soil mechanics book - internet

7/31/2019 Soil Mechanics Book - Internet

1/80

UNESCO-NIGERIA TECHNICAL &

VOCATIONAL EDUCATION

REVITALISATION PROJECT-PHASE II

YEAR I- SEMESTER

THEORY

Version 1: December 2008

NATIONAL DIPLOMA IN

BUILDING TECHNOLOGY

GEOLOGY/ SOIL MECHNICS

COURSE CODE: CEC 108


2/80

GEOLOGY / SOIL MECHNICS CEC 108

COURSE INDEX

WEEK 1. 1.0 SOIL MECHNICS AND GEOLOGY ----------------- 1

1.1Nature of Earth Crust ------------------------------------ 11.2Outer Zones of Earth ------------------------------------- 11.3The Crust and inner Zones of Earth -------------------- 21.4Minerals --------------------------------------------------- 21.5Physical Characteristic of Minerals ------------------- 31.6Rocks ------------------------------------------------------ 31.7Types of Rocks -------------------------------------------- 31.8Common Rock Forming Minerals ----------------------- 41.9Structure of Geology -------------------------------------- 51.10 Surface Processes ---------------------------------------- 61.11 Agent of Denudation ------------------------------------ 61.12 Types of Erosion ----------------------------------------- 71.13 Relevance of Engineering Geology to Civil Engineering

Structure --------------------------------------------------- 7

1.14 Surface Drainage and Ground Water Loweringi

( Dewatering ) in Soil ------------------------------------- 8


3/80

1.15 Surface Drainage ---------------------------------------- 91.16 Types of Drainage --------------------------------------- 9

WEEK 2. 2.0 GROUND OF WATER LOWERING ( DEWATERING )

2.1 Cofferdam --------------------------------------------------- 10

2.2 Grouting ----------------------------------------------------- 10

2.3 Well point ---------------------------------------------------- 11

2.4 Neutral and Refractive Stress ----------------------------- 11

2.5 Important of Drainage -------------------------------------- 12

2.6 Isostasy ------------------------------------------------------- 12

2.7 Earth Quake -------------------------------------------------- 12

2.8 Tectonic Movement of Earth Quake ---------------------- 13

2.9 Effect of Earth Quake --------------------------------------- 13

WEEK 3. 3.0 GEOLOGICAL MAPS ------------------------------------- 14

3.1 Applying Scale ---------------------------------------------15- 16

3.2 A Little History --------------------------------------------17- 18

WEEK 4. 4.0 DENUDATION --------------------------------------------- 19

4.1 Types of Weathering ----------------------------------------19

4.1.1 What Causes Weathering -------------------------------19

4.2 What Does Erosion Do ------------------------------------20ii

4.3 How Fast Does The Soil Form --------------------------20


4/80

WEEK 5. 5.0 GEOLOGICAL FACTORS AFFECTING THE

STABILITY OF THE SLOPES , CUTTING AND

EMBANKMENT ----------------------------------------------- 21 - 22

5.1 Faults ------------------------------------------------------ 23

5.2 What are Joints ------------------------------------------ 24

5.3 Dike --------------------------------------------------- 25- 26

5.4 Geothermal Reservoir ------------------------------- 27- 28

WEEK 6. 6.0 SOIL MECHANICS ------------------------------------ 29

6.1 Soil Profile ----------------------------------------------- 29

6.2 Engineering Definition of Soil ------------------------ 29

6.3 Shaft for Sewer Constructed by Freezing ------------- 30

6.4 Irrigation and Power -----------------------------------31- 32

6.4.1. Dams --------------------------------------------------31 - 32

WEEK 7. 7.0 DIFFERENT TYPES OF SOIL --------------------- 33 - 36

WEEK 8. 8.0 SOIL AGGREGATE ------------------------------------37

8.1 Porosity --------------------------------------------------- 37

8.2 Moisture Content ---------------------------------------- 38

WEEK 9. 9.0 SURFACE DRAINAGE AND WELLS -------------- 39

iii9.1 Drainage Pattern -------------------------------------- 40-45


5/80

WEEK 10. 10.0 GROUND WATER AND WELLS ----------------- 46 -48

10.1 Water Table -------------------------------------------- 49 - 53

WEEK 11. 11.0 USE OF SPRING AND PISTON ANALOGY TO

SUBSTANTIATE NEUTRAL AND EFFECTIVE

STRESSES ---------------------------------54 - 55

WEEK 12. 12.0 STRESS DISTRIBUTION IN SOIL DUE TO POINT

LOAD ------------------------------------ 56 - 57

12.1 Stress Distribution due to a Number of Point Loads ---58

WEEK 13. 13.0 CLAY SOIL ------------------------------------ 59 - 63

13.1 Mineralogical Study of Clay ------------------64 - 65

WEEK 14. 14.0 FORMATION OF TWO LAYER SOIL WITH TYPICAL

EXAMPLE LIKE KAOLINITE ------------------ 66

14.1 Clay Minerals ------------------------------------------ 67

WEEK 15 15.0 SOIL ------------------------------------------------- 68- 71

15.1 Relate Clay Mineralogy to Nigerian Soil --------- 72

15.2 Constituants of Soil ---------------------------73 - 74

iv


6/80

WEEK ONE ( 1 )1.0Soil Mechanics and Geology1.1 Nature of earth crust

Sourth AmericaOcean @ Crust

EquatorialIndenosia

CoreIndian ocean

Atlantic Ocean

The earth can be physically described as a ball of rock (crust or lithosphere) partly

covered by water (hydrosphere) and rapt in an envelop of air (atmosphere). To this (3)

physical zone, it is convenient to add biological zones (biosphere) which are in the outer

zones of earth.

1.2 OUTER ZONES OF EARTH

(1) THE ATMOSPHERE: - It is a layer of gases and vapour which envelopes the earth.

Geologically is important as the climate and weather.

(2) THE HYDROSPHERE:-These include all the natural water of the, ie oceans, seas,

lake, and river which cover about of the earth surfaces.

(3) BIOSPHERE: - This consists of great forest with countless swarms of animal and

insect.

(4) THE CRUST OR LITHOSPHERE: - Is the outer shell of the solid earth. It is made up

1


7/80

of rock in great variety on the land it up most layer is commonly a blanket of soil or other

deposit ie, desert sand.

1.3 The crust and inner zones of the earth

-- The diagram in fig 1 shows the equation section through the earth.

-- The deep interior is called the core which has metallic properties and a very high

density.

-- The surrounding zone of heavy rocks is known as the mantle or substratum up to a

boundary surface about which the rocks have physical properties which are different

which of mantle.

-- The dominant rocks occurring in the crust fall into two contrasted groups.

I) A group of light rocks granite and related types and sediment such as sand stones and

shakes formerly and assemblish with an average specific density of about 2.7.

ii) A group of dark and heavy rock consisting mainly of basalt related types with density

about 2.8 3.0 known as basic rocks.

The continent, them selves have a varied relief of plains, plateaus and mountain ranges,

the last rising to a maximum high of 29028 feet above sea level which is known as mount

eve rest.

1.4 MINERIALS

These are natural in organics substance having composition and regular structure to be

which its crystalline form is related.

2


8/80

1.5 PHYSICAL CHARACTERISTIIC OF MINERALS

Some element e.g gold, copper, sulphur and carbon (diamond and graphite) make

minerals by them selves but most minerals are compound of two or more elements.

Oxygen is by far the most abundant element in the rock, silicon is the most abundant

element after oxygen, not surprising that silicon should be the most abundant of all

oxygen in familiar as quartz a common mineral which is specifically characteristics of

granite, sandstone and quartz veins.

In the earities of mineral veins, quartz can be found as clear transparent prisms.

Diamond and graphite (coal) are both crystalline form of carbon for responding to the

contrasted physical properties one been hard and lorilliant the other soft opaque and

flaky. The crystals of diamond and graphite have very different lattice structure.

1.6 ROCK

These are molten magma the erupts from the heated region of the molten or cooling a

solidify to massive rock substance.

These are form as a result of volcanic activity which are generated in the molten or

exceptionally heated region or the crust it self. Naturally not all the magma reaches the

surface and the new rock formed in the crust by the consolidation of such magma are the

example of what are called intrusive rock.

1.7 TYPES OF ROCKS

The geologist distinguishes between three basic types of rock.

(1) Igneous Rock;- These were formed when molting magmas from interior of the earth

erupt and are forced to the surface, increasing the earth surface, the magma cooled down

3


9/80

to form a solid mass of crystal. The igneous rocks are therefore hard and massive.

