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Soil Mechanics

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a brief of soil mechanics with various IS code

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Soil Mechanics

  1. 1. Presented by Er.Krishan Dev (Arkitechno India Pvt. LTD.) Presented to 1
  2. 2. I. Soil Mechanics II. Soil III. Soil Classification IV. Physical Properties V. Hydraulic Properties VI. Mechanical Properties VII. Application of Soil Mechanics VIII. Liquefaction IX. Expansive Soil X. Soil Stabilisation XI. Major soil deposits in India XII. Conclusion XIII. Reference Books 2
  3. 3.  Discipline of Civil Engineering, involves study of soil, its behaviour and application as an engineering material.  Involves the law of mechanics and hydraulics to soil engineering problems. • Mechanical law : SBC, Settlement, strength. • Hydraulics law : Seepage, Well, Permeability.  Father of Soil Mechanics: Karl Von Tarzaghi. • Term Soil Mechanics is coined by him in 1925.  Grandfather of soil mechanics : Coulomb (1776). • Shear strength is combination of cohesion and angle of internal friction. 3
  4. 4.  Generated by weathering of Rocks and Geological cycle. Mechanical weathering Chemical weathering •Soil contains original composition of the parent rock. •Composition of soil has been altered by chemical reactions. •Mainly Cohesionless soil. •Mainly Cohesive soil •Forcing agents: Forcing agents: • Wind • Temperature change •Oxidation •Leaching by water • Animal • Ice •Hydration •Leaching by organic acids • Water • Plants •Carbonation 4
  5. 5.  Different meaning to different fields. • Padologist : Substance support plant life. • Geologist : Substance cover earth surface. • Engineer : material can be used for  Built on : foundation of structures.  Built in : Tunnel, basements.  Built with : Embankments, Roads, Dam.  Support : Retaining wall. 5
  6. 6.  Weathering • Residual • Transported  Alluvial  Marine Water Transported.  Lacustrine  Glacial Drift - Glaciers  Aeoline - Wind Blown  Colluvial - Gravity  Particle size and Texture. • Coarse or fine grained  Density and void ratio. • Loose or Dense  Swelling Index. • Expansive or Non expansive  Highway Research Board. • Good or Inferior  USCS System • Coarse or fine grained (well or poorly graded, plasticity level) 6
  7. 7.  Combination of Air, Water (Voids) and solids.  Variation of these three provide uniqueness to soil.  Heterogeneous.  Not behave linearly.  Therefore to understand the behaviour of soil we have to understand its Properties. • Physical Properties . • Mechanical Properties. • Hydraulic Properties. 7
  8. 8. Name of properties Method of determination IS Code UsedLab. Field Water content = Wt. Of water/Wt. Of solids •Oven Drying •Pycnometer •Sand bath •Alcohol •Calcium Carbide I.S 2720 (5) I.S 2720 (2) Specific Gravity = Unit wt. Of soil solids/unit wt. Of water •Pycnometer •Density Bottle I.S 2720 (3) Particle Size Distribution •Sieve Analysis a. Coarse sieve b. Fine Sieve •Sedimentation analysis a. Pipette method b. Hydrometer method I.S 2720 (4) 8
  9. 9. Name of properties Method of determination IS Code UsedLab. Field Bulk Density = Mass of soil/Vol. Of soil •Water displacement •Rubber balloon •Submerged mass density •Sand replacement •Core cutter IS 2720 (33) I.S 2720 (28) I.S 2720 (29) Dry density = Dry mass of soil solids/ Total vol. of soil •By relationship of bulk density and water content IS 2720 (7,8 and 9) Void ratio = Vol. Of voids/ Vol. Of solids •By relationship of dry density IS 2720 (7 and 8) Liquid Limit = soil is in liquid but having small shearing strength. •Casagrande •Static cone penetration I.S 2720 (5) Plastic Limit = soil starts crumble at a dia. Of 3 mm. •Thread method I.S 2720 (5) Shrinkage Limit = decrease in water not lead to vol. Change. •Shrinkage limit apparatus I.S 2720 (6) 9
  10. 10. Name of properties Method of determination IS Code UsedLab. Field Permeability = Permits the passage of fluid •Constant head •Falling head •Consolidation •Pumping in •Pumping out IS 2720 (17) IS 5529 (1) Specific yield = Vol. Of water drained by gravity/ Total vol. • By Grain size Specific Retention = Vol. Of water retained by gravity/ Total vol. •By Grain size Seepage pressure = pressure exert by water on soil •Flow net 10
