Voids
Curve:
1001 s
w s
d wG
G
(6)
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Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory)
California State University, Fullerton
Department of Civil and Environmental Engineering
Soil Mechanics Laboratory
Modified
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EGCE 324L (Soil Mechanics Laboratory)
LABORATORY CONSOLIDATION TEST
Application
Settlement problems are actually two problems in one. Both the magnitude of
settlement and time rate at which this process occurs must be estimated on the
basis of laboratory tests. This laboratory will focus on the time rate of settlement
as it is often the most important aspect of the problem. This lab also focuses on
the pressure-settlement relations.
For instance, suppose it is proposed to build a highway embankment over soft soils.
The embankment places a load on the soil and depending on the thickness of soft soil
and size of the loaded area, the total magnitude of settlement computed may take
many tens of years to occur. Thus the project must wait for the settlement to
occur before construction of pavement sections can take place. There aretechnologies available that can speed up the rate of consolidation. These are
discussed in courses on Ground Modification .
Recall that a complete consolidation test involves loading a soil specimen in a series
of increments. From these data, a void ratio (e ) vs. log pressure curve is developed
and estimates of the total magnitude of settlement are made using the parameters
C c , C r and ’ p . Estimates of the time rate of settlement are made using the
Coefficient of Consolidation, C v , that is interpreted from plots of dial gage reading
(compression) vs. log time during individual load increments of a consolidation test.
C v is not a constant but varies with applied stress. As the stress level increases, the
void ratio decreases and permeability decrease thereby increasing the time required
for water to flow from the soil voids. Therefore, in an actual project, C v should beestimated for the actual range of effective stress expected in the field.
Equipment
Consolidometer set
Filter paper
Stop watch
Balance sensitive to 0.01 lb
Moisture cans
Drying oven
Procedure
You are provided with a trimmed soil specimen.
Measure height of specimen (Subtract the gap between top of the ring and
specimen) .
Take weight of the specimen with ring.
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Set a lower porous stone in the consolidometer. Set a filter paper on it. Then set
the soil specimen into the consolidometer. Set a filter paper and upper porous stone
on top of the specimen.
Set the upper platen on top of the porous stone.
Pour water from outer jacket and saturate the specimen for about 15 minutes. This
water level should be kept higher than the porous stone during the test.
Set a steel ball on top of the upper platen and the loading device on top of the ball.
All equipment are set with vertical displacement transducers. Record the initial
LVDT reading for your equipment.
Apply load to the specimen which will give vertical stress of about 7 psi.
Record the deflection dial gauge reading at 0 min, 0.25 min, 1 min, 2 min, 4 min, 6
min, 9 min, 12 min, 20 min, 25 min, 36 min, 60 min, 120 min, 240 min, 480 min, and
1440 min.
Increase the load to about 14 psi, and 28 psi, 56 psi, and 112 psi in every 24 hours
and repeat the same procedure. But just take the reading at 0.25 and 1440 minutefor those readings.
Next Thursday, increase the load to 222 psi and record the deflection at 0 min,
0.25 min, 1 min, 2 min, 4 min, 6 min, 9 min, 12 min, 20 min, 25 min, 36 min, 60 min, 120
min, 240 min, 480 min, and 1440 min.
After that reduce the load slowly and record deformation during unloading at the
end of 112 psi, 56 psi, 28 psi, 14 psi, and 7 psi.
You don’t need to note down intermediate values for the vertical loads other than 7
psi, and 224 psi. For other loads, just note the initial and final deflection.
Remove the soil specimen after 24 hours of the application of the vertical stress of
224 psi and measure final height of the specimen. Measure the weight of the specimen and put the entire specimen into the oven and
oven-dry them for 24 hours. Measure the weight after 24 hours. That will help you
to get void ratio.
Calculations
The lab reports shall include the following:
Sample calculations.
A plot of settlement versus the logarithm of time for the vertical stress of 7 psi
and 222 psi. Calculate settlement amount and time for 50% consolidation. Calculate
time for 50% consolidation.
A plot of settlement vs. square root of time for the vertical stress of 7 psi and 222
psi. Calculate settlement amount and time for 50% consolidation. Calculate time for
90% consolidation.
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Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory)
Determine the coefficient of consolidation, C v from the time rate data collected in
the lab. The calculations are presented below and most textbooks cover this in
detail.
Using the settlement data for 100% consolidation, calculate the void ratio (e) for
the corresponding stresses.
Plot a e-log ' graph and find out the pre-consolidation pressure.
EQUATION TO BE USED
w s
s
s AG
M H
(1)
s
s
H
H H e
0 (2)
Where,
Hs = Height of soil solidMs = Dry mass of the specimen
A = Area of the specimen
Gs = Specific gravity of the soil solid (take 2.68)
w = Density of water
H = Initial height of the specimen
e0 = Initial void ratio
For the first incremental loading, s H
H ee 1
01
(3)
Likewise for the second load increment, s H
H ee
202
(4)
Shown in figure 1 is an example of e-long curve.
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Civil & Environmental Engineering Department
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Determination of preconsolidation pressure ( ’p or P’p)
Figure 2 Method to determine pre-consolidation pressure
Figure 1 e-log curve
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Choose by eye the point of minimum radius of curvature on the e-logσ curve (point
A).
Draw a horizontal line through point A.
Draw a line tangent to the curve at point A.
Bisect the angle made by steps 2 and 3.
Extend the straight line portion of the virgin compression curve
up to intersect the bisecting line from step 4.
The intersection point gives the best estimate of preconsolidation pressure.
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ONE-DIMENSIONAL CONSOLIDATION TEST (ASTM D2435)LABORATORY DATA SHEET
I. GENERAL INFORMATION
Specimen prepared by: Date:
Lab partners/organization: USUFClient: CSUF Project: EGCE 324L
Boring no.: N/A Recovery depth: N/A
Recovery date: N/A Recovery method: N/A
Soil description:
II. TEST DETAILS
Load frame type/serial no.:
Scale type/serial no./precision:
Consolidation ring diameter: Initial specimen height, H o :
Consolidation ring mass: Specimen volume, V o :
Specific gravity of soil solids, G s : (take 2.68)
Notes, observations, and deviations from ASTM D2435 test standard:
III. MEASUREMENTS AND CALCULATIONS
Before Test After Test
Mass of moist soil + porous stone +Ring
Mass of moist soil M To = M Tf =
Mass of porous stone + Ring
Mass of dry soil M d = M d =
Mass of moisture
Moisture content w o = w f =
Void ratio e o = e f
=
Degree of saturation S o = 100% S f = 100%
IV. TEST DETAILS
Scale type/serial no./precision:
Load no.: Load increment, ’ :
Filter paper type:
Porous stone type, weight and thickness:
Machine deflection:
Deformation indicator type and conversion factor K (if applicable):
Notes, observations, and deviations from ASTM D2435 test standard:
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ONE-DIMENSIONAL CONSOLIDATION TEST (ASTM D2435)
TIME-DEFORMATION MEASUREMENTS
LABORATORY DATA SHEET
V. MEASUREMENTS AND CALCULATIONS ’ = 7 psi
Date
(mm/dd/yy)
Clock Time
(hh:mm:ss)
Elapsed Time
(min)
Raw Deformation( )
Deflection-CorrectedDeformation
( )
0.0
0.25
1
2
4
6
9
12
20
25
36
60
120
240
480
1440
’ = 14 psi
0.25
1440
’ = 28 psi
0.25
1440
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V. MEASUREMENTS AND CALCULATIONS
Date
(mm/dd/yy)
Clock Time
(hh:mm:ss)
Elapsed Time
(min)
Raw Deformation( )
Deflection-CorrectedDeformation
( )
’ = 56 psi
’ = 112 psi
’ = 224 psi
0.0
0.25
1
2
4
6
9
12
20
25
36
60
120
240
480
1440
Deformations while reducing load: 112 psi 56 psi 28 psi
14 psi 7 psi
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ONE-DIMENSIONAL CONSOLIDATION TEST (ASTM D2435)TIME-DEFORMATION PLOTTING USING THE LOG TIME METHOD
I. TEST DETAILS
Load no.: Load, ’ :
Initial specimen height, H o : Deflection units:Dial gauge conversion factor, K :
Notes, observations, and deviations from ASTM D2435 test standard:
II. MEASUREMENTS AND CALCULATIONS CALCULATION SPACE:
’ : d 100:
t 2: d 2:
t 1: d 1:
d: d o:
d 50: t 50:
H D50: cv:
III. EQUATIONS
From figure 3,t 1 = t 2/4 d = d 2 – d 1 d 0 = d 1 – d d 50 = (d 0 + d 100)/2
2
) K ( d H H 50o
50 D
or2
5050
d H H o
D
50
250 )0.197(
t
H c D
v
Time, t (log scale)
D e
f o r m a t i o n
, d
d 100
t 2t 1
d 0
d 1
d 2
d
d d 50
t 50
Figure 3 Deformation-Log time plot for the consolidation data
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ONE-DIMENSIONAL CONSOLIDATION TEST (ASTM D2435)TIME-DEFORMATION PLOTTING USING THE ROOT TIME METHOD
I. TEST DETAILS
Load no.: Load, ’ :Initial specimen height, H o : Deflection units:
Dial gauge conversion factor, K :
Notes, observations, and deviations from ASTM D2435 test standard:
II. MEASUREMENTS AND CALCULATIONS CALCULATION SPACE:
’ : d 0:
X : 1.15X :
d 90: t 90:
d 100: H D50:
cv:
III. EQUATIONS
From figure 4,
)(11.1 900100 od d d d 90
250 )(8480.
t
H c
Dv
D e
f o r m a t i o n
, d
Time, t (minutes; root scale)
x = (linear scale)
0 1 4 9 16 25 36 49 64 81 100 121
0 1 2 3 4 6 7 8 9 10 115
d-t curve
X
1 . 1
5 X
d 0
d 90
t 90
d 100
Figure 4 Deformation-square root of time plot for the consolidation data
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ONE-DIMENSIONAL CONSOLIDATION TEST (ASTM D2435)TIME-DEFORMATION PLOTTING USING THE ROOT TIME METHOD
PLOTTING PAPER
Elapsed time t (min)
S e t t l e m e n t S ( d i v i s i o n )
0 1 862 4 4010 907020 30 6050 1008010
1
4
1
2
1
250150 200 300
0 1 2 43 5 6 7 8 9 10 11 12 13 1514 16 17 18 19 20 21 2322cm0 1 2 43 5 6 7 8 9 10 11 12 13 1514 16 17 18 19 20 21 2322cm
D e f o r m
a t i o n (
)
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CONSTANT HEAD AND FALLING HEADPERMEABILITY TEST
Permeability is a measure of the ease in which water can flow through a soil volume. It isone of the most important geotechnical parameters. However, it is probably the most
difficult parameter to determine. In large part, it controls the strength and deformation
behavior of soils. It directly affects the following:
quantity of water that will flow toward an excavation
design of cutoffs beneath dams on permeable foundations
design of the clay layer for a landfill liner.