Example of the rock is granite stone.

(2) Sedimentary Rock; - These are formed mainly by deposition under water in seas and

lakes. These are also formed by weathering and erosion or older mountain. Examples of

the rocks are chalk, lime stone, sand stone, and loose soil. Such as sand and gravel are

also described as sedimentary rocks.

Metamorphic Rock; - These are either igneous or sedimentary in origin whose

have

uttered as a result of intense pressure and physical change. Examples of the rocks

are slate, schist and gneiss.

1.8 Common Rock Forming Minerals

These take the form of chemical decomposition some or the entire mineral constituent of

the rock mass. For example carbon dioxide dissolve in water to form weak solution of

carbonic acid which will attack many of the carbon rock forming mineral or oxygen in

atmosphere and in rain will cause oxidation particularly of those rocks containing iron.

The among rock forming minerals, there chemical composition, there susceptibity to

chemical weathering and the principal soil product are as follow.

4


10/80

Chemicaldecomposition

Susceptibility tochemical weathering

Principal soilproduct

Quartz Silicon dioxide Highly resistance Gravel, Sand siltparticles

Orthoclase Aluminum silicate ofpotassium

Clay mineralproduct of kaoliniteand illate group

Plagioclase Aluminum silicate ofsodium of calcium

Moderatelysusceptibility

Clay mineralparticles of motorikiothite and

illite group

Mica Aluminum silicate ofpotassium,

magnesium and iron

Hornblende Silicate principallyof magnesium

Avgite

1.9 STRUCTURE OF GEOLOGY

Joint; - these are fracture along which particularly no displacement of the rock support.

These are common feature in granite rock formation.

Dip & Strike; - The dip include both direction of the maximum slope dawn a bending

plane and the angle between maximum slope and the horizontal.

5

Olivine Highly susceptible


11/80

The strike of an incline bend is the direction of any horizontal link along the bending

plane with still water ground.

Folds; - These occurs when bucking, bending and contortion of rocks by a group of

complex processes involving fracture, sliding sherry and flowage

Thrust; - This occur when the resulting fraction is in clinked at an angle between 45%

and the horizontal.

1.10 Surface processes

Denudation;- This is the processes which act the crust at or very near its surface, as a

result of the movements and chemical activities of air, water, ice and living organisms.

1.11 Agent of Denudation

1) Wind;- Blowing over lands the wind comes with its dust and sand.

2) Rain & River;- Shower of rain sinks into the soil and promote the work of decay by

solution and by loosing the particles.

3) Glaciers (moving ice);- Water expand on freezing and through repeated alternation of

frost and thaw in water filled pores and cracks the rock are relentlessly broken.

4) Animals and organism;- Life also co-operates in the work of destruction the roots of

trees grown down into the crack and assist in splitting up the rocks, warms and burrowing

animals bring up the finer particles of soil to the surface, where they fall a ready prey to

wind and rain.

The production of rock waste by these various agents, partly by mechanical breaking and

partly by solution and chemical decay is described as weathering.

6


12/80

Product Denudation;- Sands, dusts, rocks, minerals substance i.e. Tin, Diamond, coal etc.

Winds, river and glaciers, the agent that carry the product of rock waste are

known as transporting agent.

The destructive processes are due to the effects of the transporting agent are described as

erosion.

1.12 Types of Erosion

1) Rain Erosion;- The effect of rain water contribute to soil removal, but where the soil

has a strong cover of vegetation and particularly if it firmly bounds together by a mat of

interlacing grass roots it is well protected against rapid surface erosion.

2) Gully Erosion;- This is formed by large deep trench at the slope-end of hill side due to

high run-off result of high rainfall.

3) River Erosion;- This leads to hydraulic lifting and scouring cavitations.

4) Glacier Erosion;- this is limited to sub-glacier streams.

5) Wind Erosion;- Slowing off a fine sand.

6) Marine Erosion;- The effect of sea and ocean wave, tides and current.

1.13 RRELEVANCE OF ENGINEERING GEOLOGY TO CIVILENGINEERING STRUCTURE

These are carried out to select the best location for a project site and to aid in

formulating the preliminary design or the structure .i.e. Dam project, uniting e.t.c.

(1)Investigation;- This involve surface and deep surface investigation to collect rock( 2) sample, soil sample, inspection of rock curt and other excavations location of

construction materials.

7


13/80

An important example is the construction of dam, reservoirs in which the following

information are needed for safety design.

(i) To ascertain bed of in fragmented rock base formation.

(ii) Remove of any pervious material within the dam length which might case failure .i.e.

(iii) Minimize sea page in soil by constructing curt off well.

(vi) Clay are normally used as materials for construction of a dams because of its relative

low rate of permeability.

In the case of tunnel construction, drilling of bore holes, are carried out which will reveal

various information as follows.

(1) Measurement of fracture and joint fomentation in rocks.

(2) Rock names and description of various engineering properties .i.e. attraction laying

and other geologic effects.

(3) Location and amount of water and gas in flow.

(4) Geological seismic method may be used to define the thickness of loosened rock

around the tunnel. This can also be used on the ground surface to define the approximate

depth of bed rock or various rock-layers.

1.14 SURFACE DRAINAGE AND GROUND WATER LOWERING(DEWATERING) IN SOIL

Depending on the modern of construction and their function drains can be classified as

surface and sub surface types, surface drains are usually shallow and are effective in

8


14/80

disposing the surface run-off (storm or inigation).

Subsurface drains are depth and usually meant for the under drainage of infiltrating

water. The technique for dealing with the problem those results is depending on the

occupation dimensions the soil types and the ground water control requirements.

1.15 SURFACE DRAINAGE

For an effective drainage system to be carried the following investigation are needed.

(1) Topography; - The topography of the area will indicate the ridge and valley lines and

the direction of the natural surface run-off.

(2) The soil; - soil characteristics are vital to any form of drainage to be designed.

(2)Ground water information; - This will enable the designer to known the waterlogging

(3)areas and point of high water table.1.16 TYPES OF DRAINAGE

(1) Storm or inigation run-off follows the natural valley lines which can be easily found

the contour map of the areas.

(2) Open drains;-

These types of open drains are constructed at the side of road embankments.

(3) Close drains; - This consist of open-jointed pipes made of ultrified clay a of concrete.

9


15/80

WEEK TWO ( 2 )

2.0 GROUND WATER LOWERING (DEWTEARING

The following method are used to lower the ground water (dewater) on sites.

(1) Caissons method; - This involve excavation form within the permanent impervious

structures. The structure is either built in place if the site in an land or floated into

position if the site is in water the structure or partial structure is in position, excavation

form within begins. As excavation proceeds the structure sinks due to its own weight, that

may be added, and the process is continued until final foundation elevation is reached.

2.1 COFFERDAMS; - These are structure build in place to exclude water and earthfrom

an excavation. In those instances where the distance across the excavation is sufficiently

small to permit internal bracing, single-walled coffer dam construction is used. These are

normally used for bridge pier foundations.

Slurry French method; - The method involves construction an imperious bonier beneath

the ground surface. As excavation for the wall is progressing, the material removed: the

slurry is sufficient to support the excavation walls. When the excavation has been

competed concrete placement proceeds by the tremor method from the button to the top

of the excavation the slurry displaced by this by this operation is collected for reuse.

When the concrete has ared. The construction site is enclosed within a rigid impervious

barrier.

2.2 Grouting; - These are used in permanent work to construction offs for ground waterand

sometimes have been employed as construction aids in dewatering. The processes involve

10


16/80

injection of chemical or cement grounds into the voids of pervious soil when these

ground solidify, they form an impervious barrier. The success of the operation will

depend on the distribution of the ground injection.

Open sumps; - This is sample and cheap are can be carried onto with very planning. It is

well suited to some situation .i.e. types of soils; in cohesive soil supping method work

best these are soils that are nearly impervious.

The procedure above illustrates the button of an excavation area which is graded to drain

to a central location where pumps are installed.

Cohesion less soil; - are usually of sufficiently high permeability that the success of a

supping operation will depend on the acceptability of comparatively large pumped

capacities and certain problem that may arise from movement of soil particle to the

sumps.

2.3 Well point; - A well point dewatering system consist of a series of closed spacedsmall-

diameter well drain to shallow depts. These wells are connected to a pipe or header that

the excavation and that is attached to a vacuum pump.

2.4 NEUTRAL AND RFFRCTIVE STRESS

At any horizontal section dept Z in a soil profile, the total douched pressure is due to the

weight. Soil above the section.Resistance to this pressure is provided, partly be the soil

grains (which is the effective stress) and if the section is below the water table partly by

the upward pressure of the water, which is the neutral stress or pure water pressure.


