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1.ce206 lecture 1-2
1. CE 206CE 206 Geotechnical EngineeringGeotechnical Engineering --IICE 206CE 206 Geotechnical EngineeringGeotechnical Engineering II
Syllabus
Origin of soil, Phase relationships, Identification and
classification of soils, Effective stress principle,, p p ,
Permeability of soils, Compressibility of soils, Seepage
and flownets, Terzaghi’s one-dimensional consolidation, g
theory, Shear strength of soils, Effective stress and total
stress strength parameters, Total and effective stressg p ,
paths, Compaction of soils.
2. Textbooks & References
G l R j d R A S R B i d A li d S il M h i N A Gopal Ranjan and Rao, A.S.R. Basic and Applied Soil Mechanics, New Age
International, 2000.
Coduto, D. P., Yeung, M. C. and Kitch, W. A, Geotechnical engineering: principles and, , g, , , g g p p
practices, New Delhi : PHI, 2011
Kaniraj, S.R. Design Aids in Soil Mechanics & Foundation Engineering, Tata McGraw
Hill 1988Hill, 1988.
Holtz, R. D. Kovacs, W. D. and Sheahan, T. C. An Introduction to Geotechnical
Engineering, Second edition, Pearson, 2013.
Budhu, M. Soil Mechanics and Foundations, 2e, Wiley India Pvt. Ltd., 2008
Terzaghi, K., Peck R. B. and Mesri, G. Soil Mechanics in Engineering Practice, John
Wiley & Sons 1996Wiley & Sons, 1996.
Lambe T.W. and Whitman, R.V. Soil Mechanics, John Wiley & Sons, 1969.
Indian Standard Codes of Practice (IS 2720)( )
3. Origin of SoilOrigin of Soil
CE 206CE 206 Geotechnical EngineeringGeotechnical Engineering IICE 206CE 206 Geotechnical EngineeringGeotechnical Engineering --II
Department of Civil Engineering
Indian Institute of Technology GuwahatiIndian Institute of Technology Guwahati
4. SoilSoil
Originated from the Latin word Solum
Different meaning for Different Professions
Agriculturist
The top thin layer of earth within which organic forces are
predominant and which is responsible for the support of plant life
Geologist
The material in the top thin zone within which roots occur.p
Engineer
soil includes all earth materials organic and inorganic occurring in soil includes all earth materials, organic and inorganic, occurring in
the zone overlying the rock crust
Soil is defined as the uncemented aggregate of mineral grainsSoil is defined as the uncemented agg egate of mine al g s
and decayed organic matter (solid particles) with liquid and gas
in the empty spaces between the solid particles
5. Soil formationSoil formation
Soils are formed by weathering of rocks
Size of the individual grains varies over a wide range
Physical properties of soil Physical properties of soil
Dictated by size, shape and chemical composition
primarily by the minerals hat constituted the soil particles i e the primarily by the minerals hat constituted the soil particles i.e the
rock from which it is derived
So knowledge on types of rocks and weathering process So knowledge on types of rocks and weathering process
6. WeatheringWeathering
The process of breaking down rocks by physical
(mechanical), chemical and biological processes into
smaller pieces
Physical or Mechanical weathering
By physical processy p y p
Impact, grinding and erosive action of water, ice and wind
Opening of cracks as a result of unloading due to the erosion ofOpening of cracks as a result of unloading due to the erosion of
overlying soil and rock
Retain minerals of parent rockp
Chemical weathering
Oxidation hydration carbonation leaching by organic acids of Oxidation, hydration, carbonation, leaching by organic acids of
water
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8. Different Rock TypesDifferent Rock Types
Based on the mode of origin 3 types
Igneous Rocks
formed by the solidification of the molten magma ejected from deep within
the earth's mantlethe earth s mantle
Depending on type of minerals present in magma and rate of cooling
different types of igneous rocks are formed
Sedimentary Rock
Soil deposits transformed back into rocks through hardening process
Clastic rocks
Carbonates
Metamorphic Rock Metamorphic Rock
Metamorphisum the process of changing the composition and
texture of rocks without melting by heat and pressuretexture of rocks, without melting, by heat and pressure
10. Composition of some Igneous Rocks (Das 2006)Composition of some Igneous Rocks (Das, 2006)
11. Rock MineralsRock Minerals
Feldspar
Quartz
Ferromagnesian minerals Ferromagnesian minerals
Iron oxides
C l i Calcite
Dolomite
Mica
Gypsum Gypsum
12. SoilsSoils
Residual soils
Rock weathering products located at the place where they
originated
Not common
Transported soilsp
Transported from the place of origin
By wind, water, ice or any other agencyy , , y g y
Characteristics of soil such as size of particles their shape,
roundness, surface texture and degree of sorting areroundness, surface texture and degree of sorting are