For fine grained soil Falling head permeability test is done, whereas constant head
permeability test is done for the coarse grained soil.
Application Estimation of quantity of underground seepage water under various hydraulic
conditions
Quantification of water during pumping for underground construction
Stability analysis of slopes, earth dams, and earth retaining structures
Design of landfill liner
Equipment
Combination Permeameter assembly
Stop watch
Graduated cylinder (250 or 500 ml)
Balance sensitive to 0.01 lbMoisture cans
Drying oven
Thermometer
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Figure 1 Sketch of the combination permeameter
Figure 2 Sketch of the combination permeameter assembly
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Figure 3 Sketch of the combination permeameter test: Falling head (left), constant head
(right)
Constant Head Permeability test
Procedure
The following steps are already done:
Mix sufficient water into the sample to prevent segregation of particle sizes during
placement into the Permeameter. Enough water should be added to allow the
mixture to flow freely, forming layers.
Remove both the chamber cap and upper chamber from the unit by unscrewing the
three knurled cap nuts and lifting them off the tie rods. Position one porous stone on the inner support ring in the base of the chamber.
Using a scoop or funnel, pour the prepared specimen into the lower chamber, using a
circular motion to fill the lower chamber to a depth of 1.5 cm. A uniform layer
should be formed.
Use an appropriate tamping device to compact the layer of soil to the desired
density. Repeat the compacting procedure until the sample is within 2 cm of the top
of the lower chamber section.
Replace the upper chamber section, placing the rubber gasket between the chamber
sections. Be careful not to disturb the test specimen. Continue the sample
placement operation until the level of compacted material is about 2 cm below the
rim of the upper chamber. Carefully level the surface of the specimen and place theupper porous stone on it.
Place the compression spring on the porous stone. Replace the chamber cap and
sealing gasket, securing it firmly with the cap nuts. The spring will restrict upward
sample movement.
Measure and record the sample length.
Assemble the constant head funnel, rod and meter stick. Use the rod clamp the
funnel's lower portion.
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Adjust the level of the funnel to allow the constant water level in it to remain a few
inches above the top of the specimen.
Connect the flexible tube from the tail of the funnel to the bottom outlet of the
Permeameter. Keep the valves on top of the Permeameter open.
Place a receiver at the top outlet to collect any water that may come out.
If preferred, a piece of tubing may be connected to the outlet, leading the water to
a sink.
Open the bottom outlet valve and allow water to flow into the permeameter.
As soon as water begins to flow out of the top control (deairing) valve, close the
control valve, letting the water flow out the outlet for a time.
Close the bottom outlet valve and disconnect the flexible tubing at the bottom.
Connect the constant head funnel to the top side port.
Open the bottom outlet valve and raise the constant level head (funnel) to a
convenient height to get a reasonable steady flow of water.
Accurately measure the vertical distance between the funnel overflow level and the
chamber outflow level.
Measure and record the length of the specimen, L.
You need to perform the following steps
Allow adequate time for the flow pattern and/or specimen to stabilize.
After equilibrium flow has been established, measure the time taken to have
specified volume of water flowing out. Use a measuring cylinder and a stop watch.
Repeat three or more times, calculating the average time.
Calculations
The lab reports shall include the following: Sample calculations.
Table showing the calculations pertinent to the permeability of the soil.
Average value of permeability
Calculate the void ratio by oven drying the specimen and taking the dry mass.
EQUATION TO BE USED
k =VL
Aht
(1)
Where,
K = Coefficient of permeability
V = Collected volume of water
L = Length of soil column
A = Area of the soil column (31.65 cm2)
h = Head difference
t = Time required to get V volume
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Falling Head Permeability test
Procedure
The following steps are already done: Compact the sample in the lower chamber section of the Permeameter, in layers
approximately 1.5 cm deep, to within about 2 cm of the lower chamber rim. Use an
appropriate tamping device to compact the sample to the desired density.
Remove the upper section of the chamber tie rods and place the upper porous stone
on the specimen, securing the upper section of the chamber with spring to the unit.
Measure and record the length of the specimen.
Use the clamp to attach the falling head burette to the support rod. Position the
burette as high as is possible for practicality. Place the meter stick directly behind
the burette, so the height of water in the burette above the chamber outflow port
may be read.
Saturate the specimen, following the steps outlined above. Measure the heights of the two levels from the outflow level.
You need to perform the following steps
After a stable flow has been established, note the drop in head (h) in 2 hours. (use
a stop watch).
Calculations
The lab reports shall include the following:
Sample calculations.
Table showing the calculations pertinent to the permeability of the soil.
Average value of permeability
Calculate the void ratio by oven drying the specimen and taking the dry mass.
EQUATION TO BE USED
k =At
aLln
1
0
h
h (2)
Where,
K = Coefficient of permeability
a = Area of the burette (1.695 cm2)
L = Length of soil column
A = Area of the soil column (31.65 cm2)
h0 = Initial height of water
h1 = Final height of water = h0 - h
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t = Time required to get head drop of h
Temperature Correction
C
C T
C T C k k
20
20
(14)
Where,
kToC = measured permeability at the actual water temperature in the lab
k20oC = permeability at the standard temperature of 20OC
Table 1 of Correction Factors for Water Temperature
Test Water
Temperature, T (C)
T C/20C Test Water
Temperature, T (C)
T C/20C
15 1.135 22 0.953
16 1.106 23 0.931
17 1.077 24 0.91018 1.051 25 0.889
19 1.025 26 0.869
20 1.000 27 0.850
21 0.976 28 0.832
29 0.814
Table 2 Typical permeability coefficients for different soils
Soil Type Typical Permeability, k (cm/sec)
Gravels and Coarse Sands > 10-1
Fine Sands 10-1 to 10-3
Silty Sands 10-3 to 10-5
Silts 10-5 to 10-7
Clays < 10-7
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HYDRAULIC CONDUCTIVITY OF GRANULAR SOIL
UNDER CONSTANT HEAD (ASTM D2434)
LABORATORY DATA SHEETI. GENERAL INFORMATION
Tested by: Date tested:Lab partners/organization:
Client: Project:
Boring no.: Recovery depth:
Recovery date: Recovery method:
Soil description: Sand
II. TEST DETAILS
Specimen diameter, D: 6.35 cm Specimen area, A: 31.65 cm
Specimen Length, L: Volume of soil, V:
Dry mass of soil, M s: Specific gravity of soil solids, G s: 2.65 Dry unit weight, d : Void ratio, e:
Scale type/serial no./precision:
Saturation method: Constant head Saturation duration: 48 hours
Specimen preparation method: Dry packing
Notes, observations, and deviations from ASTM D2434 test standard:
III. MEASUREMENTS AND CALCULATIONS
Test
No.
Head
Difference
h)
Hydraulic
Gradient
(i)
Flow
Volume
(Q)
Time
(t)
Flow Rate
(q)
Hydraulic
Conductivity
(k)
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HYDRAULIC CONDUCTIVITY OF GRANULAR SOIL
UNDER FALLING HEAD
LABORATORY DATA SHEET
I. GENERAL INFORMATION
Tested by: Date tested:Lab partners/organization:
Client: Project:
Boring no.: Recovery depth:
Recovery date: Recovery method:
Soil description: SM
II. TEST DETAILS
Specimen diameter, D: 6.35 cm Specimen area, A: 31.65 cm
Burette area, a: 1.695 cm2 Specimen length, L:
Dry mass of soil, M s: Volume of soil, V:
Specific gravity of soil solids, G s: 2.68 Dry unit weight, d :Void ratio, e: Scale type/serial no./precision:
Saturation method: Constant head Saturation duration: 48 hours
Specimen preparation method: Dry packing
Notes and observations:
III. MEASUREMENTS AND CALCULATIONS
Test No. Initial
Head
(H 0 )
Initial Hydraulic
Gradient
(ii)
Final
Head
(H 1 )
Time
(t)
Hydraulic
Conductivity
(k)
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CALCULATION OF SEEPAGE DISCHARGE AND SEEPAGE PRESSURE
Seepage discharge calculation
1. Sketch the coffer dam on scale.
2. Measure head difference (H).
3. Make flow net.
4. Find nf and nd from flow net.
5. Calculate seepage discharge
Q = b H
n
nk
d
f .. b = width of channel = 56 cm
For calculation, consider H = 20 cm.
Blowout of Coffer dam
Figure 1: Schematic diagram showing liquefaction potential zone
1. Calculate submerged unit weight of soil, ’.
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w s
e
G ).
1
1('
Take Gs = 2.65, e = 0.81
2. Calculate critical gradient, ic.
w
ci
'
3. Calculate head right at the bottom (A) and at D/2 distance from point A of the pile.
(D is the depth of the pile).
HA = ( H – ndA x H) HB = ( H – ndB x H)
ndA = number of head drops at A, H = head drop for each equi-potential line = H/nd
You get values in terms of H
4. )(2
1 B Aaverage H H H
5.
D
H i
average
6. In order to blowout the dam, i = ic
Calculate H for blowout with this.