17/80

112.5 IMPORTANT OF DRAINAGE

(1) To prevent water logged area.

(2) This on able construction activities to be carried out with ease.

(3) To prevent destruction of structure .i.e. roads, buildings etc.

(4) Effective use of the land area.

2.6 ISOSTASY

When a mountain range is cured into peaks and valleys and gradually worm down by the

agents of denudation, reduced by the weight of the rock-waste that has been carried away.

At the same time a neighboring column under laying a region of delta and sea floor where

the rocks waste is being deposited receive a correspond in crease of load, unless a

compensating transfer of material occurs in depth, the two columns can be remain in

isostalic equilibrium. At the base of the crust the pressure exerted by the banded column

is increase, while that exerted by the un banded column is decrease. In response to this

pressure difference in the mantle a slow migration of material in set going which leads to

the loaded column to sick and the un banded column to rise. This process is referred to as

isostalic readjustment.

2.7 EARTH QUAKE

When a stone is thrown into pool of water, a series of waves spreads through the water in

all directions similarly when rocks are suddenly disturbed, vibration. Spread out in all

direction of the source of the disturbance. There fore an earthquake is the passage of

these vibrations. Those are set up in solid bodies by the scraping together of two rough

blow or rupture surface. Corresponding cause of earth quake in the earth is crust volcanic


18/80

12explosion, the initiation of faults and the movement of rock along fault planes.

2.8 Tectonic movement of earth quake

Is the building up of stresses in rock until they are strained to breaking point, when they

suddenly rupture and more generally along fault.

2.9 Effect of earth quake

One of the most alarming features of a great earthquake experienced on land near the

place of origin to the passage of ground land waves which are thrown the surface in to

ever changing undulation which lead to destruction of:

(a) Structure builds across a fault.

(b) Water pipes and gas pipes are cracked open as well as road.

(c) Railways are buckled and twisted bridge collapse and building crash to the ground.

(d) Glaciers are shattered and where they terminate and break off in the sea ice beings

because unusually abundant.

(e) Ground water its circulation may be greatly disturbed in other ways by earthquakes.

(f) Loss of human life as a result of collapse of building in highly populated areas.

Continental Drift and ocean .

13


19/80

WEEK THREE ( 3 )

3.0 Geological maps

Topographic Map

In addition to showing general locations and political boundaries, topographic maps depict the geology and

special features of an area. This type of map offers many advantages. For instance, most backpackers use

topographic maps to navigate through wilderness, planning their routes with obstacles and landmarks in

mind. If they should get lost, they can find their bearings again by aligning their map and compass to a

prominent feature observed nearby. A key on each map indicates the distance scales and special symbols

(for features such as railroads, schools, airstrips and water towers) used to create it. Generally, the green

on a topographic map indicates forest or vegetation, while the white areas indicate areas that are bare of

growth. Series of brown lines indicate mountains and hills, showing elevation and relative steepness. Each

line represents a specific unit of elevation; where the lines are very close together, the terrain is quite

steep.

14


20/80

3.I. Applying a scale

Example: Bernard wants to make a plan of his bedroom; it is rectangular and is 5 m long

and 2.50 m wide.

He decides to divide the real dimensions by 20:

5 m = 500 cm and 500 cm 20 = 25 cm; 2.5 m = 250 cm and 250 20 = 12.5 cm.

So he draws a rectangle with a length of 25 cm and a width of 12.5 cm.

This rectangle is a plan of his room to the scale of .

Note: The dimensions of the plan are the real dimensions multiplied by the scale factor of

; in fact: and ;

the dimensions of the plan are proportional to the real dimensions; the scale factor is

.Definition: On a map (or a plan), the dimensions are equal to the real dimensions

multiplied by the same numbere. The numbere is called the map scale.

IfD is a real distance that is represented on the map by a distance d, then

D e = d(the distances must be expressed in the same unit).

II. Calculating a scale

Example 1: What is the scale e of the architectural plan mentioned in the introduction

(12 meters represented by 48 centimeters)?

So:D = 12 m = 1,200 cm and d= 48 cm.

So: 1,200 e = 48, or (simplifying by 48).

The scale of the plan is equal to .

Note: ; we can also say that the scale factor is equal to 0.04, but it is usual, where15


21/80

possible, to write the scale as a fraction with a numerator of 1 when the scale is less than1.

Example 2: On a road map, a straight road 1 kilometer (km) long is represented by 1 cm.

What is the scale of this map?

So:D = 1 km = 100,000 cm and d= 1 cm. We can call the scale of the map e.

So: 100,000 e = 1, or .

The scale of the map is equal to .

Example 3: Using a microscope, you photograph a paramecium that is 0.2 millimeters

(mm) long. On the photograph, the paramecium is 10 cm long. What is the scale of this

photograph?

So:D = 10 cm = 100 mm and d= 0.2 mm. We can call the scale of the photograph e.

So: 0.2 e = 100, ore = 100 0.2 = 500.

The scale of the photograph is equal to 500.

Note: In this example, the photograph is an enlargement; this is because the scale is

greater than 1.

III Using a scale

A. Example 1: calculating a real distance

Look again at the second example given in the introduction. What is the distance that

Peter must cover (the distance represented by 5 cm on a map with a scale of ?

We apply the formulaD e = d, with and d= 5 cm.

So: , orD = 5 25,000 = 125,000.Therefore D = 125,000 cm = 1.25 km.Peter must cover 1.25 km.

B. Example 2: calculating a reduced length

16


22/80

On the same map, how is a path 750 m long represented?

We apply the formulaD e = d, with and D = 750 m.

So: , therefore d = 0.03 m = 3 cm.

On the map with a scale of , a path 750 m long is represented by 3 cm.

I. What is a scale?

A. Examples and definition

On a map drawn to the scale of , the distances are 10,000,000 times smaller than thereal distances.

To draw it, the real distances are multiplied by , which is the same as dividing themby 10,000,000.In the same way, on a reproduction of an insect to the scale of 15, the insect isrepresented 15 times larger than in reality. To draw it, the real dimensions of the insectare multiplied by 15.Definition: The scale of a reproduction is the number by which the real dimensions aremultiplied.Note:A scale factor is always a positive number;the scaled measurements are proportional to the measurements in reality;usually, a reducing scale is written as a fraction, but it does not have to be; so the scale

can also be written in decimal format as 0.0000001.

3.2 . A little history

The first map of the whole kingdom of France was created at the request of Louis XV,who was impressed by the mapmaking carried out in Flanders. Csar-Franois Cassini deThury, also known as Cassini III, was asked to complete this map on a scale of 1/86,400.The map was based on the grid network created between 1683 and 1744 by his father andgrandfather.The survey began in 1760 and was completed by his son Jacques Dominique Cassini in

1789. The publication of the maps was delayed by the French Revolution and was notcompleted until 1815. Four generations of Cassinis were devoted to the creation of thismap, which was used as a reference by the cartographers of the principal Europeannations throughout the first half of the 19th century.

II. How is a scale used?

17


23/80

A. If the scale is given by a number

Go back to the example of the map created to the scale of .To draw this, the real distancesfor example the distance from Paris to Rome as the

crow fliesare all multiplied by the same number, here .The distance between Paris and Rome as the crow flies is around 1,200 kilometers (km).The two towns are therefore 0.00012 km apart on the map (since1,200 0.0000001 = 0.00012). This distance is expressed in kilometers, which is not avery convenient unit to use for a map; converting it into centimeters, it is 12 cm.In the case of the reproduction of an insect, the real dimensions (for example, the lengthof a leg) are all multiplied by the same number: 15. A leg that actually measures 5millimeters (mm) will measure 75 mm on the drawing, that is, 7.5 cm (15 5 = 75).

B. If the scale is given by a comparison of two lengths

For some maps and plans, the scale is given like this: 1 cm to 25 km, or 1 cm to 350meters (m), etc.In the first case, 25 km on the ground is represented by 1 cm on the map. So, if somethingmeasures 10 cm on the map, the distance on the ground will be 250 km (10 25 = 250).In general, ifn is a positive number, a distance ofn cm on the map represents a realdistance of 25 n km on the ground.

18


24/80

WEEK FOUR ( 4 )

4.0 Denudation;

Leaving the parched grassland of white-owned farms, we crossed into the

homelandand total denudation. Most of the cattle had starved long ago; even the land's

few goats were gaunt. I stopped at Thoma, a dusty village of thatch-roofed rondavels and

empty cattle kraals, and talked with Mphephu Shibambu, mother of five.