influenced by agency of transportation
13. Residual soilsResidual soils
When rock weathering process is faster than the transport
process
Retains many of the characteristics of the parent rocky p
Tropical regions
Very thick residual soils (~ 100s of meters) over unweathered Very thick residual soils ( 100s of meters) over unweathered
rock
Called Literites – cemented with iron oxides having high dry strengthg g y g
Cooler and more arid regions
Much thinner layers (may be no residual soil) Much thinner layers (may be no residual soil)
Soil type depends on parent rock
D p d it d id l il Decomposed granite- sandy residual soil
Shale type sedimentary rock - clayey residual soils
14. Different soils based on depositionDifferent soils based on deposition
Alluvial Deposits
From suspension of running water
Lacustrine Depositsp
Suspensions in still and fresh water of lakes
Marine Deposits Marine Deposits
Sea water suspensions
A li D it Aeolian Deposits
Transported by wind
Glacial Deposits
Transported by ice
15. Effects of Transportation on Sediments (L b & Whit 1969)Effects of Transportation on Sediments (Lambe & Whitman 1969)
16. Alluvial SoilsAlluvial Soils
Transported to their present position by rivers or streams
Very common
Contains extensive ground water aquifers Contains extensive ground water aquifers
When flow is rapid
Sil d l i i i Silts and clays remain in suspension
Only sands, gravels, and boulders deposited
f f If flow is slow
More of finer soils also deposited
Alluvial soils often contain alternating horizontal layers of
different soil types
Formation of different soils during different seasons due to
different flow rates
17. Alluvial fans
Deposits formed at the foot of a canyon
Common in arid regions
In steep terrains
Large boulders are carried by waterLarge boulders are carried by water
Subsequently covered with finer soils
Causes extensive problems when attempted for exploratory Causes extensive problems when attempted for exploratory
borings or to make excavations or drive pile foundations
Most alluvial soils have moderately good engineering Most alluvial soils have moderately good engineering
properties
Typically provide fair to good support for buildings and Typically provide fair to good support for buildings and
other structures
18. Lacustrine soilsLacustrine soils
Deposited beneath lakes
May still be under water
Or exposed due to lowering of lake water level
Primarily silt and clay
Suitability for foundation ranges from poor to average Suitability for foundation ranges from poor to average
19. Marine soilsMarine soils
Deposited underwater in the ocean
Deltas
Formed where rivers meet larger bodies of waterg
Creates flat terrain – water flows very slowly
Primarily silts and clays,--- very softPrimarily silts and clays, very soft
Beach sands – typically poorly graded, well rounded and
looseloose
Deeper marine deposits
M if More uniform
Often contain organic material from marine organisms
20. Most lacustrine and marine soils are very uniform and
consistent
Engg. Properties are often poor but may be moregg p p y
predictable than the other more erratic soils
21. Aeolian soilsAeolian soils
Deposited by wind
Produces very poorly graded soils
Due to strong sorting power of windg g p
Usually very loose
Onl fair engineering properties Only fair engineering properties
Three types of wind induced transport
Suspension
Lifting individual silt particles to high altitude and transport
S l i Saltation
Intermediate process—soil particles temporarily airborne and then fall
backback
Creep
Occurs in particles too large to airborne – medium to coarse sands
22. Modes of sediment transport by the wind (after Pye,
1987)1987)
D t t i IDust storm in Iraq
(after Lancaster 2009)
Forms sand dunes
Loess- thick Aeolian silts
23. Colluvial soilsColluvial soils
Transported down by gravity
Two types of movement
Slow
In the order of mm per year, called CREEP
Rapidp
Landslides or mudflows
24. Major Indian SoilsMajor Indian Soils
Black cotton soils
i i M h h G j M dh P d h K k f occurring in Maharashtra, Gujarat, Madhya Pradesh, Karnataka,parts of
Andhra Pradesh and Tamil Nadu.
These are expansive in nature. On account of high swelling and shrinkagep g g g
potential these are difficult soils to deal with in foundation design
Marine soils
occurring in a narrow belt all along the coast, especially in the Rann of Kutch.
These are very soft and sometimes contain organic matter, possess low
strength and high compressibility.g g p y
Desert soils,
occurring in Rajasthan. These are deposited by wind and are uniformly graded.
Alluvial soils
occurring in the Indo-Gangetic plain, north of the Vindhyachal ranges.
Lateritic soils,
occurring in Kerala, South Maharashtra, Karnataka, Orissa and West Bengal.