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Seepage
Darcy’s law is applicable when flow of water is in one direction. In real world problems,
seepage occurs in all three dimensions. Solution for 3D problems is complicated and needs
advanced mathematical calculations. In many cases, 3D problems are simplified to 2D andseepage flow is calculated accordingly.
Equation of 2D Steady Flow
Conditions:
Darcy’s law is valid
K is same in all dimensions (homogenous material)
Figure 1 Flow through a 2-D system
Let’s consider a 2-D seepage flow system as shown in figure 1.
Darcy’s Law explains: Aik Q ..
At section X (for 1 m. strip), At section X+dX
1... dyik q x x 1... dyik q dx xdx x
At section Y (for 1 m. strip), At section Y+dY
1... dxik q y y 1... dxik q dy ydy y
As the flow is steady, net flow should be 0.
0)()( x ydx xdy y qqqq
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or 0)....()....( dxik dyik dxik dyik y xdy ydx x
or 0).().( dxiidyii ydy y xdx x (1)
But
x
hi x
and
y
hi y
dx x
iii x
xdx x .
and dy
y
iii y
ydy y .
Substituting these values in equation (1)
0....
dxdy
y
idydx
x
i y x
Or 0)()(
y
h
y x
h
x
Therefore, 02
2
2
2
yh
xh (2)
This equation is called Laplace Equation.
Solution for Laplace equation:
Analytical method (mathematical)
Numerical method (Finite Element, Finite Difference)
Flow models (sand, glass bead)
Analog model (electric, heat)
Graphical method (flow net)
Graphical method is discussed in this chapter.
Graphical Solution (Flow Net)
It is quick and simple.
No special equipment is needed.
Drawing improves understanding.
However, for complex problems, finite element is better.
Laplace equation requires 2 families of curves that meet at right angle. One is called flow
line and the other is called equi-potential line . The network of these lines is called “Flow
Net ” (figure 2).
Properties of flow net
Same flow quantity (q) through each flow channel.
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Same head drop (h) between each adjacent pair of equi-potential lines
(except for partial drop).
Figure 2 Example of flow net beneath a dam structureIn figure 2,
f n
qq (3)
d n
H h (4)
Seepage Calculation Using Flow Net
If our flow nets are going to have the properties of the lines mentioned above, we need
to draw them in a certain way.
Figure 3 Distribution of equi-potential lines in a flow channel
From figure 3,
Aik q .. = 1... bl
hk
=
l
bhk ..
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q and h should be the same for every element. Then,l
bmust also be the same for every
element.
l
b = side length ratio (same for all elements)
orl
b
n
H k
n
q
d f
..
Therefore,l
b
n
n H k q
d
f ...
i.e.l
b H k q .$.. (5)
where,d
f
n
n$
However, if we can makeb
l = 1 by making square flow net grid,
.$. H k q (6)
and Q = q. L
where, L is the length of dam in a perpendicular direction
Method of Drawing Flow Net
Identify boundaries
upstream and downstream surfaces are equi-potential lines as they
represent atmospheric pressure. Therefore, all flow lines intersect
them at right angle.
Body of impervious layer is a flow line, and equi-potential lines
intersect them at right angle.
Sketch 2 – 3 flow channels.
Sketch equi-potential lines.
Iterate, erasing and re-sketching lines to form “square” with l/b = 1. If
required check the square pattern by drawing a circle.
Perform seepage computation for q and then calculate Q.
Shown in figure 4 is an example of flow net under a sheet pile.
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Figure 4 Example of flow net and seepage calculation.
Note
For y x k k ,
we make horizontal scale = x
y
k
k x vertical Scale
and plot the structure. Then we follow the same procedure. This gives,
d
f
y xn
n H k k q
...
Use of Flow Net
Uplift pressure under hydraulic structure
From figure 5,
nd = 7 H = 7 m
Head Loss at each equi-potential line = 7/7 = 1 m
Head at A, i.e. hA = (9 – 1 x 1) = 8 m
Uplift pressure UA = 8. w
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Likewise, UB = 7. w
Figure 5 Calculation of uplift pressure
Method to determine pore pressure and uplift pressure Determine head at point where pore pressure is required.
Express the head as a value referred to the point itself as a datum.
Calculate pore pressure, UA = hA . w
Caution:
Most common mistake is to be inconsistent about datum.
Head = ( a value ) (referenced to) ( a datum )
To calculate a pore pressure, the best datum from the head is the point itself.
Count head either to head water or to tail water.
Effective stress = ’ = - u
If u = , ’ = 0 (We will have liquefaction )
At liquefaction, = uA
’. Z = i . w . Z
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Therefore,w
w s
w
e
G
i
1
)1(
' =
e
G s
1
1
This is called critical gradient (ic)
e
Gi sc
1
1 (7)
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11. Write a report based on the differences between the calculated seepage, head
to blowout the cofferdam, equi-potential line and flow net. Write your comment.
CalculationsAll pertinent calculations were supplied last week.
Seepage Discharge from one side2
1
Time
Volume Measured
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SEEPAGE INTO A DOUBLE WALLED COFFERDAM
Group:
Date:
A) Initial Head Difference cm
B) Seepage Quantity
Quantity Time (minute)
1.
2.
3.
4.
C) Head drop in equi-potential line
Point 1 cm
Point 2 cm
Point 3 cm
D) Blow out
Total head difference for blowout cm
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Measurement of Shear Strength Parameter of Soil with
irect Shear Test
Figure 1 Direct Shear Device
Advantages of Direct Shear Test
Simple, fast
Disadvantages of Direct Shear Test Cannot control pore pressures. Therefore tests are assumed to be drained.
Failure on horizontal plane only, which may not be the weakest plane.
Non-uniform stress conditions inside shear box.
Principal stress rotations occur
Vertical and horizontal stresses are principal stresses before shear.
Vertical and horizontal stresses are not principal stresses at failure.
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Figure 2 Shear Strength Envelop
ApplicationDirect shear test gives shear strength parameters (cohesion and friction angle) of
soil. Shear strength parameters are important in all types of geotechnical designs
and analyses.
Equipment
Strain controlled direct shear device with two displacement LVDT and a load cell
Balance sensitive to 0.1 g
Moisture cans
Oven
Procedure
1. Take the shear box, and set two vertical pins to keep the two halves of the
shear box together.
2. Set a porous stone at the base and fill the box with the dry sand (make 1 inchthickness). Compact the sand gently.
3. Set another porous stone on the top.
4. Set top platen on top of the porous stone.
5. Put the shear box assembly into the direct shear device.
6. Fill up the outer jacket with water.
7. Turn on the software and follow the instruction.
8. Apply dead load to the load hanger to make normal stress of approximately 50
kPa. You need to hold the cross bar to make it rest right on top of the top platen.
9. Remove both vertical pins.
10. Set up the dial gauges for vertical displacement and horizontal displacement.
Make sure that the shear box is connected to the electricity line and is on.11. Consolidate the specimen for 100% consolidation and apply horizontal load to the
box at the strain rate that is calculated based on the consolidation data. Set
that speed both in the computer and the shear box.
12. Record horizontal displacement, vertical displacement, and shear force at 15
seconds interval.
13. Shear stress increases, peaks and then drops or may remain flat. Once peak/or
maximum shear stress is attained, continue for a while and stop the test. Be
cautious not to let the shear box touch the wall of water jacket.
14. Take the sample out, take weight and put it into the oven to measure the water
content.
15. Take another specimen and repeat the procedure for the normal stress of 100kPa.
16. Take the third and fourth specimens and repeat the procedure for the normal
stresses of 150 kPa and 200 kPa respectively.
Calculations
17. Calculate area and volume of the specimen.
18. Calculate bulk unit weight of the specimen.
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Bulk unit weight ()=V
W
19. Calculate dry unit weight of the specimen.
Dry unit weight(d) = w1
20. Calculate initial and final void ratio.
e = 1d
w sG
take Gs = 2.65
21. Calculate normal stress (’)
Area
Load Normal '
22. Calculate shear stress.
Area
ForceShear
23. Plot versus shear strain (shear displacement/original height of specimen).
24. Plot vertical strain (displacement/initial height) vs shear strain.
25. Plot normal stress (in x-axis) vs shear stress for all tests.
26. The equation of the best fit line will give you c’ and ’.
Report
1. Submit all pertinent calculations and graphs.
2. Report the values of c’, and ’ based on four shear tests.
3. Present final void ratio vs shear stress ratio (/’).
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Soil Mechanics Laboratory
Direct Shear Test Laboratory Data Sheet
I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization:Client: CSUF Project: 324 Lab Direct Shear
Boring no.: NA Recovery depth: NA
Recovery date: NA Recovery method: NA
Soil description: Clean sand
II. TEST DETAILS
Sample length/width: 4 in. Sample Height:
Initial Sample Mass: Final Sample Mass:
Wet Mass of the Specimen: Dry Mass of Specimen:
Normal force, N : Normal stress, :
Deformation rate: Deformation indicator type: LVDTShear force measurement instrument type: Load cell
Horizontal dial gauge conversion factor, K H : 1
Vertical dial gauge conversion factor, K V : 1
Proving ring dial gauge conversion factor, K F : 1
III. MEASUREMENTS AND CALCULATIONS
Horizontal
Deformation
Reading
(GV )
Vertical
Deformation
Reading
(G H )
Force
Reading
(G F )
Horizontal
Displacement
(H)
Vertical
Displacement
(V )
Shear
Force
( F )
Shear
Stress
( )
Shear strength ( f ):
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Measurement of Shear Strength of Soil withUnconfined Compression Test
Shear Strength of Soil Shear strength of soil is the internal resistance of soil to shearing forces.
Determination of the shear strength of soil is one of the most important aspects of
geotechnical engineering. Ultimate shear strength and the deformation behavior of
soil under an applied load are critical for design of foundations, earth structures,
retaining structures, and many others. Shear strength is fundamentally due to the
combination of friction between particles and the work required to cause the sample
to change in volume, or: 1) Inter-granular friction, , and 2) Dilation, or volume
change, . Naturally, any factor which influences friction or volume change will
influence the strength of a specimen. The most influential factors (state
parameters) that affect volume change include void ratio and confining stress ( 3 ’).Grain shape and roughness are two factors that influence friction.