4.1 Types of weathering;

Most soils begin to form when big rocks break up. The breaking up of rocks is called

weathering. Weathering makes pieces of rock smaller and smaller. There are two kinds of

weathering, physical weathering and chemical weathering. After weathering breaks up

rocks, a process called erosion spreads the broken bits about.

4.1.1.WHAT CAUSES WEATHERING?

Most physical weathering is caused by ice. Ice is frozen water, and water expands when it

freezes. Freezing water makes a powerful force. When water seeps into cracks in rocks

and freezes, it can split the rock apart. Strong winds and growing tree roots can also break

up rocks.

Water causes most chemical weathering. Chemical weathering changes the materials that

make up rocks. Rain pours down on rocks, rivers flow over rocks, and waves pound rocks

along beaches. The water takes certain minerals out of rocks. For example, grains of sand

19


25/80

form after water takes a mineral called feldspar out of granite rock.

4.2 WHAT DOES EROSION DO?

Erosion also makes soil. Erosion can help break up rocks, but it mainly moves weathered

rock. Water, wind, and glaciers cause erosion. Wind or water can wear away rock on a

hillside. Water moves the eroded rock down the hill. Wind blows dust away. Glaciers are

big sheets of ice that move over land. The moving ice grinds up and carries the rocks

below it.

4.3 HOW FAST DOES SOIL FORM?

Most soils form very slowly. It can take as long as a million years for weathering to break

down some rocks.

Chemical weathering works faster in warm, wet climates than in cool, dry climates. Also,

plant and animal parts decay and make humus faster. Soils that form in warm, wet

climates are usually better for growing plants. Physical weathering is the main type of

weathering in cool, dry climates.

Most soils begin to form when big rocks break up. The breaking up of rocks is called

weathering. Weathering makes pieces of rock smaller and smaller. There are two kinds of

weathering, physical weathering and chemical weathering. After weathering breaks up

rocks, a process called erosion spreads the broken bits about.

20


26/80

WEEK FIVE ( 5 )

5.0 Geological Factors affecting the stability of slopes cutting and

embankment.

Although nonscientists were distressed at the inability of geologists and volcanologists to

predict these events, forecasting eruptions of stratospheric volcanoes like Mount St.

Helens is quite different from forecasting eruptions of midocean shield volcanoes, like

Kilauea on the island of Hawaii. The latter type produce a very hot and highly fluid lava,

whose path to the surface can be monitored by the measurement of earthquake activity

and ground tilting, that is, changes in the slope of the ground caused by the penetration of

molten rock from below. In volcanoes like Mount St. Helens, a sluggish, thicker lava,

moving slowly toward the surface, plugs the throat of the volcano and effectively bottles

up all the gases from below, until the resulting pressure is released in an explosion

The Caribbean coast and eastern mountain slopes generally receive twice as much annual

Pacific slope is due to the presence of cold stable air caused by the cold California

Current. This current, much like the Peru, or Humboldt, Current along the Peruvian coast,

chills the air, thus preventing it from absorbing much water vapor and reducing the

possibilities for precipitation. In contrast, the effects of the warm water of the Caribbean

Sea allow the air to absorb abundant moisture, which is then carried by the prevailing

easterly winds. Much condensation and rainfall occur as the winds flow up and over the

21


27/80

high slopes of Central America. Rainfall is greatest along the Mosquito Coast of

easternmost NicaraguaSan Juan del Norte receives about 6,350 mm (about 250 in) of

rain per year.

Sledding Down a Snowy Slope

Three friends enjoy a sled ride down a snowy slope in the

Austrian Alps. The Alps are home to many winter resorts.

22


28/80

5.1 Faults;

Plates that slide past each other make breaks in the crust called faults. The edges of

sliding plates can get stuck together. The plates keep trying to move, and pressure builds

up. Suddenly, the plates break free. Plates that move suddenly can cause an earthquake.

The ground shakes. Earthquakes can damage houses and other buildings.

San Andreas Fault23


29/80

Where Earths tectonic plates collide, great cracks called

faults are formed. The San Andreas Fault in California

marks where the North American and Pacific plates come

together.

5.2 WHAT ARE JOINTS?

Joints are the places where two or more bones meet. Most bones are tied together at joints

by tough bands called ligaments.

Different kinds of joints let you move in different ways. Move your lower arm up and

down. Keep your upper arm still. The joint that joins your upper and lower arm is called

the elbow. Your elbow works like a hinge. It lets you move your lower arm, but only up

and down. Now swing your arm all around from your shoulder. A joint in your shoulder

called a ball-and-socket joint lets you move your arm in many directions.

Your skull is made of many bones that do not move. They are held together in one solid

piece by suture joints.

24


30/80

5.3 Dike (geology), in geology, wall-like intrusion of igneous rock, cutting acrossother strata

of preexisting rocks, originally formed by a flow of molten rock into a fissure in which it

cooled and solidified. A dike may range from a few centimeters to thousands of meters

thick and from a few meters to many kilometers long. Frequently the rock material of the

dike is harder than the surrounding rocks, and as a result it may be left standing by itself

after the neighboring rock has weathered away. Similar intrusions of igneous rock that lie

parallel to the enclosing layers are known as sills.

Levee, embankment along the course of a river. Natural levees are low banks that are

produced by the river during floods when the overflowing of the river decreases the speed

of the water and permits the deposit of silt. Artificial levees are considerably higher than

natural ones and protect the surrounding countryside from floods. Levees are, in general,

similar to the protective dikes in the Netherlands that prevent flooding by the sea.

On a large river such as the Mississippi, floods cannot be controlled by levees alone

because the waters rise to heights that would overwhelm any embankment. Levees are,

however, used to protect portions of the riverbank areas, such as cities and towns, that

have a high economic value. The floodwaters are allowed to flow through breaks in the

25


31/80

levees over land of low value and are drained off through supplementary channels that

are sometimes equipped with secondary levees

Kariba Dam

The Kariba Dam lies along the border between Zambia and Zimbabwe. The facility controls flooding and

supplies hydroelectric power to both countries. A public road traces the rim of the dam, between reservoir

Lake Kariba and the drop to the Zambezi River. The distinct arch shape distributes pressure evenly on the

overall structure of the dam.

26


32/80

5.4 Geothermal reservoir;

In certain areas, water seeping down through cracks and fissures in the crust comes in

contact with this hot rock and is heated to high temperatures. Some of this heated water

circulates back to the surface and appears as hot springs and geysers. However, the rising

hot water may remain underground in areas of permeable hot rock, forming geothermal

reservoirs. Geothermal reservoirs, which may reach temperatures of more than 350 C

(700 F), can provide a powerful source of energy

Geothermal Energy Plant

27


33/80

Geothermal energy plants generate electricity and heat by harnessing the heat energy contained within

the earth. The earth transfers its energy to deep-lying circulating water, which the plants access with wells

28


34/80

WEEK SIX ( 6 )

6.0 SOIL MECHANICS

Soil mechanics is basically concerned with the behavour of performance of soils

as they relate to design of construction.

6.1 SOIL PROFILE

G.L

Top soil laterally 500mm

Hard part

The eng Sub soilIs concern G. W. L.

With thisPortion. SOIL

( eng. Soil )

BED - ROCK

6.2 ENGINEERING DEFINATION OF SOIL

For engineering purposes, soil is considered to any loose sedimentary deposit , such as

gravel , sand , silt , clay, or amixture of these materials . It should not be confused with

geological definition of soil , which is the weathered organic material on the surface or

topsoil. Topsoil is generally removed before any engineering projects are carried out.

29


35/80

Civil engineering is perhaps the broadest of the engineering fields, for it deals with the

creation, improvement, and protection of the communal environment, providing facilities

for living, industry and transportation, including large buildings, roads, bridges, canals,

railroad lines, airports, water-supply systems, dams, irrigation, harbors, docks, aqueducts,

tunnels, and other engineered constructions. The civil engineer must have a thorough

knowledge of all types of surveying, of the properties and mechanics of construction

materials, the mechanics of structures and soils, and of hydraulics and fluid mechanics.

Among the important subdivisions of the field are construction engineering, irrigation

engineering, transportation engineering, soils and foundation engineering, geodetic

engineering, hydraulic engineering, and coastal and ocean engineering

SOIL MECHANICS

6.3 Shaft for Sewer Constructed by Freezing.

In New York, contractors used freezing to dig a shaft for a sewer tunnel under the East

River. The tunnel is part of the collecting system which takes New York sewage to a

treatment plant in Brooklyn. The tunnel was bored through bedrock 225 ft. under the

river. The 26-ft. diameter shaft, however, extended through water-bearing ground for the

first 125 ft. of depth. The contractor chose to freeze the ground around the excavation by

driving a ring of 21 pipes to surround the work, and then circulating brine through them.

