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Home , Soil mechanics

GATE –

GEOTECHNICAL ENGINEERING

Prof.B.Jayarami Reddy Professor and Head Department of Civil Engineering Y.S.R. Engineering College of Yogi Vemana University, Proddatur, Y.S.R.(Dt.), A.P-516360.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 1 GATE – CIVIL ENGINEERING List of Subjects: 1. General Aptitude 2. Engineering Mathematics 3. Engineering Mechanics 4. Solid Mechanics 5. Structural Analysis 6. Concrete Structure 7. Steel Structures 8. Construction Materials and Management 9. Geo Technical Engineering 10. Fluid Mechanics 11. 12. Water Resources Engineering 13. Environmental Engineering 14. Transportation Engineering 15. Geomatics Engineering

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 2

8.0 MECHANICS 9.0 ENGINEERING 8.1 Origin of 9.1 Soil Exploration and Field Tests 8.2 Basic Definitions and Relations 9.2 Earth Theories 8.3 Index Pproperties of Soils 9.3 Stability of Slopes 8.4 9.4 Distribution in Soils 8.5 9.5 Foundation Types and 8.6 Permeability 9.6 Deep Foundations 8.7 Seepage Analysis 9.7 Miscellaneous Topics 8.8 Consolidation and Settlement Analysis 8.9 Compaction 8.10

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 3 8.1 ORIGIN OF SOILS Father of Soil Mechanics –Karl Terzaghi Formation of Soils: • Soil is naturally occurring unconsolidated earth material above the bed . • When large size rocks and boulders are exposed to atmosphere, it will undergo physical disintegration and chemical decomposition due to atmospheric agencies and hence leads to formation of soils. • is a process of formation of soil.

Weathering

Transportation Upheaval Deposition

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 4 Boulder Cobble Pebble Formation of soil particles from Rocks Formation of Soils: • Soils are formed by 1. Weathering of rocks 2. Geological agents 1. Weathering of Rocks: Weathering process a. Mechanical / Physical Weathering b. Chemical Weathering c. Biological weathering a. Physical weathering: • Due to physical effects like temperature, abrasion, wedging action of ice, etc., • No change in chemical composition of particles • Results in Coarse grained and non cohesive soils. Prof. B. Jayarami Reddy Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 5/13/2020 5 • Soils are formed by 1. Weathering of rocks 2. Geological agents 1. Weathering of Rocks: Weathering process a. Mechanical / Physical Weathering b. Chemical Weathering c. Biological weathering a. Physical weathering: • Due to physical effects like temperature, abrasion, wedging action of ice, etc., • No change in chemical composition of particles • Results in Coarse grained and non cohesive soils. b. Chemical weathering: • Original rock minerals are transformed into clay minerals. • Results in fine grained and cohesive soils. i. Oxidation ii. Hydration iii. Carbonation iv. Solution or v. Hydrolysis

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 6 c. Biological Weathering: • Bacterial and other organisms produces some organic acids which induces chemical changes in their surroundings. • Organic soils are formed due to Biological weathering. eg: , Humus. • Organic soils are called as Cumulose soils. 2. Geological Agents: • Geological agents are the natural forces which are responsible for modifying irregularities on the earth surface. • Classification based on origin: a. Endogenous geological agents b. Exogenous geological agents

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 7 a. Endogenous Geological Agents: • Originate below the earth surface. • Creates topographic irregularities eg: Volcanic eruption, earth quakes, Ground water, etc., b. Exogenous Geological Agents: • Originates above the earth surface. eg: River, Wind, Ocean, , etc. • Transport the rock minerals from one place to another place. • During transportation it causes breakdown of soil mass due to abrasion and attrition.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 8 Types of soils: 1. Based on transportation a. Sedimentary soils (Transported soils) b. Sedentary soils / Residual soils a. Sedimentary Soils: • Soil particles created at one location, transported and finally deposited in another location. Source of Transportation Type of soil Examples

Lakes Lacustrine soil

Rivers and streams Alluvial soil

Sea Marine soil Marine and clays

Wind Aeolian soil Sand, Dunes,

Gravitation Colluvial soil Talus

Glacier Glacial soil Drift, Till, Moraines

River soil near ocean Estuarine soil Soil near Estuaries

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 9 b. Residual soils / Sedentary soils: • Soils which remain on the parent rock without getting transported. eg: Black cotton soils, laterite soils. i. Black Cotton Soils: • Formed due to chemical weathering • Parent rock is basalt or trap • Exhibits large swelling and shrinkage due to presence of . ii. Laterite Soils: • Formed due to Leaching of some minerals away from parent rock • Red or Pink colour is due to Iron Oxide. 2. Based on average grain size a. Coarse grained soils: Avg. size >0.075mm eg. and b. Fine grained soils: Avg. size <0.075mm eg. Silts and Clays