Shear strength at failure is normally defined by Mohr-Coulomb Failure criteria.
Mohr-Coulomb Failure criteria
Material fails with the combined effect of normal stress (n’) and shear stress ().
According to Mohr,
f = f ()
Figure 1 Mohr-Column Failure Envelope
In most of the soil mechanics problems, failure envelope is considered as a straight line,
given by the equation,
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tann failure c
Where,
c is the cohesion
is the angle of friction.
n is the normal stress on the failure plane at failure.
This equation is called Mohr-Coulomb Failure Criteria.
The strength parameters c’ and ’ are determined from the slope and intercept on a Mohr
diagram of a best-fit line tangent to a series of Mohr circles at failure. The influence of
inter-granular friction, dilation, and true cohesion are assumed to be represented by these
two parameters.
In saturated soil, = ’ + u and
'tan'' n failure c
Where,
c’ is the effective stress value of cohesion (very small)
’ is the effective stress (or drained) angle of friction.
’ n is the normal stress on the failure plane at failure.
Table 1 Typical values of drained angle of internal friction angles for sands and silts
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For sand and gravel, c’ = 0 (they are called cohesionless soil)
For normally consolidated and remolded clays, c’ = 0
For over consolidated clays, c’ = f (OCR)
Below the shear envelope - failure does not occur
At and above shear envelope - failure occurs
Inclination of Plane of Failure
Here, 1’ = Major principal stress
3’ = Minor principal stress
We can draw Mohr circle for the stress condition shown above as shown in the figure 3.
Figure 2 Stress systems in a soil mass
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Figure 3 : Failure envelope developed from the Mohr Circle
Let’s extend failure envelope to touch the x-axis at f.
Then, at a plane inclined at an angle of from major principal axis,
’ + 900 = 2
Therefore,2
450
From figure,
)
2
'45tan('2)
2
'45(tan'' 002
31
c
Here, c’ and ’ are the effective shear strength parameters.
For earth structures and soil-structure interaction (foundations) the Factor of
Safety against failure is given by:
ss to soil Shear stre
f soil Strength o FS
Determination of Shear Strength
Shear strength of soil can be measured in laboratory or in-situ.
Laboratory Measurement
There are different methods to measure shear strength of soil in laboratory.
a. Direct Shear Test
b. Triaxial Shear Test
c. Unconfined Compression Test
d. Simple Shear Test
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e. Ring shear device
Figure 4 : Sketch of an unconfined compression test device
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Unconfined Compression Test
ApplicationUnconfined compression test gives shear strength of soil. Shear strength is
important in all types of geotechnical designs and analyses.
EquipmentStrain controlled unconfined compression test device
Scale
Balance sensitive to 0.1 g
Moisture cans
Oven
Procedure
1. Get three trimmed soil specimens provided to you.
2. Measure the dimensions of the specimen (diameter and length).
3. Measure the weight of the specimen.
4. Load the samples into the unconfined compression device. They should be placed
in between two platens.5. Lower the upper platen slowly (or raise the lower platen depending upon the
machine), just to make contact with the top of the soil specimen.
6. Set the vertical displacement dial gauge and loading proving ring dial gauge to
zero.
7. Lower the upper platen (or raise the lower platen) at the speed of 0.5%/min.
8. Record the load and displacement dial gauge readings at every 5 or 10 seconds
depending on the type of the soil. Usually the readings are taken at every 0.01
inch of displacement.
9. The compression load goes on increasing, peaks, and then decreases.
10. After it starts to decrease, stop the test.
11. Reverse the platen movement, and remove the specimen.12. Draw a free hand sketch of the specimen after failure.
13. Determine the moisture content of the specimen.
14. Repeat this procedure for two more specimens.
Calculations
15. Calculate axial strain. = L
L
L = Vertical deformation of the specimen.
16. Calculate vertical load on the specimen.
Vertical load = Load cell reading x 1 Lb
17. Calculate the corrected area of the specimen (Ac)
1
0 A Ac
A0 = Initial cross-sectional area i.e. x D2/4
18. Calculate the stress on the specimen.
c A
Load
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19. Plot versus axial strain. Peak is qu. Then calculate su.2
uu
q s
Figure 5 Stress-strain curve and Mohr circle generated from UC Test
Table 2 Relationship between consistency and UC strength
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Soil Mechanics Laboratory
Unconfined Compression Test Laboratory Data Sheet
I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization:
Client: USUF Project: 324L
Boring no.: NA Recovery depth: NA
Recovery date: NA Recovery method: NA
Soil description:
II. TEST DETAILS
Initial specimen diameter, Do: Initial specimen area, Ao:
Initial specimen length, Lo: Initial specimen volume, V o:
Moist mass of specimen, M : Dry mass of specimen, M s:Moisture content, w: Total unit weight, : Dry unit weight, d :
Specimen preparation method: Hand Compaction
Deformation indicator type: Dial gauge Axial strain rate, 1/t :
Deformation dial gauge conversion factor, K L: x10-3 in
Force measurement instrument type: Load cell
Proving ring dial gauge conversion factor, K P : 1 lb
III. MEASUREMENTS AND CALCULATIONS
Deformation
Reading
(G L)
Axial
Deformation
( L)
Load
Reading
(G P )
Axial
Load
( P )
Axial
Strain
( 1)
Corrected
Area
( A)
Axial
Stress
( )
EQUATIONS:
1 = L/Lo
A = Ao/(1- 1)
1 = P / A
L = G L K L
P = G P K P
su = qu/2
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Unconfined compressive strength, qu:
Undrained shear strength, su:
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Soil Mechanics Laboratory
Unconfined Compression Test Laboratory Data Sheet
I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization:Client: USUF Project: 324L
Boring no.: NA Recovery depth: NA
Recovery date: NA Recovery method: NA
Soil description:
II. TEST DETAILS
Initial specimen diameter, Do: Initial specimen area, Ao:
Initial specimen length, Lo: Initial specimen volume, V o:
Moist mass of specimen, M : Dry mass of specimen, M s:
Moisture content, w: Total unit weight, : Dry unit weight, d :
Specimen preparation method: Hand CompactionDeformation indicator type: Dial gauge Axial strain rate, 1/t :
Deformation dial gauge conversion factor, K L: x10-3 in
Force measurement instrument type: Load cell
Proving ring dial gauge conversion factor, K P : 1 lb
III. MEASUREMENTS AND CALCULATIONS
Deformation
Reading
(G L)
Axial
Deformation
( L)
Load
Reading
(G P )
Axial
Load
( P )
Axial
Strain
( 1)
Corrected
Area
( A)
Axial
Stress
( )
Unconfined compressive strength, qu:
Undrained shear strength, su:
EQUATIONS:
1 = L/Lo
A = Ao/(1- 1)
1 = P / A
L = G L K L
P = G P K P
su = qu/2
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EGCE 324L (Soil Mechanics Laboratory)
Soil Mechanics Laboratory
Unconfined Compression Test Laboratory Data Sheet
I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization:Client: USUF Project: 324L
Boring no.: NA Recovery depth: NA
Recovery date: NA Recovery method: NA
Soil description:
II. TEST DETAILS
Initial specimen diameter, Do: Initial specimen area, Ao:
Initial specimen length, Lo: Initial specimen volume, V o:
Moist mass of specimen, M : Dry mass of specimen, M s:
Moisture content, w: Total unit weight, : Dry unit weight, d :
Specimen preparation method: Hand CompactionDeformation indicator type: Dial gauge Axial strain rate, 1/t :
Deformation dial gauge conversion factor, K L: x10-3 in
Force measurement instrument type: Load cell
Proving ring dial gauge conversion factor, K P : 1 lb
III. MEASUREMENTS AND CALCULATIONS
Deformation
Reading
(G L)
Axial
Deformation
( L)
Load
Reading
(G P )
Axial
Load
( P )
Axial
Strain
( 1)
Corrected
Area
( A)
Axial
Stress
( )
Unconfined compressive strength, qu:
Undrained shear strength, su:
EQUATIONS:
1 = L/Lo
A = Ao/(1- 1)
1 = P / A
L = G L K L
P = G P K P
su = qu/2
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UU Triaxial Test
Concept of Shear Strength
Please refer the same materials you got in Unconfined Compression test.
a. Triaxial Shear Test
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b. Triaxial test is more reliable because we can measure both drained and
undrained shear strength.
c. Generally 1.4” diameter (3” tall) or 2.8” diameter (6” tall) specimen is
used.
Figure 1 triaxial compression testing device
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d. Specimen is encased by a thin rubber membrane and set into a plastic
cylindrical chamber.
e. Cell pressure is applied in the chamber (which represents 3’) by
pressurizing the cell fluid (generally water).
f. Vertical stress is increased by loading the specimen (by raising theplaten in strain controlled test and by adding loads directly in stress
controlled test, but strain controlled test is more common) until shear
failure occurs. Total vertical stress, which is 1’ is equal to the sum of 3’
and deviator stress (d).
g. Measurement of d, axial deformation, pore pressure, and sample volume
change are recorded.
h. Depending on the nature of loading and drainage condition, triaxial tests
are conducted in three different ways.
i. UU Triaxial testii. CU Triaxial test
iii. CD Triaxial test
In this lab, we will conduct UU triaxial test.
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Unconsolidated Undrained Triaxial Test (UU Triaxial Test) As drainage is not permitted and consolidation is not necessary, this test is very
quick, and also referred as Q-test.
As drainage is not permitted, u increases right after the application of 3’ as well as
after the application of d.
As Uc = B. 3 and Ud = A . d
Total u = B. 3 + A . d
u = B. 3 + A . (1 - 3)
This test is common in clayey soils.
ApplicationUU triaxial test gives shear strength of soil at different confining stresses. Shear
strength is important in all types of geotechnical designs and analyses.
