More Related Content
What's hot
What's hot (20)
Similar to EARTH PRESSURE - GTE.pptx
Similar to EARTH PRESSURE - GTE.pptx (20)
More from Samirsinh Parmar
More from Samirsinh Parmar (20)
Recently uploaded
Recently uploaded (20)
EARTH PRESSURE - GTE.pptx
- 1. -By Prof. SAMIRSINH.P.PARMAR DEPARTMENT OF CIVIL ENGINEERING DHARMASINH DESAI UNIVERSITY, NADIAD
- 2. CONTENT OF THE PRESENTATION Earth pressure introduction Types of retaining walls Uses / Application of Earth pressure theories Definitions / Terms Active / Passive earth pressure Ko condition Rankine's earth pressure theory Coulomb's earth pressure theory Cullman's earth pressure theory Mode’s of retaining wall failure Some pictures explaining QC 2 Earth Pressure, SPP_CL, DoCL, DDU- Nadiad
- 3. WHERE EARTH PRESSURE? Calculating lateral earth pressure is necessary in order to design structures such as: Retaining Walls Bridge Abutments Bulkheads Temporary Earth Support Systems Basement Walls Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 3
- 4. TYPES OF RETAINING WALLS: Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 4
- 5. USE OF RETAINING WALLS Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 5
- 6. USE OF RETAINING WALLS Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 6
- 7. IN GEOTECHNICAL ENGINEERING, IT IS OFTEN NECESSARY TO PREVENT LATERAL SOIL MOVEMENTS Cantilever retaining wall Braced excavation Anchored sheet pile Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 7
- 8. DEFINITION OF KEY TERMS Active earth pressure coefficient (Ka): It is the ratio of horizontal and vertical principal effective Stresses when a retaining wall moves away (by asmall amount) from the retained soil. Passive earth pressure coefficient (Kp): It is the ratio of horizontal and vertical principal effective stresses when a retaining wall is forced against a soil mass. Coefficient of earth pressure at rest (Ko): It is the ratio of horizontal and vertical principal effective stresses when the retaining wall does not move at all, i.e. it is “at rest”. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 8
- 9. LATERAL EARTH PRESSURE – BASIC CONCEPTS We will consider the lateral pressure on a vertical wall that retains soil on one side. First, we will consider a drained case, i.e. The shear strength of the soil is governed by its angle of friction φ. In addition, we will make the following assumptions: – The interface between the wall and the soil is frictionless. – The soil surface is horizontal and there are no shear stresses on horizontal and vertical planes, i.e. The horizontal and vertical stresses are principal stresses. – The wall is rigid and extends to an infinite depth in a dry, homogenous, isotropic soil mass. – The soil is loose and initially in an at-rest state. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 9
- 10. LATERAL EARTH PRESSURE THEORY There are two classical earth pressure theories. They are 1. Coulomb's earth pressure theory. 2. Rankine's earth pressure theory. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 10
- 11. THE RANKINE THEORY ASSUMES: There is no adhesion or friction between the wall and soil Lateral pressure is limited to vertical walls Failure (in the backfill) occurs as a sliding wedge along an assumed failure plane defined by φ. Lateral pressure varies linearly with depth and the resultant pressure is located one-third of the height (H) above the base of the wall. The resultant force is parallel to the backfill surface. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 11
- 12. THE COULOMB THEORY IS SIMILAR TO RANKINE EXCEPT THAT: There is friction between the wall and soil and takes this into account by using a soil-wall friction angle of δ. Note that δ ranges from φ/2 to 2φ/3 and δ = 2φ/3 is commonly used. Lateral pressure is not limited to vertical walls The resultant force is not necessarily parallel to the backfill surface because of the soil-wall friction value δ. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 12
- 13. LATERAL EARTH PRESSURE FOR AT REST CONDITION If the wall is rigid and does not move with the pressure exerted on the wall, the soil behind the wall will be in a state of elastic equilibrium. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 13
- 14. LATERAL EARTH PRESSURE FOR AT REST CONDITION Element E is subjected to the following pressures. E Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 14
- 15. LATERAL EARTH PRESSURE FOR AT REST CONDITION If we consider the backfill is homogeneous then v and h both increase linearly with depth z. In such a case, the ratio of h to v remains constant with respect to depth, that is Where, Ko is called the coefficient of earth pressure for the at rest condition or at rest earth pressure Coefficient. The lateral earth pressure h acting on the wall at any depth z may be expressed as Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 15
- 16. LATERAL EARTH PRESSURE FOR AT REST CONDITION Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 16