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 10 Forces acting on the soil particles: a. Gravitational force or body force: • Body force is proportional to the mass. • Predominant in Gravel and sand. b. Surface Force: • It is proportional to surface area. • • Predominant in clay – clay behaviour is mainly controlled by surface force. In silty soils both body force and surface force are to be considered.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 11 Commonly used Soil Designations: 1. Varved Clay: Alternate layers of silt and clay. eg: lacustrine deposits 2. : Mixture of Sand, Silt and Clay 3. : Conglomorite of gravel, sand and clay cemented by Calcium Carbonate. 4. Moorum: Gravel mixed with red clay

Varved clay Loam soil Caliche soil Moorum soil

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 12 5. Bentonite: Obtained due to weathering of Volcanic ash Contains high percentage of montmorillonite clay mineral Exhibits high degree of shrinkage and swelling 6. Boulder clay: clay containing all sizes of particles from boulder to clay. It is also called as Glacier till. 7. Hard Pan: Very difficult to penetrate or excavate. eg: Glacial till, Boulder clays Densely cemented soil which remains hard when wet 8. Loess : Uniform wind blown yellowish brown silt or silty clay Exhibits cohesion in dry condition, which is lost on wetting.

Bentonite Boulder clay Hard pan soil Loess

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 13 9. Marl: Mixture of calcarious sands or clays or loam Clay < 75 % , Lime > 15% 10. Top soil: Surface material which supports plant life. 11. Fill: All man made deposits 12. Tuff : Very fine particles ejected from volcanoes and deposited by wind or water

Marl Top soil Fill soil Tuff

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 14 13. Peat: • Highly decomposed organic matter and Fibrous in nature. • Dark brown to black colour and Bad odour. 14. Humus: • It consists of partly decomposed organic matter. • It is dark brown, organic amorphous earth of the soil 15. Muck: • Partly containing fine inorganic particles and partly decomposed organic matter.

Peat Humus Muck Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 15 16. Black Cotton soil: • Clay obtained due to chemical weathering. • Parent rock – Basalt or Trap • Exhibits large swelling and shrinkage characteristics due to presence of montmorillonite clay mineral. 17. Tundra: It is a mat of leaf and shrubby vegetation-covers clayey clumsy . • Below the soil is tundra's , a permanently frozen layer of earth. • In tundra, soil is very low in nutrients and minerals • The soil becomes frozen a short ways below the ground due to low temperatures.

Black cotton soil Tundra Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 16 18. Till: • A part of glacial drift which in directly deposited by ice. • A Glacial clay characterised by directly marked annual deposit of sediments.

Till

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 17 8.2 BASIC DEFINITIONS AND RELATIONS

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 18 8.2 BASIC DEFINITIONS AND RELATIONS Phase Diagram:

• Soil mass - Three phase system - composed of solid, liquid and gaseous matter. • Voids - Spaces enclosing the Solids • Liquid phase is water that fill partly or wholly the voids. • Gaseous phase (air) occupies the voids not filled by water. • Three constituents are blended together to form a complex material. Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 19

Three Phase System: a. Volume: Total Volume = Volume of Solids + Volume of voids

Volume of voids = Volume of water + Volume of air.

b. Weight: Total weight = Weight of soils + Weigh of voids.

Weight of voids = Weight of water +Weight of air. Weight of air is assumed to be zero.

Total weight = Weight of solids +Weight of water.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 20 Two Phase Diagram: Soil becomes two phase system in some special cases. 1. When all the voids are filled with water, the sample becomes saturated thus gaseous phase is absent. 2. When the soil is absolutely in dry condition, the water phase disappears.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 21 Fundamental definitions: (e ): volumeof voids V e v 100 volumeof solids Vs  can have any value greater than 0.  sometimes may be greater than 1. (0 e   )  void ratio for coarse grained soils is generally less than that for fine grained soils.  when spherical grains are arranged in cubical array the maximum possible .  When spherical grains are arranged diagonally, void ratio is least.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 22  When spherical grains are arranged in cubical array, the void ratio is maximum.  When spherical grains are arranged diagonally, void ratio is least.

Cubical array of spherical Diagonal arrangement of spherical grains (Loosest state)e  0.91 grains (Densest state)e  0.35  Void ratio for fine grained soils is more than that for coarse grained soils.

V2 V1

Rice VV21 Rice Flour

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 23 : () n

Volumeof voids V n  100 v  100 Total volumeof soil V

• Range 0n 100% • also called Percentage of voids.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 24 Degree of saturation: () S Volumeof water V S  100 w  100 Volumeof voids V v  for fully saturated soil, S = 100% or 1  for dry soils, S  0  Range: 0 to 100%

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 25 Air Content:() a c Volumeof air voids V a  100 a  100 c Volumeof voids V v

 for a saturated soil, ac  0  for a dry soil, a c 1  Range: 01ac

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 26 Percentage of Air voids

Volumeof air voids Va na   100 Total volume V

• for saturated soil, na 0 • for dry soil, nna 1 • Range: 0 nna

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 27 or Moisture content: () w

Weight of water W • Water content, w 100 w  100 Weight of solids W s • can have any value greater than 0. • can be greater than 100%.