Equipment
Strain controlled triaxial load frame
Triaxial cell assembly
Cell pressure supply panel
Scale
Balance sensitive to 0.1 g
Moisture cans
Oven
Procedure (Follow the specific guideline provided in a separate sheet)
Measure diameter, length, and initial mass of the specimen.
Measure the thickness of the rubber membrane. Set a soil specimen in a triaxial chamber.
Increase the cell pressure to a desired value (70 kPa for the first case and 140 kPa
in the second case).
Shear the specimen at the rate of 1%/min or 0.7 mm/min (for 70 mm sample height).
In automated device, the software calculates it automatically based on the soil type.
Record L, and d in every 10 seconds (computer does it automatically).
Continue the test until the deviator stress shows ultimate value or 20% axial strain.
After completion of the test, release the cell pressure to 0, vent the pressure and
bring the cell down by bring the lower platen down, drain the cell, and clean theporous stone and the assembly.
Sketch the mode of failure.
Measure the weight of the soil specimen again, and put the specimen into the oven.
Measure the weight again after 24 hours.
Repeat the test for the second specimen too (140 kPa of cell pressure and third
specimen 210 kPa of cell pressure).
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Calculations
Calculate axial strain. = L
L
L = Vertical deformation of the specimen.
Calculate vertical load on the specimen.
You will get it directly from the force transducers.
Calculate corrected area of the specimen (Ac)
1
0 A Ac
A0 = Initial cross-sectional area i.e. x D2/4
Calculate the stress on the specimen.
c A
Load
Plot d versus axial strain separately for three tests. Plot d vs a for three tests in the same plot.
Plot Mohr circle based on 1 and 3 at failure. They should give the same d value.
Add one Mohr circle for unconfined compression test too (That you did last week).
Make a straight line, which is tangent to all Mohr’s circles. This gives cu with a
horizontal line, i.e. u = 0. Therefore this test is called = 0 test.
2
d uc
Calculate the moisture content of the specimen after the test.
Calculate the initial void ratio of the specimen (Use the equations provided in the
earlier classes).
Figure 2 Total stress Mohr circle and failure envelope obtained from UU triaxial test
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UU Triaxial Test Laboratory Data Sheet
I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization:Client: CSUF Project: Soils Lab
Boring no.: N/A Recovery depth: N/A
Recovery date: Recovery method: N/A
Soil description:
II. TEST DETAILS
Initial specimen diameter, Do: Initial specimen area, Ao:
Initial specimen length, Lo: Initial specimen volume, V o:
Moist mass of specimen after test, M : Dry mass of specimen, M s:
Moisture content, w: Total unit weight, :
Dry unit weight, d : Degree of saturation, S :Membrane type: Standard Rubber Membrane Axial strain rate, 1/t :
Deformation indicator: LVDT Force indicator: LVDT
Cell pressure, 3: Specimen preparation method: Hand Compaction
Notes, observations, and deviations from ASTM D2850 test standard:
III. MEASUREMENTS AND CALCULATIONS
Axial
Deformation
( L)
Axial
Load
( P )
Axial Strain
( 1)
Corrected
Area
( A)
Deviator
Stress
( )
EQUATIONS:
a = L/Lo
A = Ao/(1- a)
= P / A
1f = 3 + f
3:
f : 1f :
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I. GENERAL INFORMATION
Tested by: Date tested:
Lab partners/organization:
Client: CSUF Project: Soils Lab
Boring no.: N/A Recovery depth: N/ARecovery date: Recovery method: N/A
Soil description:
II. TEST DETAILS
Initial specimen diameter, Do: Initial specimen area, Ao:
Initial specimen length, Lo: Initial specimen volume, V o:
Moist mass of specimen after test, M : Dry mass of specimen, M s:
Moisture content, w: Total unit weight, :
Dry unit weight, d : Degree of saturation, S :
Membrane type: Standard Rubber Membrane Axial strain rate, 1/t :
Deformation indicator: LVDT Force indicator: LVDT
Cell pressure, 3: Specimen preparation method: Hand Compaction
Notes, observations, and deviations from ASTM D2850 test standard:
III. MEASUREMENTS AND CALCULATIONS
Axial
Deformation
( L)
Axial
Load
( P )
Axial Strain
( 1)
Corrected
Area
( A)
Deviator
Stress
( )
EQUATIONS:
a = L/Lo
A = Ao/(1- a)
= P / A
1f = 3 + f
3:
f :
1f :
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USER’S GUIDELINE FOR THE ELE TRIAXIAL DEVICE
(UU TRIAXIAL TEST)
POWER AND MAIN SUPPLY SETTINGS (This step is
already done)
1. Press the “Power Display” power button to the “ON” position. After Stabilization
(approx. 15 min.), push the “Tare” button to zero the display.
2. Turn on the laboratory vacuum supply. The associated amount of vacuum available to
your system will be displayed on the “Vacuum Supply Gauge”.
3. Turn on the laboratory compressed air supply. Viewing the “Pressure Supply” gauge,
adjust the “Master Regulator” until the desired maximum supply pressure is reached.
The displayed pressure should be about 10 psi more than the required cell pressure.
Do Not exceed 150 psi (1034 KPa) pressure.
4. Turn on the laboratory water supply.
FILLING OF THE DE-AIRED WATER TANK SYSTEM (This
step is already done)
1. Turn the “De-Airing Water Control” valve to the “Fill” position.
2. When the tank water level is about 1” from the top, turn the “De-Airing Water
Control” valve to the “vent” position (Very Slowly to allow water to drain).
DE-AIRING THE WATER TANK (This step is alreadydone)
1. Turn the “De-Airing Water Control” valve to the “Vacuum” position.
2. Apply vacuum for 10-15 minutes and, at the same time, gently shake the tank
occasionally to enhance the removal of air from water.
3. Turn the “De-Airing Water Control” valve to the “vent” position.
FILLING THE BURETTE CHANNELS (This step is already
done)
1. Set all five valves on the test cell to the closed position.
2. Set the “De-Airing Water Control” valve to the “Pressure” position.
3. Set the “Burette/Annulus Input Control” valve to the “vent” position.
4. Set the “Annulus Control Switch” to the “open” position (Normal).
5. Slowly turn the “Burette/Annulus Flow Control” valve to the “Fill” position. When the
water reaches the desired level, turn the “Burette/Annulus Flow Control” valve to
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the “Cell Operate” position. Do not overfill. Water should not be allowed to flow into
the pressure tube at the top.
6. Repeat the above steps until two burette channels being used are filled to the
desired level.
Note: If the water level in the “De-Aired Water Tank System” drops to about 1” from the
bottom, repeat the filling and de-airing procedures described above.
DE-AIRING THE BURETTE CHANNELS (This step is
already done)
1. Set the “Burette/Annulus Input Control” valve for each channel to the “vacuum”
position. Under normal operating conditions, the de-airing process should be
completed in about 5-10 minutes.
2. After completion, set all “Input Control” valves back to the “vent” position.
F PREPARATION OF THE SAMPLE
1. Trim the sample to be tested using a Miter Box.
2. Measure the height and diameter of the sample at various locations to get an
average value.
3. Measure the weight of the trimmed sample before test.
4. Wrap the sample in a plastic sheeting to prevent any moisture loss.
5. Use the trimmings to get the Moisture Content of the sample before test.
G PREPARATION FOR THE TRIAXIAL LOADING
1. Double click on the software icon “DS7” on the desktop.
2. Click on the button “New Test”.
3. Select “ UU1 --Triaxial Quick Undrained Tests-AS”.
4. Click on the button “Select a Machine for the Test”.
5. Fill in the spaces in this window and click on the button “OK” to the right side of the
screen. The fields marked * by their side can not be left blank and the characters
\ / * . , : ; @ # ~ ? can not be used while filling up the spaces.6. In the window “Tests in Progress” make sure that you select the test that you want
to run and then click on the button “OK” at the bottom of the screen.
7. Switch on the Load cell machine using the button at the back.
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H MONITORING THE TEST
1. In the “Test Monitoring” window, make sure that all the test data shown in the
upper left box is correct.
2. Click on the button “Start Test Stage” located to the upper right side of the screen. 3. In the next window select “Test Initialization” and click on button “OK” in the
bottom.
4. In the “Test Initialization” window, enter the previously measured sample Diameter,
weight, and height.
5. The bulk density of the sample will be calculated automatically by the software.
6. The information regarding the Membrane Thickness and Youngs Modulus are default
values and may not be changed, unless using a different kind of membrane around
the sample.
7. After entering all data click on the green button “Confirm Setup Data”.
8. This will bring you back to the “Test Monitoring” window.
9. Again click on button “Start Test Stage” located to the upper right side of thescreen.
10. This time select “Compression” from the menu and then click on button “OK” at the
bottom of the window.
I COMPRESSION STAGE
From the previous stage you will be directed to the screen titled “Compression
Stage for Undrained Test”.
1. Vent Cell Pressure Transducer to Atmosphere and Reset:
a. Set the “Burette/Annulus Input Control” valve to the “Pressure” Position.
b. Set the “Annulus Control Switch” valve to the “on” position.
c. Set the “Burette/Annulus Flow Control” valve to the “Cell Operate” position.
d. Make sure the cell pressure transducer is open to atmosphere and wait for
10 seconds.
e. In the DS-7 software window, click on the red button “Reset Cell Pressure”.
2. Fill and Pressurise Cell. Select Material Type and Press Button to Calculate
Suggested Rate of Strain on Enter Directly:
a. Close the valve on the test cell marked “CP”.
b. Carefully place the sample on the Triaxial cell base pedestal.
c. Place the top pressure pad and use black O-rings to secure the membrane
around the base pedestal and top pressure pad.
d. Place the Triaxial cell cover over the sample and use the three rods to
secure it in place.
e. Open the knob at the top of the glass cylinder and attach the tube marked
“CP” to the knob marked “water” located at the bottom left of the panel.
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Open the valve on the test cell marked “CP”. This will gradually fill the cell.
