engineering properties of soil.pdf
TRANSCRIPT
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Engineering Properties of soil
Assoc. Prof. Tirawat Boonyatee
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Soil and engineering construction
2
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As supporting material
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Bearing capacity (Strength) Settlement (Deformation)
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As sustained material
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Lateral pressures Lateral pressures & Settlement
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As transported material
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Weight, Volume / Compaction Stability of borehole wall
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As contaminated material
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Permeability Permeability
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Basic soil’s properties
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Physical PropertiesEngineering Properties
Chemical Properties
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Basic soil’s properties
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Physical PropertiesEngineering Properties
Chemical Properties
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9
VoidSolid
Soil as a group of particles
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Weight - Volume Relationships
10
Solid
Liquid
Gas Va
Vw
Vs
V
Vv
Ws
Ww
W
Volume of soil = V solid + V void = V solid + V air + V water = V s + V a + V w
Weight of soil = W solid + W liquid = W solid + W water
= W s + W w
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Volume relationships
→ Void ratio, Porosity, Degree of Saturation
Void ratio e =
Porosity n =
Degree of Saturation S = =
Solid
Liquid
Gas Va
Vw
Vs
V
Vv
Ws
Ww
W
v
s
V
V
vV
V
w
v
V
V 100%w
v
V
V
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Relationship between Void ratio and Porosity
e =
n =
11
v
v v
v s v
V V V nV
V V V V n
V
11
v
v v s
v s v
s
V
V V eV
V V V V eV
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13
Weight relationships→ Water content, Unit weight
Water content w =
Unit weight g =
Dry unit weight g d =
Solid
Liquid
Gas Va
Vw
Vs
V
Vv
Ws
Ww
W
w
s
W
W
(1 ) s v sW W W W w
V V V
sW
V g = g d (1+w)
g = r g
หนวยน หนัก
ควมหนแนน
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ควมถวงจเพะ (Specific gravity)
14
o
Unit weight of a given material
Unit weight of water (at 4 c) sG
G s of soil particle usually falls within
a range of 2.6 – 2.9
Mineral
Specific gravity
Quartz 2.65
Kaolinite 2.60
Illite 2.80
Montmorillonite
2.65 –
2.80
Halloysite 2.00 – 2.55
Potassium feldspar 2.57
Sodium feldspar 2.62 – 2.76
Hornblende
3.00 – 3.47
Limonite 3.60 – 4.00
Olivine 3.27 – 3.70
Soil G s
Gravel 2.65 – 2.68
Sand 2.65 – 2.68
Silty sand 2.67 – 2.70
Silt
2.65 –
2.68
Clay (inorganic) 2.68 – 2.70
Clay (organic) 2.62 – 2.66
Soils with mica orFe
2.75 – 3.00
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Apparent and Absolute G s
Apparent specific gravity
Volume of air included
Absolute specific gravity Volume of air excluded
Solid
Water
Air
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Relative density (Dr)
Indicate the in-situ denseness or looseness ofgranular soil
Dr =
Dr = relative density
e = in-situ void ratio of the soil
emax = void ratio in the loosest state
emin = void ratio in the densest state
18
max
max min
e e
e e
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D r and densities
by relation e =
D r =
1 s w
d
G g
g
( ) ( )
( ) ( ) ( ) ( )
1 1
1 1
s w s w
d min d d min d
s w s w
d min d max d min d max
G G
G G
g g
g g g g
g g
g g g g
( ) ( )
( )( )
d min d maxd r
d min d d max
Dg g g
g g g
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ASTM D-2049 : for gd(min) of granular soils
Mold volume = 0.1 ft3
(2,830 cm3)
Drop height = 1 inch
Mold
V m
= 0.1 ft3
Sand
1"
0.5"
20
s
d(min)m
W
=V g
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ASTM D-2049 : for gd(max) of granular soils
Mold volume = 0.1 ft3
(2,830 cm3)
Drop height = 1 inch
Vibrated table 2 lb/in2 surcharge at top of mold
vibrate frequency = 3600 rpm
vibrate amplitude = 0.025 in
vibrate time = 8 min
Mold
V m
= 0.1 ft3
Sand
1"
0.5"
21
sd(max)
m
W =
V g
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Qualitative Description of granular soil
The problem indetermining of Dr is due to
the difficulty to obtain the
undisturbed sample from
the field.
Granular soil
=>Cohesionless
Practically, Dr is
determined from
the N value of SPT (standard
penetration test)
the vertical effective stress
Gibbs and Holtz ‘s chart
Dr Designation
0~15 Very loose
15~50 Loose
50~70 Medium
70~85 Dense
85~100 Very dense
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Basic soil’s properties
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Physical PropertiesEngineering Properties
Chemical Properties
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Soil Particle Size Definitions
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Gravel
Sand
Silt
Clay
4.75 mm
75 m
5 m
โ
10 mm
100
m
10 m
1 mm
1 m
โ(Earth's crust)
(Rocks)
(Soils)
(Gravels)
ท(Sands)
ท(Silts)
(Clays)
(Granular Soils)
(Cohesive Soils)
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Soil Particle Size Definitions
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Name Size (mm) cobbles, boulders, rock fragment > 60
gravel: 4.75 - 60
sand: 0.075 – 4.75 silt: 0.005 - 0.075
Limit of unaided vision.
clay < 0.005
Limit of optical microscope resolution.