Two 125-hp. refrigerating plants were connected to the tops of the pipes. After several

weeks of continuous freezing, a solid wall of frozen wet ground dammed off the flow of

water. Excavation of the shaft was carried out inside the frozen ring by usual excavating

30


36/80

methods. As excavation proceeded, the shaft was lined with 3 ft. of reinforced concrete.

Ground Subsidence at Long Beach.

Officials of Long Beach, Calif., took steps to halt subsidence of the ground over Terminal

Island's 20-sq. mi. oil field. Since 1936, when the first oil well was drilled, over 800

million bbl. of oil have been pumped out of the oil-bearing strata. In 1941 surface sinking

was first noticed, and since then it has reached a total of over 20 ft. The major concern is

at the center of the area, where the Navy's $175 million shipyard and drydock, and the

Southern California Edison Co.'s steam generating plant are located. The $60 million

crash program, designed only to halt the subsidence, calls for injecting one million bbl. of

salt water a day through 260 water wells drilled into the strata, which lie at depths from

2,000 ft. to 6,000 ft. The injection of salt water is expected to greatly increase oil

recovery.

6.4 IRRIGATION AND POWER

6.4.1. Dams.

Hebgen Dam Withstands Earthquake.

Hebgen Dam, a 44-year-old earthfill power dam on the Madison River, west of

Yellowstone Park, was in the news in August. An earthquake of 7.8 intensity (the 1906

earthquake in San Francisco measured 8.2) rocked the region, wrecked paved highways,

caused landslides, killed a dozen people, and caused the water in the reservoir to slosh

over the top of the dam. Investigation after the quake showed an open crack in the

concrete core wall, but no leakage of water through the dam itself.

Aswan Dam.

31


37/80

The Egyptian High Dam Authority announced that Russian equipment began to arrive in

Egypt for first-stage construction of the new Aswan Dam on the Nile River. An

Egyptian-Soviet contract for $17 million started the construction, with Soviet engineers

supervising. The designs for first-and second-stage construction are being made by a

London firm of engineers.

32


38/80

WEEK SEVEN ( 7 )

7.0 Different types of soil

As yet there is no worldwide, unified classification scheme for soil. Since the birth of the

modern discipline of soil science roughly 100 years ago, scientists in different countries

have used many systems to organize the various types of soils into groups. For much of

the 20th century in the United States, for example, soil scientists at the USDA used a

classification scheme patterned after an earlier Russian method. This system recognized

some three dozen Great Soil Groups.

In 1975 a new classification scheme known as soil taxonomy was published in the United

States and is now used by the USDA. Unlike earlier systems, which organized soils

according to various soil formation factors, the new system emphasizes characteristics

that can be precisely measured, including diagnostic horizons (which give clues to soil

formation), soil moisture, and soil temperature. In a manner similar to the kingdom,

phylum, class, order, family, genus, species system used to classify living things, the

USDA soil taxonomy employs six categories. From the general to the more specific, its

categories are order, suborder, great group, subgroup, family, and series. This system has

classified more than 17,000 types of soil in the United States.

Sand is an important constituent of most soils and is extremely abundant as a surface

deposit along the courses of rivers, on the shores of lakes and the sea, and in arid regions

33


39/80

(see Soil; see Soil Management). One specific form of sand is the major ingredient inglassmaking. Other types of sand are used in foundries to make casting molds and in

ceramics, plasters, and cements. Sand is used as a grinding and polishing abrasive in the

form of sandpaper, which is a sheet of paper covered on one side with sand or a similar

abrasive substance. Sandblasting is an important technique used for cleaning stone or for

smoothing rough metal surfaces by blowing a stream of sand under air or steam pressure.

Desert on Atlantic Coast

The Namib Desert, primarily in Namibia, Africa, stretches alongside the Atlantic Coast in Africa for 1,930

km (1,200 mi).

34


40/80

Gobi Desert

The Gobi Desert in northeastern China is a windswept, nearly treeless wasteland. The Gobi ranks as the

coldest, northernmost desert in the world and covers more than 1,300,000 sq km (500,000 sq mi). The

terrain consists mostly of dry, rocky, sandy soil. Only 5 percent of the desert is covered with sand dunes.

Photo Researchers, Inc.

Sandstone, coarse-grained, sedimentary rock consisting of consolidated masses of sand

deposited by moving water or by wind. The chemical constitution of sandstone is the

same as that of sand; the rock is thus composed essentially of quartz. The cementing

material that binds together the grains of sand is usually composed of silica, calcium

carbonate, or iron oxide. The color of the rock is often determined largely by the

cementing material, iron oxides causing a red or reddish-brown sandstone, and the other

materials producing white, yellowish, or grayish sandstone. When sandstone breaks, the

cement is fractured and the individual grains remain whole, thus giving the surfaces a

granular appearance. Sandstones of various geologic ages and of commercial importance

35


41/80

are widely distributed in the U.S. Besides serving as a natural reservoir for deposits of oil

and gas, sandstone is used in building flagstone pavings and in the manufacture of

whetstones and grindstones.

Sandstone

Sandstone is a type of sedimentary rock made from accumulated particles of sand. The particles are

deposited by water, galciers, or wind and are eventually compressed and cemeted together to make

sandstone. Sandstone comes in a variety of colors.

36


42/80

WEEK EIGHT ( 8 )

8.0 SOIL AGGREGATE

Individual soil particles tend to be bound together into larger units referred to as

aggregates or soil peds. Aggregation occurs as a result of complex chemical forces acting

on small soil components or when organisms and organic matter in soil act as glue

binding particles together.

Soil aggregates form soil structure, defined by the shape, size, and strength of the

aggregates. There are three main soil shapes: platelike, in which the aggregates are flat

and mostly horizontal; prismlike, meaning greater in vertical than in horizontal

dimension; and blocklike, roughly equal in horizontal and vertical dimensions and either

angular or rounded. Soil peds range in size from very fineless than 1 mm (0.04 in)to

very coarsegreater than 10 mm (0.4 in). The measure of strength or grade refers to the

stability of the structural unit and is ranked as weak, moderate, or strong. Very young or

sandy soils may have no discernible structure.

8.1 POROSITY

The part of the soil that is not solid is made up of pores of various sizes and shapes

sometimes small and separate, sometimes consisting of continuous tubes. Soil scientists

refer to the size, number, and arrangement of these pores as the soil's porosity. Porosity

greatly affects water movement and gas exchange. Well-aggregated soils have numerous

pores, which are important for organisms that live in the soil and require water and

oxygen to survive. The transport of nutrients and contaminants will also be affected by

37


43/80

soil structure and porosity

8.2 MOISTURE CONTENT

Water occurs as moisture in the upper portion of the soil profile, in which it is held by

capillary action to the particles of soil. In this state, it is called bound water and has

different characteristics from free waterSee Soil; Soil Management. Under the influence

of gravity, water accumulates in rock interstices beneath the surface of the earth as a vast

groundwater reservoir supplying wells and springs and sustaining the flow of some

streams during periods of drought.

On striking the surface of the earth, the water follows two paths. In amounts determined

by the intensity of the rain and the porosity, permeability, thickness, and previous

moisture content of the soil, one part of the water, termed surface runoff, flows directly

into rills and streams and thence into oceans or landlocked bodies of water; the remainder

infiltrates into the soil. A part of the infiltrated water becomes soil moisture, which may

be evaporated directly or may move upward through the roots of vegetation to be

transpired from leaves. The portion of the water that overcomes the forces of cohesion

and adhesion in the soil profile percolates downward, accumulating in the so-called zone

of saturation to form the groundwater reservoir, the surface of which is known as the

water table. Under natural conditions, the water table rises intermittently in response to

replenishment, or recharge, and then declines as a result of continuous drainage into

natural outlets such as springs. See Spring.

. 38


44/80

WEEK NINE ( 9 )

9.0 SURFACE DRAINAGE AND WELLS

Drainage (geology), means by which water in an area drains, or flows away, in streams

and rivers and by seeping through the ground. A drainage system consists of all the

bodies of water, including rivers, lakes and groundwater (water under the ground),

through which water flows. The water in drainage systems originates as rain or as snow

that subsequently melts. Most rain does not fall directly into river channels or lakes.

Instead, it falls on land, and much of this rain percolates into the ground. From there,

most of it flows through the upper soil layers and soon emerges and enters small streams.