Control the flow using the valve marked CP.
f. Close the knob at the top of the glass cylinder when the cell is filled with
water.
g. Detach the tube marked “CP” from the knob marked “water” and attach it
back to the knob marked “CP” on the panel.
h. Close the valve on the test cell marked “CP”.
i. Use the knob in the “Set Pressure Control” panel to increase the pressure to
the desired cell pressure level. Monitor the cell pressure box in the DS-7
software to get the accurate reading.
j. Set the “Burette/Annulus Input Control” valve to “Pressure” position.
k. Slowly open the valve on the test cell marked “CP”. This will transfer the cell
pressure to the water inside the glass cylinder.
l. In the DS-7 software window, select the right “Material Type” to the right
side of the window and click on the button “Calculate Rate of Strain”.
m. Input the “calculated rate of displacement” value from the computer screen
to the display window at the bottom of the test cell and press Enter ().
3. Calculate Logger Sampling Rates (based on percentage of length of specimen at
failure):
a. On the DS-7 software window, fill up the boxes marked “first increments”,
“upto”, and “second increments”. This is the increment at which the results
will be captured by the transducers. The default values are from the ASTM
Standard. Set both for 0.01%.
4. Reset Force Transducer & Bring Piston just into contact with top cap:
a. Raise the sample using the key on the keypad on the loading frame until
the load piston just touches the top notch of the top plate above the soil
sample.
b. On the DS-7 software window, click on the red button marked “Reset Force
Transducer”.
c. This should reset the lower right window on the “Test Monitoring Window” in
the DS-7 software to 0.0 lbf.
5. Reset Axial Displacement & Start Compression at End of Count Down:
a. Place the “axial displacement transducer” bottom touching the horizontal rod
and click on the button “Reset Axial Displacement Transducer” on the DS-7
software window.
b. This should reset the lower left window on the “Test Monitoring” window of
the DS-7 software to 0.0 inches.
6. Click on the green “Continue” button at the bottom of the page of the software
window.
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7. A window will appear that will instruct you to press enter (Green Button) to start
the Test Countdown. If everything is ready, click on the green button “Start Test
Countdown”.
8. Once the two whistles go, press the green button “Run” on the keypad at the bottom
of the test cell.
J TO STOP THE TEST
1. To stop the loading at any time press the red button “Stop” on the keypad of the
load frame.
2. In the DS-7 software, on “Test Monitoring” window click on button “End Test Stage”
3. Click on button “Start Test Stage” button.
4. Select “Final Measurements” and click on OK.
5. Enter all parameters that are available at this time
Final Specimen Weight (wet)Final Specimen Weight (dry)
Initial Moisture Content from Trimmings
Lab Temperature during test
Particle Specific Gravity
6. Click on green button “Confirm Data”.
7. Click “OK” on the window stating “FINAL STAGE IS NOW COMPLETE. PRESS OK
TO STORE THE TEST DATA READY FOR ANALYSIS OR PRESS CANCEL TO
PERFORM FURTHER STAGES”.
8. Save the Raw data obtained from the test to a directory of your choice. The
software will prompt to a default directory.
9. Click on button “exit” to exit from the software.
K DRAINING THE CELL
1. Turn the “set Pressure Control” knob in counterclockwise direction to reduce the
cell pressure.
2. Turn the “Burette/Annulus Input Control” valve to “Bridge Off” position.
3. Open the top knob of the glass cylinder in the load cell assembly.
4. Set the “Burette/Annulus Flow control” to “drain” position.
5. Open the valve on the test cell marked “CP”. This will drain the water from the glass
cylinder.
L DISMANTLING THE CELL
Use the button on the keypad of the load frame to lower the sample away from
the load piston.
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Unscrew the three rods from the sides of the glass cylinder and take out the
cylinder.
Dismantle the sample from the test cell and secure the membrane, top and bottom
end plates.
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Stability Analysis of Slopes
Background
Evaluating the stability of slopes in soil is an important, interesting, and challengingaspect of civil engineering. Concerns with slope stability have driven some of the
most important advances in our understanding of the complex behavior. Extensive
engineering and research studies performed over the past 70 years provide sound
set of soil mechanics principles with which to attack practical problems of slope
stability. There are a number of methods ranging from very simple to highly
complicated numerical calculation approach, available for the stability analysis of
slopes and a number of computer software are available for the solution. However,
very simple methods that can be accomplished through a simple spreadsheet
programming are still popular. In this class, we will conduct stability analysis for a
slope for steady seepage condition using Ordinary Method of Slice and Bishop’s
simplified method and compare the results.
Simple theory involved in the analysis
Ordinary Method of slice
For the slope shown in the figure 1,
pn
n
nn
pn
n
nnn
s
W
CosW Lc
F
1
1
sin
)'tan'.(
(1)
Simplified Bishop’s Method
Based on the analysis made on the slope element shown in figure 2,
pn
n
nn
pn
n n
nn
s
W
mW Lc
F
1
1 )(
sin
1)'tan'.(
, where (2)
s
n
nn F
m
sin'.tancos)(
bn = width of the slice (We need to perform iteration for this analysis)
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Figure 1 Stability analysis by ordinary method of slices
Figure 2 Stability analysis by Bishop’s simplified method
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Stability Analysis for Steady-state Seepage
For steady-state seepage, we need to modify equations 1 and 2 to cover the influence of
water.
Equation (1) is modified as,
pn
n
nn
pn
n
nnnnn
s
W
LuCosW Lc
F
1
1
sin
)'tan)('.(
(3)
Equation (2) is modified as
pn
n
nn
pn
n n
nnnn
s
W
m LuW Lc
F
1
1 )(
sin
1)'tan)('.(
(4)
Information needed
Cross-section of slope
Engineering scale
Scientific calculator or computer
Procedure
1. Divide the entire slope into a number of equally spaced (or based on slopes)
slices.
2. Measure the required parameters and populate the excel spreadsheet (shown in
the table below).
3. Calculate factor of safety using the above equations. Compare with two methods.
Figure 3
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c w
slice X ys yw yg b hs hw hsave hwave W u Wcos Wsin L U WcosU
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
FS
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c w
slice X ys yw yg b hs hw hsave hwave W u Wsin L U WU m Num
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
FS
FS
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Slope A
Task:
1. Please calculate the factor of safety of slope A. Consider unit weight of soil as 18 kN/m3, cohesion as 2 kPa, and friction angle as 100.
2. Please also calculate the friction angle to give FS of 1 (Ignore cohesion).
3. Please design countermeasures to increase the factor of safety to 1.5. Examples of countermeasures are: head excavation, toe loading,
lowering ground water table, piling, and drilled shaft.
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EGCE 324L (Soil Mechanics Laboratory) Spring 2009
Instructor: Binod Tiwari, PhD
104
Example Problem
Calculate the factor of safety of this slope with both Bishop’s Simplified Method and
Method of Slice.
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EGCE 324L (Soil Mechanics Laboratory) Spring 2009
Instructor: Binod Tiwari, PhD
105
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EGCE 324L (Soil Mechanics Laboratory) Spring 2009Spring 2007
Instructor: Binod Tiwari, PhD
106
Method of Slice
18 c 0 43 w 10
slice X ys yw yg b hs hw hsave hwave W u Wcos Wsin L U WcosU
1 0 3.67 3.67 3.67 0.00 0.00
2 1.47 2.75 3.67 3.67 1.47 0.92 0.92 0.46 0.46 12.17 -32.04 4.60 10.32 -6.46 1.73 7.98 2.34
3 2.94 2.06 3.67 3.67 1.47 1.61 1.61 1.27 1.27 33.47 -25.14 12.65 30.30 -14.22 1.62 20.54 9.76
4 4.41 1.61 3.67 3.67 1.47 2.06 2.06 1.84 1.84 48.55 -17.02 18.35 46.43 -14.21 1.54 28.21 18.22
5 5.88 1.32 4.40 4.40 1.47 3.08 3.08 2.57 2.57 68.00 -11.16 25.70 66.72 -13.16 1.50 38.51 28.21
6 7.35 1.25 5.28 5.28 1.47 4.03 4.03 3.56 3.56 94.07 -2.73 35.55 93.96 -4.47 1.47 52.32 41.64
7 8.82 1.28 6.09 6.24 1.47 4.96 4.81 4.50 4.42 118.94 1.17 44.20 118.91 2.43 1.47 64.99 53.93
8 10.29 1.47 6.97 7.16 1.47 5.69 5.50 5.33 5.16 140.90 7.36 51.55 139.74 18.06 1.48 76.41 63.33
9 11.76 1.76 7.63 8.07 1.47 6.31 5.87 6.00 5.69 158.76 11.16 56.85 155.76 30.73 1.50 85.18 70.58
10 13.23 2.28 8.15 8.95 1.47 6.67 5.87 6.49 5.87 171.73 19.48 58.70 161.89 57.27 1.56 91.53 70.37
11 14.7 2.94 8.66 9.91 1.47 6.97 5.72 6.82 5.80 180.46 24.18 57.95 164.63 73.91 1.61 93.38 71.25
12 16.17 3.89 9.03 10.79 1.47 6.90 5.14 6.94 5.43 183.50 32.87 54.30 154.12 99.60 1.75 95.04 59.08
13 17.64 5.14 9.47 11.67 1.47 6.53 4.33 6.72 4.74 177.68 40.38 47.35 135.36 115.10 1.93 91.37 43.99