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Structure of coarse grained soil
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Angular Loosed state
Densed state
HoneycombRound
Subangular
Subround
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Structure of fine grained soil
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PacketFlocculatedDispersed
ตกตะกอนในน จด ตกตะกอนในน ทะเล
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Particle size analysis of soils
Determination of the size range of particles present in a soil Expressed as a percentage of total weight of dried soil
Composed of
Sieve analysis for large grain (>75m)
Hydrometer analysis for fine grain (< 75 m)
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Sieve analysis
Shaking the soil sample through a set of sieves that have
progressively smaller openings
Each successive lower sieve is approximately half of theopening of upper sieve
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O i ( )Si O i ( )Si
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Sieve no. and Opening
Sieve no 4=> 4 divisions in 1”
Opening ~ ¼ “
Sieve no 200
=> 200 divisions in 1”
Opening ~ 1/200 “
0.053270
0.075200
0.090170
0.106140
0.125120
0.150100
0.18080
0.21270
0.25060
0.35550
0.42540
0.50035
0.60030
0.71025
0.85020
1.0018
1.1816
1.4014
1.7012
2.0010
2.368
2.807
3.356
4.005
4.754
Opening (mm)Sieve no
0.053270
0.075200
0.090170
0.106140
0.125120
0.150100
0.18080
0.21270
0.25060
0.35550
0.42540
0.50035
0.60030
0.71025
0.85020
1.0018
1.1816
1.4014
1.7012
2.0010
2.368
2.807
3.356
4.005
4.754
Opening (mm)Sieve no
30
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Example
Percentage finer than size D2
4 3100%
1 2 3 4
weight below D2total weight
mp m m
mp m m m m
Size D1
Size D2
Size D3
Size D4
Pan
m1
m2
m3
m4
mp
mass retained on sieve SIEVES
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Example
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Hydrometer analysis
Analysis based on Stoke’s Law
Sediment velocity is proportional to diameter
The larger, the faster
As time lapse, concentration along depth varies
Indirect measure for percent finer of soil particles
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34 Hydrometer
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Schematic diagram of hydrometer test
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36 Grading curves
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Fuller packing
0.5
xat x
max
D% finer 100 D
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38 Important indexes
10
60
u
D
D C
D D
D C
6010
2
30c
B i il’ i
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Basic soil’s properties
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Physical PropertiesEngineering Properties
Chemical Properties
ท
C i f l
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40 Consistency of clays
Behavior of clays depends on amount of water
Addition of water reduce cohesion flow
Brittle solid Plastic Liquid
Plasticity: Property of a material that can be deformed rapidly withoutrupture, without elastic rebound, and without volume change
Cause of Plasticity: double-layer water
ff f d bl l l
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4
1
Effect of double-layer water to clay
A b ’ li i
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Atterberg’s limits
Water contents when the soils change their behavior
Atterberg’s limits
Shrinkage limit (SL) : No further volume change when moisture decreases
Plastic limit (PL) : Lower limit of that soils will exhibit plastic behavior
Liquid limit (LL) : Soils are about to flow when the moisture increases
Plasticity index = LL - PL
Li id li i (LL)
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Liquid limit (LL)
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Li id li it diti
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Liquid limit condition
Groove width 2 mm Water content, required to close a distance of 0.5
in along the bottom of groove after 25 blows
One blow generates shear stress of ~ 0.01 t/m2
At liquid limit, Shear strength of clay ~ 0.25 t/m2
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Fl
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Flow curve
Flow index
Fl i d
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Flow index
1
1
1 10 10 100
log
, or,
F
F
w w I N
N
I w w w w
tan
If [20,30]
; tan 0.121
25n
N
N LL w
Pl ti li it (PL)
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Plastic limit (PL)
Roll into 1/8” thread
Moist content at which soil crumbles
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Sh i k li it
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Shrinkage limit
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Shrinkage limit :Moisture content at which the volume of soil stop to change
C l l ti f Sh i k li it
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Calculation for Shrinkage limit
iSL w w
1 2
2
2
x 100 (%)
x 100 (%)
i
i f w
m mw m
V V w
m
r
PI d LI
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PI and LI
The amount of water that a soil can absorb during plastic state
The amount of water in natural state, normalize by PI
PI LL PL
w PL w PL LI
LL PL PI
PL LL
PI
LI = 0
LI = 1
Important of PI
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Important of PI
Indicate the strength of clay minerals in a soil The higher w it can hold, the stronger the plasticity it can exhibit
PI Type of clay
0
Nonplastic
1 - 5 Slightly plastic
5 - 10 Low plasticity
10 - 20 Medium plasticity
20 - 40 High plasticity
40++ Very high plasticity
53Meaning of Liquidity index
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53 Meaning of Liquidity index
Soils with LI > 1, when remolded will transformed toliquid phrase
Soil deposits that are heavily overconsolidated mayhave a LI < 0
Implicitly indicate the stress history of soil LI = 1 : Normally consolidated clay
LI = 0 : Over consolidated clay
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Activity (A)
Index that shows the influence of particle < 2 to the
plasticity index of soil
%
percent finer at 2
slope of PI -