Scientists study drainage patterns and drainage systems in an attempt to analyze the

environmental impact of human activities and natural processes on these systems. Human

activities, such as damming rivers, draining wetlands for development, and altering

drainage patterns for agriculture or forestry use, may upset the balance of nutrients,

plants, and animals in the ecosystem. Natural processes, such as erosion (the removal of

rock and soil material), and deposition (the depositing of rock and soil material), may

also be altered by

39


45/80

Stream Capture

Over time, a stream on the steep side of a mountain slope will erode the slope faster than a stream on the

less steep slope, and may erode the drainage divide that separates them. When the fast-eroding stream

erodes a notch in the drainage divide, it eventually takes over the headwaters of the slow-eroding stream

on the other side and captures it.

9.1 DRAINAGE PATTERN

A drainage pattern describes the characteristic way tributaries, or streams that feed other

larger streams, and rivers branch off in different directions. Drainage patterns assume

many different forms, depending largely on the geological structure of the rocks on which

they form. The most common drainage pattern is called dendritic. A dendritic drainage

pattern tends to develop where a whole drainage basin is made up of the same type of

rock. Dendritic drainage resembles the shape of a tree, with the smallest tributaries being

the outermost twigs and the main river channel forming the trunk. In a dendritic drainage

pattern, tributary streams generally join at an acute, or less than 90 degree, angle, forming

Y-shaped junctions. 40


46/80

A rectangular drainage pattern is made of numerous cracks that form a grid pattern. This

pattern is common over certain types of rock, such as granite, in which cracks called

joints develop to form a grid. Stream channels tend to follow these joint systems.

Radial drainage patterns occur where rivers flow in all directions away from a raised

feature. The raised feature may be a volcano or a mass of rock that is more resistant to

erosion than the surrounding rock and therefore stands high. Centripetal drainage is found

where rivers flow from surrounding high ground toward a central basin, which is often

occupied by a lake.

Drainage Patterns

Streams tend to form five different kinds of drainage patterns: dendritic, rectangular, radial, centripetaland trellis. The patterns result from the type of soil in the area of drainage and the erosion of the soil by

flowing water. Dendritic, branching patterns form in areas of flat sedimentary rock, while areas with high

central peaks, such as volcanoes, exhibit radial drainage patterns. Sometimes, water flows into a bowl-

shaped valley by centripetal drainage and creates a lake, or erodes areas between ridges to create deep

valleys, as seen in trellis drainage.

41


47/80

Spring (water), natural flow of water from the ground at a single point within a restricted

area; when a spring has no visible current, it is called a seep. Springs may emerge at

different points on dry land or in the beds of streams, ponds, or lakes. Cold spring waters

are usually of meteorological character, that is, rain that has soaked into the ground and

emerged as a spring at some other point on a lower level. Hot spring waters may be of

igneous origin, or they may represent surface waters heated by contact with underground

uncooled igneous rock, as the hot springs and geysers at Yellowstone National Park. See

Geyser.

Classified according to their modes of origin, there are gravity springs, or those not

confined by impervious beds, and artesian springs, in which the water is under pressure

because it is confined to a pervious bed or a fissure (see Artesian Well). Grouped

according to the nature of the water-conducting passages, springs are of three types: (1)

seepage, in which the water seeps out from sand and gravel; (2) tubular, or those formed

by tubular passages in glacial drift or easily soluble rocks; and (3) fissure, in which the

water issues along bedding, joints, faults, or cleavage planes. Pollution is likely where the

water flows, for some distance, in an underground channel way of somewhat open

character.

The composition of spring water varies with the character of the surrounding soil or

rocks. Volume of flow of any given spring may vary with the season and amount of

rainfall. Seepage springs often fail in periods of drought or little rainfall. Nevertheless,

some springs have a fairly constant and even large volume of flow and may serve as

sources of domestic or municipal water supply (see Water Supply and Waterworks).

42


48/80

Some springs are also of medicinal value because of the dissolved mineral substances

they contain (see Mineral Water; Water)

Mineral Springs

Jinan is well known for the many local natural springs that provide it with pure water. Although often

hailed as the city's main attraction, some of these springs have been adversely affected by increased

industrial and domestic demands for water. As the capital of Shandong province on the Huang He, Jinan

has developed into a major transportation and industrial center. Despite major industrialization and

development in recent years, this ancient city retains many relics of historical importance. The

surrounding area is highly regarded for its natural beauty.

Corbis

As the atmosphere warms, the surface layer of the ocean warms as well, expanding in

volume and thus raising sea level. The melting of glaciers and ice sheets, especially

43


49/80

around Greenland, further swells the sea. Sea level rose 10 to 25 cm (4 to 10 in) during

the 20th century. (The range is due to measurement uncertainties and regional variation.)

By the end of the 21st century, sea level is projected to rise another 28 to 58 cm (11 to 23

in) if greenhouse gas emissions continue to increase significantly. The projection is

somewhat lessa rise of 19 to 37 cm (8 to 15 in)for a scenario in which greenhouse

gas emissions peak around the year 2050 and then decrease. These projections do not

incorporate possible large-scale melting of the Greenland or Antarctic ice sheets, which

could begin in the 21st century with warming of a few degrees Celsius.

Rising sea level will complicate life in many island and coastal regions. Storm surges, in

which winds locally pile up water and raise the sea, will become more frequent and

damaging. Erosion of cliffs, beaches, and dunes will increase. As the sea invades the

mouths of rivers, flooding from runoff will also increase upstream.

44


50/80

Low-Lying Island Nation

The government of Maldives, a low-lying island nation in the Indian Ocean, has expressed concern over

rising sea level attributed to global warming. Most of the land of Maldives sits only 2 m (6.5 ft) above sea

level, and even a modest rise could threaten the nations existence. Maldives has a larger population than

some other island nations, such as Tuvalu and Kiribati, which are already experiencing saltwater intrusion

due to rising sea level.

. 45


51/80

WEEK TEN ( 10 )10.0 GROUND WATER AND WELL

Groundwater, water found below the surface of the land. Such water exists in pores

between sedimentary particles and in the fissures of more solid rocks. In arctic regions,

groundwater may be frozen. In general such water maintains a fairly even temperature

very close to the mean annual temperature of the area. Very deep-lying groundwater can

remain undisturbed for thousands or millions of years. Most groundwater lies at

shallower depths, however, and plays a slow but steady part in the hydrologic cycle.

Worldwide, groundwater accounts for about one-third of one percent of the earth's water,

or about 20 times more than the total of surface waters on continents and islands.

Groundwater is of major importance to civilization, because it is the largest reserve of

drinkable water in regions where humans can live. Groundwater may appear at the

surface in the form of springs, or it may be tapped by wells. During dry periods it can

also sustain the flow of surface water, and even where the latter is readily available,

groundwater is often preferable because it tends to be less contaminated by wastes and

organisms.

The rate of movement of groundwater depends on the type of subsurface rock materials

in a given area. Saturated permeable layers capable of providing a usable supply of water

are known as aquifers. Typically, they consist of sands, gravels, limestones, or basalts.

Layers that tend to slow down groundwater flow, such as clays, shales, glacial tills, and

silts, are instead called aquitards. Impermeable rocks are known as aquicludes, or

46


52/80

basement rocks. In permeable zones, the upper surface of the zone of water saturation is

called the water table. When heavily populated or highly irrigated arid areas withdraw

water from the ground at too rapid a rate, the water table in such areas may drop so

drastically that it cannot be reached, even by very deep wells.

Although groundwater is less contaminated than surface waters, pollution of this major

water supply has become an increasing concern in industrialized nations. In the United

States, many thousands of wells have been closed in the late 20th century because of

contamination by various toxic substances.

Tapping Water Sources

Water is vital to humans. It is needed for food preparation, drinking, washing, and irrigation. In addition,

47


53/80

massive quantities are used daily in industrial processes. Yet, it is a limited resource that must be

collected and distributed with increasing care. The most important source of water is rain, which may be

collected directly in cisterns and reservoirs or indirectly through a watershed system or well. A watershed

is the network of rivulets, streams, and rivers by which entire areas are watered. Ground water is rain

that has trickled through rock layers, forming pools after many years. If it is under pressure, groundwater

may bubble to the surface as a spring. Irrigation canals, reservoirs, wells, and water towers are man-

made devices for diverting and collecting water from these natural sources. Because of contamination

concerns, water from reservoirs, wells, and rivers is usually processed in a treatment plant before

distribution.