14 19.11 6.79 9.69 11.52 1.47 4.73 2.90 5.63 3.62 148.97 48.30 36.15 99.10 111.23 2.21 79.89 19.21
15 20.58 9.17 9.76 11.52 1.47 2.35 0.59 3.54 1.75 93.67 58.30 17.45 49.22 79.69 2.80 48.81 0.41
16 21.31 11.52 11.52 11.52 0.73 0.00 0.00 1.18 0.30 15.44 72.74 2.95 4.58 14.74 2.46 7.26 -2.68
550.24 26.63 549.62
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
FS 0.93
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Bishop’s Simplified Method
18 c 0 43 w 10
slice X ys yw yg b hs hw hsave hwave W u Wcos Wsin L U WU m Num
1 0 3.67 3.67 3.67 0.00 0.00
2 1.47 2.75 3.67 3.67 1.47 0.92 0.92 0.46 0.46 12.17 -32.04 4.60 10.32 -6.46 1.73 7.98 4.19 0.42 9.21
3 2.94 2.06 3.67 3.67 1.47 1.61 1.61 1.27 1.27 33.47 -25.14 12.65 30.30 -14.22 1.62 20.54 12.93 0.57 21.28
4 4.41 1.61 3.67 3.67 1.47 2.06 2.06 1.84 1.84 48.55 -17.02 18.35 46.43 -14.21 1.54 28.21 20.34 0.72 26.24
5 5.88 1.32 4.40 4.40 1.47 3.08 3.08 2.57 2.57 68.00 -11.16 25.70 66.72 -13.16 1.50 38.51 29.50 0.83 33.27
6 7.35 1.25 5.28 5.28 1.47 4.03 4.03 3.56 3.56 94.07 -2.73 35.55 93.96 -4.47 1.47 52.32 41.75 0.96 40.51
7 8.82 1.28 6.09 6.24 1.47 4.96 4.81 4.50 4.42 118.94 1.17 44.20 118.91 2.43 1.47 64.99 53.95 1.02 49.51
8 10.29 1.47 6.97 7.16 1.47 5.69 5.50 5.33 5.16 140.90 7.36 51.55 139.74 18.06 1.48 76.41 64.49 1.09 54.98
9 11.76 1.76 7.63 8.07 1.47 6.31 5.87 6.00 5.69 158.76 11.16 56.85 155.76 30.73 1.50 85.18 73.58 1.14 60.43
10 13.23 2.28 8.15 8.95 1.47 6.67 5.87 6.49 5.87 171.73 19.48 58.70 161.89 57.27 1.56 91.53 80.20 1.21 61.88
11 14.7 2.94 8.66 9.91 1.47 6.97 5.72 6.82 5.80 180.46 24.18 57.95 164.63 73.91 1.61 93.38 87.08 1.24 65.55
12 16.17 3.89 9.03 10.79 1.47 6.90 5.14 6.94 5.43 183.50 32.87 54.30 154.12 99.60 1.75 95.04 88.46 1.27 64.83
13 17.64 5.14 9.47 11.67 1.47 6.53 4.33 6.72 4.74 177.68 40.38 47.35 135.36 115.10 1.93 91.37 86.31 1.28 62.97
14 19.11 6.79 9.69 11.52 1.47 4.73 2.90 5.63 3.62 148.97 48.30 36.15 99.10 111.23 2.21 79.89 69.08 1.26 51.12
15 20.58 9.17 9.76 11.52 1.47 2.35 0.59 3.54 1.75 93.67 58.30 17.45 49.22 79.69 2.80 48.81 44.85 1.20 34.75
16 21.31 11.52 11.52 11.52 0.73 0.00 0.00 1.18 0.30 15.44 72.74 2.95 4.58 14.74 2.46 7.26 8.18 1.06 7.21
550.24 643.74
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
FS, trial 1.17
FS 1.17 5.88
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OW MUCH DID YOU LEARN?1. You are supposed to conduct a sieve analysis using the US # 10, #20, #50,
#100, and #200 sieves. What should be the order (sequence) of stacking of
those sieves from the top to the bottom?
a) #200, #100, #20, #50, #10b) #200, #100, #50, #20, #10
c) #10, #20, #50, #100, #200
d) #10, #50, #20, #100, #200
2. Uniformity coefficient of a sand specimen is 2. Out of the total mass, 10% mass
of the soil specimen were finer than 0.2 mm. Calculate the size of the soil
particle (D) in mm for 60% of the soil to be finer than D.
a) 0.4
b) 0.1c) 1.0
d) None of the above
3. Which of the following equipment are used for the measurement of the liquid
limit of soil using the Atterberg’s method?
a) Casagrande’s cup
b) Moisture can
c) Frosted glass plate
d) All of the above
e) (a) and (b)
4. While measuring the liquid limit of a soil specimen, what should be the maximum
size of the soil particle?
a) Particles passing the US #40 sieve
b) 0.425 mm
c) Particles passing through the US #200 sieve
d) (a) and (b)
5. When calculating the liquid limit of a soil specimen, number of cranks is plottedin x-axis and water content is plotted in y-axis. Liquid limit is the water contentfor 25 cranks. How do you plot that graph?
a) x-axis in log scale and y-axis in arithmetic scale
b) both axes in log scale
c) x-axis in arithmetic scale and y-axis in log scale
d) Both x- and y- axes in arithmetic scale
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6. While measuring the plastic limit of a specimen, the plastic limit is the moisture
content when soil thread crumbles at,
a) 25 cranks
b) 3.18 mm diameterc) 3.18 inch diameter
d) 20 cranks
7. The plasticity index of a soil is equal to,
a) liquid limit + plastic limit
b) liquid limit – plastic limit
c) plastic limit – liquid limit
d) water content – plastic limit
8.
While measuring the plastic limit of a soil, moisture contents of the specimenwere: 11.63%, 11.64%, 11.65%, and 51.42%. What should be the plastic limit of
the specimen?
a) 11.64%
b) 11.63%
c) 21.58%
d) I would repeat the test
9. For the soil classification system, USCS stands for,
a) Universal Soil Classification Systemb) Universal Soil Classification Service
c) Universal Soil Classification Standardd) Unified Soil Classification System
10. What does the symbol SC stand for in the USCS classification?
a) clayey sand
b) sandy clay
c) clayey siltd) silty clay
11. In a dam, difference between the head and tail water level is H. A square gridflow net is drawn to calculate the seepage discharge. Number of flow channels
was nf and number of equi-potential drops was nd. Coefficient of permeability ofsoil was K and hydraulic gradient was i. What should be the seepage discharge
per unit length of dam?
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a)d
f
n
n H K
b)d
f
n
ni K
c) f
d
nni K
d) f
d
n
n H K
12. A cofferdam was made in soil that has specific gravity of 2.7 and void ratio of
0.7. What is the critical hydraulic gradient for that soil?
a) 1.5
b) 0
c) 1
d) 2
13. What is the water content of the soil corresponding to the maximum Proctor
dry density, called?
a) liquid limit
b) maximum water content
c) optimum moisture content
d) shrinkage limit
14. What is the main difference between the Standard Proctor and Modified
Proctor tests?
a) Number of soil compaction layer in the Standard Proctor is 3,
whereas it is 5 in the Modified Proctor
b) Weight of the hammer in the Standard Proctor is approximately
double than that in the Modified Proctor.c) Drop height of the hammer in the Standard Proctor is 1.5 times less
than that in the modified Proctor
d) All of the above
e) (a) and (c)
15. Soil compaction is done to _____________________ .
a) increase the shear strength
b) increase the compressibility
c) increase the permeability
d) all of the above
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16. You are conducting a laboratory consolidation test on a 1 inch thick soil
specimen using both-side drainage. It took 24 hours to get 100% consolidation.
How long does it take for a 2 inch thick specimen to get 100% consolidation at
the same drainage condition?
a) 24 hoursb) 48 hours
c) 96 hoursd) 12 hours
17. There are two methods to estimate the coefficient of consolidation of soil in a
laboratory consolidation test. One method plots time in log scale in x-axis and
the other method plots the square root of time in x-axis. Using the square root
of time method, what do you directly calculate from the chart?
a)
t90 b) t100
c) t50 d) t10
18. Conducting a direct shear test, what do you directly measure?
a) c’ and ’
b) cu c) cu and u
d) V and H
19. A sand specimen was loaded in a direct shear device with a vertical load of 10 lb.
Maximum shear stress obtained at failure was 2.5 psi. The size of the shear box
was 2” x 2” and thickness of the specimen was 1”. What is the value of tan ’ ?
a) 4
b) 2
c) 1
d) None of the above
20. A soil specimen of 2” diameter was sheared in an unconfined compression device.Peak load at failure was measured as 31.4 lb. What is the value of the
unconfined compression strength?
a) 5 psi
b) 10 psic) 15.7 psi
d) 15.7 kN/m2
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21. An unconfined compression test gives _______________________.
a) drained shear strength
b) c’ and ’
c) undrained shear strengthd) (a) and (b)
22. What are the devices that we use in the unconfined compression test?
a) load frame to compress the specimen
b) triaxial cell
c) rubber membrane
d) all of the above
23. You are analyzing the stability of a dry slope made of sandy soil having drainedfriction angle of 450. Total of Wcos is 400 lb, and total of Wsin is 200 lb.
Total of the length of the slice is 50 ft. What is the value of the factor ofsafety of this slope, using method of slice?
a) 1
b) 2
c) 0.5
d) 1.5
24. You need to work as a geotechnical engineer to design slope stabilizing measures
(to improve the safety factor) for a landslide that has occurred recently. Whatmethod do you apply?
a. Reduce the load at the toe of the landslide
b. Drain the water outc. Increase the load at the head of the landslide
d. All of the above
25. You are conducting two UU triaxial tests for the identical specimens at the
confining stresses of 10 psi, and 30 psi. The deviator stress at failure for the
confining stress (3) of 10 psi was 20 psi. What should be the diameter ofMohr’s Circle for the confining stress of 30 psi?
a) 20 psib) 60 psi
c) 40 psid) 30 psi
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26. How do you measure the change in volume of specimen in a UU triaxial test?
a) by measuring the change in length of the specimen
b) by directly measuring the change in volume of water at the
burette.
c) by calculating the area of the specimen through the diameter ofthe specimen, multiplying it with the height of the specimen to
get the final volume and subtracting the final volume with theoriginal volume.
d) There is no volume change in a UU triaxial test.