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 28 Bulk (or Mass) : () Total weight of soil W   Total volumeof soil V

WWW sw VVVVs  w  a

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 29 Dry density: ()  d Weight of solids W  s d Total volume of dry soil V

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 30 Saturated density: () sat Weight of soil when the soil is fully saturated W WW     sw sat Totalvolume of soil VV

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 31 Submerged unit weight: () 

().WWVs subWeight of solidssubmerged sat  w '    sat   w VVTotal volume of soil • Buoyant force F B on the soil acts in the upward direction. • Buoyant force is based on the Archimedes principle. • Buoyant force for the submerged soil is equal to weight of water displaced by the soil. Wsat

FVBw .

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 32 Unit weight of solids: () s

Weight of solids Ws  s  Volumeof solids Vs

  s is constant for a given soil, where as  d is not constant

Unit weight of Solids > Saturated unit weight > Bulk unit weight > Dry unit weight > Submerged unit weight. s  sat     d   

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 33 Specific gravity:() G It is the ratio of weight of a given volume of soil solids at a given temperature to the weight of an equal volume of distilled water at that temperature. As per I.S. code standard temperature for measuring G is 270C

Unit weight of solids  s Ws G  or G   Unit weight of water  W w w Same volume for a given soil, G remains constant. Generally G for soils lies between 2.60 to 2.85.  1000kg/m33 1t/m w 33 9.81kN/m 10kN/m 1g/cm3

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 34 Apparent or Mass or Bulk Specific gravity: () Gm Mass or Bulk unit weight of soil  G  m Unit weight of water  w  sat  Mass Specific gravity in Saturated condition   w  d  Mass Specific gravity in Dry condition   w

• G m is not constant.

GGm  • eg. Specific gravity of cement: 3.15 Unit weight of cement: 1440 kg/m3 1440 Massspecificgravityof cement,G  1.44 m 1000 Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 35 Some important relationships: 1. Relation between n and e : V V v e  v n  V Vs

1VeVVV 1 1  s v  s 11    n Vvvv V V e e

e n n  e  1 e 1 n

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 36 2. Relation between n , a and S a c ac Air na Air

V V V V 1 n a  a S  w n  a n  v S Water Water c V V a V V v v 1 VVV a v a Solids n.. aca   n nac n. a Solids VVV v

VVVVVa w a w v aS     1 aSc 1 c Vnaa VVVVv v v v aSc 1 a  c Vn v Sa1 aS1 na  n(1 S ) c c

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 37 3. Relation between S ,, w G and e : Air V W V  s e S  w w  w e  v G  Se. Water Ww w... V w w S e V W V  w v s s VVV Se..w v w 1 WV.   .1   VVVv s s Solids s s s s s

WVVVw w.. w w w w Se. wG. w      S WVVGVGGs s.... s s w s e W.... S e S e Se. For saturated condition, w w  w  w  S 1 e wsat . G WGG. s s w wG. S  e

Prof. B. Jayarami Reddy Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 5/13/2020 38

4. Relation between  ,, GS and e

W WWWWW(1 / )   s w  s w s Air VVVVVV(1 / ) e s v s v s Se. Water Ww w... V w w S e (1 ww ) 1 G wG. sw..G  . (1ee ) 1 1 e w G Se  1 WV.   .1    . w Solids s s s s s 1 e  Ge  .  For Saturated soil ( S  1) , sat w 1 e

G. w W W W.. S e  (S  0) s w s w For Dry soil ,  d      1 e V Vsv V1 e G Se Gww   S.. e  . w      G... S e G S. e 1e 1  e   1  e  ww  w 11ee Ge G w  dw .      S()    11ee d sat d Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 39

5. Relation between  sat , w and   ()W    s sub V

():Ws sub Weight of solids in air -Weight of water displaced by the solids WVWWVWVV ....          s s w w s w w w s w WVVWV ().    w w s w (W W s)sub      VVw sat w

G e G  e (1  e ) G 1  . w   w   w   . 11ee w 1 e Gww     dw (1  n )  11ee   dw (1  n ) 

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 40

6. Relation between  , d and w Air

WWWw w s W 11w     w Water WWWs s s WV   1.w    d  VW  1 w Solids 1 sd

W WW s  W  1 1wws 1

W W(1 w ) s d (1w )

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 41

7. Relation between GGS ,, m and e  G S. e Gm   1 e w

Gmm G.. e  G  S e e() Gmm S  G  G

GG e  m GSm  G  For Dry condition ( S  0) , Gm  1 e Ge  For Saturated condition ( S  1) , G  m 1 e

8. Relation between  d,  a ,G,  d , and e

(1 nGaw ) .  d  1 e Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 42

9. Relationship between volume of soil and void ratio: Vs V Ws 1 Ve1  dd   11 e VV Air e Water V,,, e W 11 ds1 V,,, e W 22ds2 V e  v Borrow Pit Vs 1 Solids Ve1 11

Ve221

Ve1  11d 2 Ve21 2 d 1

Prof. B. Jayarami Reddy 5/13/2020 Y.S.R. ENGINEERING COLLEGE OF YOGI VEMANA UNIVERSITY, PRODDATUR 43