  11. 11. Name of properties Method of determination IS Code Used Lab. Field Shear Strength •Triaxial •Direct shear •UCS •Vane shear •SPT •CPT IS 2720 (11) IS 2720 (13) IS 2720 (10) IS 4434 IS 2131 IS 4968 Settlement = decrease in volume. •Consolidation •Compaction •Proctor needle •Plate load IS 2720 (15) IS 2720 (7 & 8) - IS 1888,921 4 Slope Stability = Inclined soil structure •Shear strength and Shear stress •Swedish slip circle •Taylor stability no. Lateral Earth Pressure = Transverse Pressure Exerted by soil. •Cohesion and Angle of internal friction, •Rehbann, Culmann, Rankine 11
  12. 12. Name of properties Method of determination IS Code Used Lab. Field Safe Allowable Bearing Capacity = Should fulfil bearing and settlement Criteria •Shallow: •Cohesion and Angle of internal friction •Pile: •Dynamic Formula •Static Formula •Plate Load •SPT •SCPT •Pile Load •Cone Penetration IS 6403 IS 8009 IS 2950 (1) IS 2911 (1,2,3) IS 1888 IS 2131 IS 4968 (3) IS 2911 (4) IS 4968 (3) Stress Distribution = Mobilisation of stress under a footing. •Soil Type •Boussinesq •Westergaard 12
  13. 13. Shallow Footings Strip Spread Combined Rafts 1.1Foundation Design : Transfer super structure load to soil.  Design : Allowable Bearing Capacity. D/B ≤1 13
  14. 14. Deep Pile Load (End and Friction) Material (Timber, Steel, Concrete) Function (Tension, Compressio n) Casting (Pre and In-situ) Pier Drilled Excavated Caissons Box Open Pneumatic D/B ≥1 14
  15. 15. Ground water table. Soil Type. Stress distribution. Vibration. Load. Expansiveness. Scour. 15
  16. 16. 1.2 Pavement Design : Rigid or Flexible both transfer load to soil subgrade.  Design : Allowable Bearing Capacity Bearing Capacity, Penetration.  Keep in Mind : Load Repetition. Fatigue. Frost. Heave. Thaw. Swell and Shrinkage. 16
  17. 17. 1.3 Underground and Earth Retaining structure: o Underground : Tunnel. Basements, Pipe, Conduits. o Retaining : Retaining Wall, Cofferdam. o Design : Lateral Earth pressure. o Keep in mind : Soil structure Behaviour. Initial standing time. Initial standing height. 17
  18. 18. 1.4 Embankment and Excavation : Slope tries to move downwards because of gravity, undercutting, seepage etc.  Design : Slope Stability.  Keep in mind : Height of slope. Resisting Force. Driving Force. Shear strength. FOS Seepage. Earthquake. 18
  19. 19. 1.5 Earth Dams : Restrict the flow of water  Design : Seepage analysis, slope stability, consolidation, Allowable Bearing capacity.  Keep in mind : OMC and Dry density. Plasticity characteristics. Permeability. Specific Gravity. Particle size distribution. Flow Net. Gradation of soil. Hoover Dam on Colorado river Earthquake. (U.S. State of Nevada & Arizona) 19
  20. 20.  Liquefaction : Key for fixing foundation depth in saturated loose sand and seismic zone.  Soil looses its all shear strength and behave as a liquid.  Reason : High strain lead to un drained condition.  Pore water pressure increases and effective stress decreases. Niigata EQ (1964)  Key note : • EQ induced Shear stress < Shear strength of soil. • Can occur only if saturated sand is at shallower Depth < 12m. • Can occur only if SPT N value is less then twice of depth. 20
  21. 21.  High potential to volume change.  Reason : • Clay mineral (Montmorillonite). • Osmosis. • Hydrated cation.  Methods to Measure : • Differential free swell test. • Cole • Clay content • CEC and Ac  Prevention : • Under ream Pile , Electro kinematics, Chemical stabilisation. 21
  22. 22. Mitchel 1972 22
  23. 23. Name of soil Places where it is found Black Cotton Maharashtra, Gujarat, Madhya Pradesh, Andhra Pradesh, Tamil Nadu, Karnataka. Marine soil Coast Line, Rann of Kutch. Desert soil Rajasthan Alluvial soil Indo-Gangetic plain, North of Vindhyanchal Laterite Kerala, Odisha, Karnataka, West Bengal, South Maharashtra. 23
  24. 24.  Any structure which depends upon soil in any manner needs the crystal knowledge of soil mechanics.  Soil mechanics provides tools to understand the behaviour of soil.  Soil mechanics is base of foundation engineering as well as other design. 24
  25. 25. MUNI BUDHU B.C. PUNMIA C. VENKATRAMAIAH BRAJA M. DAS JOSEPH E. BOWELS SWAMI SARAN 25
  26. 26. THANK YOU 26

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