Soil scientists also characterize soils according to how effectively they retain and

transport water. Once water enters the soil from rain or irrigation, gravity comes into

play, causing water to trickle downward. Water is also taken up in great quantities by the

roots of plants: Plants use anywhere from 200 to 1,000 kg (440 to 2,200 lb) of water in

the formation of 1 kg (2.2 lb) of dry matter. Soils differ in their capacity to retain

moisture against the pull exerted by gravity and by plant roots. Coarse soils, such as those

consisting of mostly of sand, tend to hold less water than do soils with finer textures, such

as those with a greater proportion of clays.

Water also moves through soil pores independently of gravity. This movement can occur

via capillary action, in which water molecules move because they are more attracted to

the pore walls than to one another. Such movement tends to occur from wetter to drier

areas of the soil. The movement from soil to plant roots can also depend on how tightly

water molecules are bound to soil particles. The attraction of water molecules to each

48


54/80

other is an example of cohesion. The attraction of water molecules to other materials,

such as soil or plant roots, is a type of adhesion. These effects, which determine the so-

called matric potential of the soil, depend largely on the size and arrangement of the soil

particles. Another factor that can affect water movement is referred to as the osmotic

potential. The osmotic potential hinges on the amount of dissolved salts in the soil. Soils

high in soluble salt tend to reduce uptake of water by plant roots and seeds. The sum of

the matric and osmotic potentials is called the total water potential.

In soil, water carries out the essential function of bringing mineral nutrients to plants. But

the balance between water and air in the soil can be delicate. An overabundance of water

will saturate the soil and fill pore spaces needed for the transport of oxygen. The resulting

oxygen deficiency can kill plants. Fertile soils permit an exchange between plants and the

atmosphere, as oxygen diffuses into the soil and is used by roots for respiration. In turn,

the resulting carbon dioxide diffuses through pore spaces and returns to the atmosphere.

This exchange is most efficient in soils with a high degree of porosity. For farmers,

gardeners, landscapers, and others with a professional interest in soil health, the process

of aerationmaking holes in the soil surface to permit the exchange of airis a crucial

activity. The burrowing of earthworms and other soil inhabitants provides a natural and

beneficial form of aeration.

10.1 WATERTABLE

Water Table, underground border between the ground in which all spaces are filled with

water and the ground above in which the spaces contain some air. The level of the water

49


55/80

table tends to follow the shape of the overlying ground surface, rising under hills and

dipping in valleys, but with a gentler slope than the ground. The level of the water table

also varies with the climate, rising during rainy periods and falling during dry spells.

Wells dug down to below the water table will fill with water. Such wells provide 20

percent of the drinking water used in the United States today.

The water table forms when rainwater seeps into the soil or bedrock instead of

evaporating back to the atmosphere or flowing directly into a stream as surface runoff.

Most soils and many rocks are both porous and permeable. Porous materials have

openings, such as cracks, voids, and spaces between particles, that can contain water.

These openings are called pores. Permeable materials are materials that allow water to

flow through them. At shallow depths, the pores are filled with a mixture of air and

water. This region constitutes thezone of aeration, orunsaturated zone. Water

percolating downward eventually fills all available pore space below a certain level,

forming the saturated zone. The surface, or border, between the zone of aeration and the

saturated zone is the water table. Surface tension can cause water to rise a short distance

from the water table. This produces a transition zone between the saturated and

unsaturated zone called a capillary fringe (see Capillary Action).

Water in the saturated zone is referred to as groundwater. Some soils and sedimentary

rocks are so porous that water can occupy up to 40 percent of their volume. As depth

increases, high pressures squeeze the pores shut. As a result, almost all groundwater is

found in the top 8 km (5 mi) of the earths crust. Groundwater contains about one-third of

1 percent of the earths water, or about 20 times more than the total found in rivers and

50


56/80

lakes. (The oceans account for 97 percent of the earths water.)

An aquiferis a body of rock or soil that is sufficiently porous and permeable to store and

transfer significant amounts of groundwater. An aquiclude is a body of relatively

impermeable rock. An aquifer is called confined when it is bounded above and below by

aquicludes or unconfined when there is no aquiclude above it. A perched aquifer is a

body of groundwater that lies above the regional water table because it is underlain by a

small aquiclude. The top of this small zone of saturation is known as a perched water

table.

Water flows in and out of aquifers as part of the water cycle. The flow of water into

aquifers is called recharge and the flow of water out of aquifers is called discharge. The

places where recharge occurs are called recharge areas. Discharge occurs wherever the

ground dips down to the level of the water table. For example, springs occur in valleys

where the valley sides meet the water table. If an enclosed depression in the earth dips

below the water table, water can flow out of the saturated zone and into the depression,

forming a lake or pond.

When recharge is equal to discharge, the water table is stationary. Heavy rainfall or

spring melt can cause recharge to temporarily exceed discharge and the water table will

rise. A rising water table may produce temporary springs, streams, and ponds. These

temporary discharge areas then drain water from the aquifer and lead to a restoration of

the original level of the water table.

If a well is dug down below the level of the water table, it will start to fill with water. As

51


57/80

water is removed from the well, the water table surrounding the well will drop, forming a

cone-shaped depression in the water table. The depth and steepness of the cone of

depression depend on how fast the water is being withdrawn, how porous and permeable

the aquifer is, and how fast the aquifer is being recharged. If the water table drops below

the bottom of a well, the well will run dry. Many of the major aquifers throughout the

world are being drained faster than they recharge. If this trend continues, many wells will

run dry.

Withdrawing groundwater faster than it can be recharged can also lead to subsidence, or

sinking, of the land. Parts of the Imperial Valley in California have subsided more than 8

m (26 ft) and New Orleans, Louisiana, and Houston, Texas, have each subsided by about

2 m (about 7 ft) due to groundwater withdrawal. Subsidence is irreversible. Once the land

has settled and collapsed its pore space, the space is no longer available to hold

groundwater. Subsidence is a special concern in coastal areas that could sink below sea

level.

Any human activity that reduces recharge contributes to the lowering of the water table.

For example, the construction of impermeable surfaces, such as roads, parking lots, and

buildings, reduces recharge during heavy rain. These structures reduce the amount of

ground through which rain can percolate, so excess water flows

52


58/80

The Water Table

The water table marks the top of the region underground that is saturated with water. While most

precipitation evaporates back to the atmosphere or flows directly into streams, the rest percolates down

through the ground to the water table. In the ground above the water table, a region called the aeration

zone, pore spaces are filled with a mixture of air and water.

53


59/80

WEEK ELEVEN ( 11 )11.0 Use of spring and piston analogy to substantiate neutral and effectivestresses.

When a saturated soil mass is subjected to a load increment , the load is usually carried

initially by the water in the pores because the water is incompressible in comprism with

the soil structure . The pressure which results in the water because of the load increment

is named hydrostatic excess pressure because it is in excess of that pressure due to

weight of water. As the water drains from the soil pores , the load increment is shifted to

the soil structure . The transference of load is accompanied by a change in the volume of

soil equal to the volume of water drained . This process is known as consolidation

We can be aided in understanding the consolidation process by the spring analogy shown

in fig . below . The saturated soil element is represented by fig. a , in which the spring

corresponds to the soil structure and the water to the soil pore water. If a weight W is

placed on thethe water and spring with the valve y closed ( fig . a ) , the weight is aimost

entirely carried by the water , since it is incompressible as comparedto the spring . Valve

y is opened and the water is allowed to escape , the load will eventually be carried

entirely by the spring ( fig. c ) . The elapsed time required to transfer the load increment

W from the water spring depends on how rapidly the water is permitted to escape through

valve y . The rate at which te volume change , or consolidation , occurs in a soil is

directly related to the permeability of the soil because the permeability controle the

speed at which the pore water can escape . Thepermeability of most sands is so high that

the time required for consolidation after a load application can be considered negligible

except for cases where a large mass of sand is subjected to a rapid shear or shock ( This

54


60/80

is discussed ). On the other hand , the low permeability of clay makes the rate of volume

change after a load application a factor which must be considered .

WY

WY W

Fig 11.a b cSpring anology

55


61/80

WEEK TWELVE ( 12 )

12.0 Stress Distribution in Soil due to point loads;Boussinesqs Theory

Boussinesqs stress distribution theory is based on the results given by the mathematical

theory of elasticity for the simplest case of loading of a solid , homogeneous , elastic

isotropic, semi fininite medium ; namely , the case of a single vertical point load applied

at apoint on the horizontal boundary plane . In this case of soil , the horizontal boundary

plane would be the ground surface.

P

R

R FIG.12.1 Action of a point load

M Z

R= Acos R2

56


62/80

P

I =Acos iR2

Z FIG. 12.2 Radial stresses under the

action of point load.