27. In general, direct shear test is conducted to measure the,
a) drained shear strength
b)
undrained shear strengthc) unconfined shear strength
d) both (a) and (b)
28. Consolidation test is more important in case of,
a) clayey soil
b) sandy soil
c) filter materiald) none of the above
29. In a UU triaxial test, soil specimen is sealed in a rubber membrane and cellpressure is applied from outside in a radial direction. What is the objective of
sealing the specimen with rubber membrane?
a) To conduct the test in undrained conditionb) To maintain the difference between the cell pressure and pore
pressure so that the specimen can be confine at a certain effective
confining stress.
c) To make the sample more flexible
d) To maintain the same diameter of the specimen while shearing
30. The mass of a wet soil specimen in a tin was 240 g, the mass of the dry soil and
tin was 220 g. The mass of the tin was 20 g. What should be the nearest water
content?a) 9%
b) 10%c) 91%
d) 8%
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31. After a consolidation test, the water content of a soil specimen having specific
gravity of 2.7 was 20%. What should be the nearest void ratio?
a) 0.27
b) 0.43
c) 0.54d) 0.05
32. Which among the following is the nearest unit weight of water?
a) 9.8 lb/ft3
b) 9.8 kN/m3
c) 62.4 lb/ft3
d) (b) and (c)
33. Moist unit weight of a soil specimen after a Proctor compaction test was 20
kN/m
3
. Water content of the specimen was 25%. What should be the dry unitweight of that specimen?
a) 18 kN/m3 b) 16 kN/m3
c) 15 kN/m3
d) 24 kN/m3
34. The soil specimen retained in the pan of a standard sieve analysis test consists
of ____________________________.a) Sand
b) Silt
c) Clayd) (b) and (c)
35. D10 of a soil mass means ______________________________.
a) Diameter of the soil is 10 mm.b) 10% of the soil mass is finer than this size.
c) 10% of the soil mass is coarser than this size.
d) Average size of the particle.
36. Which among the following is the average size of the soil particle?
a) D10 b) D30
c) D50
d) D60
37. Liquid limit of a soil specimen is 83%. Plastic limit of that soil specimen is 43%.The soil specimen currently has 53% water content. Which among the following
is the current state of that soil?
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a) Liquid
b) Plastic
c) Semi-solid
d) Solid
38. Liquid limit of a soil specimen can be obtained from __________________.a) Rolling Method
b) Casagrande’s cup c) Hydrometer analysis
d) Sieve analysis.
39. While measuring the liquid limit, groove in the Casagrande’s cup method mustclose over a distance of approximately ______________________.
a) 12.5 mm
b) 10 mm
c)
25 mmd) 3 mm
40. Which among the following is the most general soil classification system?a) USCS
b) AASHTO
c) SW-CL
d) SW
41. On a graph of plasticity index versus liquid limit, what among the following is
true about the “A line”?
a) Soil above the A line is clay.
b) Soil above the A line is silt.c) Soil above the A line has high plasticity.
d) Soil above the A line has low plasticity.
42. A gravelly soil specimen has 6% clay and 2% silt. Uniformity coefficient is 5 andcoefficient of curvature is 0.8. What should be the USCS classification for that
soil?
a) GW-GC
b) GP-GC
c) GW-GM
d) GP
43. A Proctor compaction test is done to determine __________________.
a) Minimum dry density.b) Maximum dry density.
c) Optimum moisture content.d) (a) and (c)
e) (b) and (c)
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44. On a graph of maximum dry density versus water content for a Proctor
compaction test, which among the following is true?
a) Sand specimen always gives a bell shaped curved.
b) Optimum moisture content is the water content when the curve
intersects zero air void line.
c) Maximum dry density occurs at the peak of the curve.d) Zero air void line can be plotted without the Proctor compaction test
if the specific gravity of the soil is known.e) (c) and (d)
45. What among the following is true about the degree of saturation at maximum
dry density of soil in the Proctor compaction test?
a) S = 100%
b) S < 100%
c) S > 100%
d) S = 0%
46. What should be the value of degree of saturation at zero air void curve of
Proctor compaction test?a) 100%
b) < 100%
c) > 100%
d) 0 %
47. Pre-consolidation pressure of a soil mass can be determined by plotting a ___________.
a) Deformation – log time graph.
b) Deformation – time graph.
c) Void ratio (e) – log ’ graph.
d) (a) and (b)
48. A soil specimen needs 3 hours for 100% consolidation in a consolidometer having
both side drainage. How long does it take for 100% consolidation if it is drained
from one side only?
a) 3 hours
b) 45 minutes
c) 12 hours
d) 9 hours.
49. A dam was compacted at the void ratio of 0.7 with a uniform sand of specific
gravity of 2.7. The nearest critical hydraulic gradient for the dam is ______.
a) 1.5b) 0.5
c) 1.0
d) 2.0
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50. A square grid flow net for the seepage under a cofferdam shows 4 numbers of
flow lines and 12 numbers of equipotential lines. Difference between the
headwater and tail water was 10 m. Hydraulic conductivity of the material below
the cofferdam was 3 x 10-2 cm/s. The nearest seepage discharge per kilometer
length of dam should be ______________.a) 1 cm3/s
b) 1 m3/sc) 10-3 m3/s
d) 10-3 cm3/s
51. Strength of which among the following soils is most appropriately measured by
the unconfined compression testing device?
a) sandy soil
b) Over consolidated clay
c)
Gravelly soild) All of the above
52. An unconfined compression test is a ________________________.
a) special type of unconsolidated undrained test.
b) type of an undrained test.
c) type of u = 0 test.
d) All of the above
e) (a) and (b)
53. The deviator stress of failure for an unconfined compression test is 20 psi. The
nearest undrained shear strength is __________________________.a) 20 psi
b) 40 psic) 10 psi
d) 20 lb
54. An over consolidated clay having effective friction angle of 100 was sheared in
an unconfined compression device. What should be the nearest angle of
inclination of the failure plane in the specimen?
a) 350
b) 400
c) 450
d) 500
e) 550
55. A normally consolidated clay is sheared in a direct shear device of 4” x 4” size.The normal load was 320 lb. The peak shear resistance was 80 lb. What should
be the nearest value of cohesion?
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a) 4 psi
b) 5 psi
c) 0 psi
d) 4 kPa
56. Which among the following parameters are measured with a direct shear device?a) c’ and ’
b) c and c) , and u
d) (a) and (c)
57. A normally consolidated soil specimen has shown the following measurements
while sheared in a shear testing device.
= 50 psi u = 10 psi = 20 psi
The nearest value of tan is __________________.
a) 0.25
b) 0.5c) 2
d) 0.4
58. What is the major difference between the Bishop’s Simplified Method (BSM)and the Method of Slice (MS) for slope stability analysis?
a) BSM always gives higher safety factor value than the MS.b) BSM is an iterative method.
c) BSM considers the difference between the vertical inter-slice
forces into account.d) All of the above
e) (a) and (b)
59. A stability analysis was done for a sandy slope using the method of slice, and thefollowing information was obtained.
W cos – U = 1000 kN = 450
L = 200 m W Sin = 500 kN
What is the closest value of the factor of safety?
a) 1
b) 2c) 2.4
d) 1.2
60. A soil specimen is sheared in an unconfined compression test device and peak
deviator stress was determined to be 20 psi. What is the expected value of theundrained shear strength of that soil if the specimen is sheared at the same
condition in an UU triaxial device at the cell pressure of 30 psi?
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a) 50 psi
b) 10 psi
c) 20 psi
d) 5 psi
61. Volume of a soil specimen is 12 in3. This specimen is sheared in a UU triaxialtesting device. Change in length of the specimen is 1 in. If the initial area of the
specimen is 3 in2, what should be the nearest final volume of the specimen?a) 9 in3
b) 15 in3
c) 3 in3
d) 12 in3
62. An UU triaxial compression test was conducted to measure the shear strength
of soil for _____________________.
a)
slow and static loadingb) earthquake loading
c) soil layer sandwiched between two impermeable layersd) all of the above
e) (b) and (c)
63. How do we measure the volume change in the UU triaxial test?
a) By sealing the specimen in a rubber membrane and connecting the
ends of the specimen to the volume measuring device/burette withthe pipe.
b) By measuring the change in height of the specimen.
c) Volume change is not measured in UU triaxial test. Pore waterpressure is measured instead of it.
d) There is no need to measure the volume change, nor the pore waterpressure in the UU triaxial test.
64. Hydrometer analysis is done for soil classification in the following situation.
a) When soil is to be classified according to the USCS system
b) When soil is to be classified according to the AASHTO system
c) When % of clay is required
d) All of the above
e) a) and b)
65. Which among the following devices are used for specific gravity measurement?
a) Pycnometerb) Water bath
c) Thermometerd) a) and c)
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66. A constant head permeability test is done for…….
a) fine grained soil
b) coarse grained soil
c) both a) and b)
d) consolidation test
67. To measure hydraulic conductivity of a clay soil specimen, which among the
following tests do you perform?a) constant head permeability test
b) falling head permeability test
c) rubber balloon test
d) seepage analysis
68. For the same head difference, discharge of water from single walled cofferdam
is always.
a)
Half of that in the double walled cofferdamb) Between 1 – 2.0 times that in the double walled cofferdam.
c) Same as in the double walled cofferdamd) Double of that in the double walled cofferdam.
69. An equi-potential line is a line that has.
a) same hydraulic gradient
b) same discharge
c) same water contentd) none of the above
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Solution to Exercise Problems
QuestionNo. Answer
QuestionNo. Answer Question No. Answer
1 c 26 d 51 b
2 a 27 a 52 d
3 e 28 a 53 c
4 d 29 b 54 d
5 a 30 b 55 c
6 b 31 c 56 a
7 b 32 d 57 b
8 a 33 b 58 e
9 d 34 d 59 b
10 a 35 b 60 b
11 a 36 c 61 d
12 c 37 b 62 e
13 c 38 b 63 d
14 e 39 a 64 c
15 a 40 a 65 d
16 c 41 a 66 b
17 a 42 b 67 b
18 a 43 e 68 b
19 c 44 e 69 d
20 b 45 b21 c 46 a
22 a 47 c
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