Y

R Z FIG. 12.3 Component stresses fora plane parallel to a boundary.

XZ

57


63/80

12.1 If a Number of point load s is applied such as p1,p2,and p3 the surfaceof the soil then compressive stress at any point of the soil.

P1 p2 p3

/////////////////////////////////////////////////////////////////////////////////////r1

r2 Z

r3

FIG. 12.4 Action of a number of point load .

AAAAAAAA AAAAA A

Stress distribution of a uniformly loaded .

dz z

58


64/80

WEEK THIRTEEN ( 13 )

13.0 CLAY SOIL

Clay, earth or soil that is plastic and tenacious when moist and that becomes permanently

hard when baked or fired. Of widespread importance in industry, clays consist of a group

of hydrous alumino-silicate minerals formed by the weathering of feldspathic rocks, such

as granite. Individual mineral grains are microscopic in size and shaped like flakes. This

makes their aggregate surface area much greater than their thickness and allows them to

take up large amounts of water by adhesion, giving them plasticity and causing some

varieties to swell. Common clay is a mixture of kaolin, or china clay (hydrated clay), and

the fine powder of some feldspathic mineral that is anhydrous (without water) and not

decomposed. Clays vary in plasticity, all being more or less malleable and capable of

being molded into any form when moistened with water. The plastic clays are used for

making pottery of all kinds, bricks and tiles, tobacco pipes, firebricks, and other products.

The commoner varieties of clay and clay rocks are china clay, or kaolin; pipe clay,

similar to kaolin, but containing a larger percentage of silica; potter's clay, not as pure as

pipe clay; sculptor's clay, or modeling clay, a fine potter's clay, sometimes mixed with

fine sand; brick clay, an admixture of clay and sand with some ferruginous (iron-

containing) matter; fire clay, containing little or no lime, alkaline earth, or iron (which act

as fluxes), and hence infusible or highly refractory; shale; loam; and marl.

59


65/80

.

Brick Wall

Bricks, blocks of baked clay, have been used in construction for thousands of years. Bricks are stacked

and bonded together with mortar to form a wall.

60


66/80

Nij Castle, Kyto

Nij Castle, in central Kyto, was built in the early 17th century by Tokugawa Ieyasu, the founder of the

Tokugawa dynasty of Japan. The walled compound is surrounded by a moat and features a wide array of

hidden defense mechanisms, including strategically placed squeaking floor boards, concealed chambers.

The earliest known African sculptures (500 BC to AD 200) are sculpted clay heads and

human figures from central Nigeria. Many surviving examples of African art date from

the 14th to the 17th century. However, most of the African art known today is relatively

recent, from the 19th century or later. Very little earlier African art has survived,

primarily because it was made largely of perishable materials such as wood, cloth, and

plant fibers, and because it typically met with intensive use in ceremonies and in daily

life. Scholars of African art base suppositions about earlier art mainly on art of the last

two centuries, but they can only guess at the earlier traditions from which the recent art

developed. 61


67/80

62


68/80

Hausa House in Nigeria

Traditional houses of the Hausa people of northwestern Nigeria and southwestern Niger are typically built

of mud, like this one in the city of Kano, Nigeria. These houses are often decorated with bas-relief

geometrical designs.

63


69/80

Ivory Salt Cellar, Sierra Leone

Europeans began collecting African art objects in the late 15th century. As the European market for such

objects increased, African artists began to create objects specifically for export. This 16th-century ivory

salt cellar was carved on Sherbro Island in Sierra Leone. Scholars have identified four of the eight figures

that ring its base as Portuguese, evidence of the influence of Portuguese traders in western Africa.

13.1 MINERALOGICAL STUDY OF CLAY

Clay minerals are predominantely a group of complex alumino silicates, mainly

formed durjng the chemical weathering of primary minerals . these minerals are

predominantly crystalline in that the atoms composing them are arranged in definite

geometrical patterns.

There two fundamental building blocks for the clay mineral structure . One is a silica

unit ( fig. N4 -1 ) in which four oxygen ions ( O2- ) FORM THE TIPS OF A

TETRAHEDRON and enclose a silicaon ion ( Si 4+ ) . The two units are held together by

ionic bonds. The other unit is one which an aluminium or magnesium. As shown below

= O 2-

= Si 4+

A TETRAHEDRAL UNIT

64


70/80

= ( OH )-

= Al

2+

FIG 2 OCTAHEDRAL UNIT

65


71/80

WEEK FOURTEEN ( 14 )

14.0 Formation of two layer soils with typical example like kaolinite;

Kaolin (Chinese kaoling,high ridge), or china clay, a pure, soft, white clay of variable

but usually low plasticity that retains its white color when fired. The material was first

obtained from a hill called Kaoling and was sent to Europe in the early 18th century. Pure

kaolin is used in the manufacture of fine porcelain and china; impure varieties are used in

making pottery, stoneware, and bricks; as filler for pigments; and in the manufacture of

paper. The chief constituent of kaolin is the mineral kaolinite, a hydrous aluminum

silicate, Al2Si2O5(OH)4, formed by the decomposition of aluminum silicates, particularly

feldspar. Kaolin is now mined primarily in South Carolina, North Carolina, Georgia,

Pennsylvania, and Alabama. The term kaolin is often extended to include other porcelain

clays not discolored by firing.

Kaolin Mine

Georgia leads the nation in kaolin production. Kaolin is a soft white clay used in the manufacture of china,

bricks, and paper, among other things. This is an open pit kaolin mine.

Georgia Department of Industry, Trade and Tourism

66


72/80

14.1 Clay Minerals.

An outstanding accomplishment during the year was the publication of four volumes on

the clay minerals. About 20 scientists from 8 research laboratories, both public and

private, contributed to these studies, which are numbers 5 to 8 of a series sponsored by

the American Petroleum Institute's Project 49 on 'Clay Mineral Standards.' The clay

minerals play an important role from beginning to end in the natural history of an oil

deposit, and the aim of the project is to determine all that can be learned by chemical

analyses, thermal analyses, infra-red spectra, X-ray diffraction measurements, optical

properties, and electron micrographs of the kaolin, montmorillinite, and illite groups of

clay minerals, plus a few closely related minerals. In the four volumes appearing in 1950

all of these approaches were followed. Success of this project further illustrates what can

be done through organized group research.

The montmorillonite clay is made of sheet like units ordered , also as a 1; 2 unit , as asschematically illustrated in the fig. N4-6

G

SI n H2O + anyMetallic

Si

Fig. N4-6

67


73/80

WEEK FIFTEEN ( 15 )

15.0 SOIL

Soil, the loose material that covers the land surfaces of Earth and supports the growth of

plants. In general, soil is an unconsolidated, or loose, combination of inorganic and

organic materials. The inorganic components of soil are principally the products of rocks

and minerals that have been gradually broken down by weather, chemical action, and

other natural processes. The organic materials are composed of debris from plants and

from the decomposition of the many tiny life forms that inhabit the soil.

Soils vary widely from place to place. Many factors determine the chemical composition

and physical structure of the soil at any given location. The different kinds of rocks,

minerals, and other geologic materials from which the soil originally formed play a role.

The kinds of plants or other vegetation that grow in the soil are also important.

Topographythat is, whether the terrain is steep, flat, or some combinationis another

factor. In some cases, human activity such as farming or building has caused disruption.

Soils also differ in color, texture, chemical makeup, and the kinds of plants they can

support.

Soil actually constitutes a living system, combining with air, water, and sunlight to

sustain plant life. The essential process of photosynthesis, in which plants convert

sunlight into energy, depends on exchanges that take place within the soil. Plants, in turn,

serve as a vital part of the food chain for living things, including humans. Without soil

there would be no vegetationno crops for food, no forests, flowers, or grasslands. To a

great extent, life on Earth depends on soil.

68


74/80

The study of different soil types and their properties is called soil science or pedology.

Soil science plays a key role in agriculture, helping farmers to select and support the

crops on their land and to maintain fertile, healthy ground for planting. Understanding

soil is also important in engineering and construction. Soil engineers carry out detailed

analysis of the soil prior to building roads, houses, industrial and retail complexes, and

other structure.

Stages of SoiFormation

Soil formation is the process by which rocks are broken down into progressively smaller particles and

mixed with decaying organic material. Bedrock begins to disintegrate as it is subjected to freezing-thawing

cycles, rain, and other environmental forces (I). The rock breaks down into parent material, which in turn

breaks into smaller mineral particles(II). The or

soil mechanics book - internet

Documents