- 17. COEFFICIENTS OF EARTH PRESSURE FOR AT REST CONDITION : KO Type of soil Ip Ko Loose sand, saturated 0.46 Dense sand, saturated 0.36 Dense sand, dry (e = 0.6) 0.49 Loose sand, dry (e = 0.8) 0.64 Compacted clay 9 0.42 Compacted clay 31 0.60 Organic silty clay, undisturbed (w{ = 74%) 45 0.57 Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 17
- 18. FACTORS AFFECTING KO The value of Ko depends upon the relative density of the sand and the process by which the deposit was formed. If this process does not involve artificial tamping the value of Ko ranges from about 0.40 for loose sand to 0.6 for dense sand. Tamping the layers may increase it to 0.8. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 18
- 19. DEVELOPMENT OF ACTIVE AND PASSIVE EARTH PRESSURES Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 19
- 20. HORIZONTAL STRESS AS A FUNCTION OF THE DISPLACEMENT Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 20
- 21. DEVELOPMENT OF EARTH PRESSURES Active Pressures ◦ Overburden (σ1) Driving Passive Pressures ◦ Wall (σ3) Driving Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 21
- 22. ACTIVE EARTH PRESSURE ‐ Wall moves away from soil Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 22
- 26. MOVEMENT REQUIRED TO DEVELOP ACTIVE EARTH PRESSURE Soil Type & Condition H Required Sands , Granular soil Dense 0.001 H to 0.002H loose 0.002 H to 0.004 H Clays Stiff/Hard 0.01H to 0.02 H Soft material 0.02 H to 0.05H H H Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 26
- 27. RANKINE'S EARTH PRESSURE THEORIES Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 27
- 28. RANKINE'S CONDITION FOR ACTIVE AND PASSIVE FAILURES IN A SEMI-INFINITE MASS OF COHESIONLESS SOIL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 28
- 30. RANKINE’S THEORY: ACTIVE EARTH PRESSURE Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 30
- 31. SMOOTH VERTICAL WALL WITH COHESIONLESS BACKFILL Backfill Horizontal-Active Earth Pressure Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 31
- 32. Backfill Horizontal-Passive Earth Pressure Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 32
- 33. RANKINE’S THEORY: PASSIVE EARTH PRESSURE Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 33
- 34. Relationship between Kp and KA Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 34
- 35. RANKINE’S THEORY: ACTIVE EARTH PRESSURE Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 35
- 36. TENSION CRACK IN SOIL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 36
- 37. RANKINE'S ACTIVE PRESSURE UNDER SUBMERGED CONDITION IN COHESION LESS SOIL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 37
- 38. RANKINE'S ACTIVE PRESSURE IN COHESIONLESS BACKFILL UNDER PARTLY SUBMERGED CONDITION WITH SURCHARGE LOAD Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 38
- 39. RANKINE'S ACTIVE PRESSURE FOR A SLOPING COHESIONLESS BACKFILL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 39
- 41. RANKINE'S PASSIVE PRESSURE IN SLOPING COHESIONLESS BACKFILL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 41
- 42. RANKINE'S ACTIVE EARTH RESSURE WITH COHESIVE BACKFILL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 42
- 43. RANKINE'S ACTIVE EARTH RESSURE WITH COHESIVE BACKFILL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 43
- 44. ACTIVE EARTH PRESSURE ON VERTICAL SECTIONS IN COHESIVE SOILS Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 44
- 45. EFFECT OF WATER TABLE ON LATERAL EARTH PRESSURE NΦ = tan2 (45+Φ/2) Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 45
- 46. RANKINE’S THEORY: SPECIAL CASES σh = K aσv ′ + u σv‘= σv-u u= pore water pressure Submergence: Inclined Backfill: Inclined but Smooth Back face of wall: Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 46
- 47. COULOMB'S EARTH PRESSURE THEORY Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 47
- 48. COULOMB'S EARTH PRESSURE THEORY FOR SAND FOR ACTIVE STATE Coulomb made the following assumptions in the development of his theory: 1. The soil is isotropic and homogeneous 2. The rupture surface is a plane surface 3. The failure wedge is a rigid body 4. The pressure surface is a plane surface 5. There is wall friction on the pressure surface 6. Failure is two-dimensional and 7. The soil is cohesionless Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 48
- 49. CONDITIONS FOR FAILURE UNDER ACTIVE CONDITIONS Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 49
- 50. PROCEDURE TO DRAW ABC 1. AB is the pressure face 2. The backfill surface BE is a plane inclined at an angle with the horizontal 3. is the angle made by the pressure face AB with the horizontal 4. H is the height of the wall 5. AC is the assumed rupture plane surface, and 6. is the angle made by the surface AC with the horizontal 7. W = yA, where A = area of wedge ABC Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 50
- 51. ACTIVE EARTH PRESSURE AND CO-EFFICICIENT Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 51
- 52. COULOMB'S EARTH PRESSURE THEORY FOR SAND FOR PASSIVE STATE Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 52
- 53. COULOMB’S THEORY: PASSIVE EARTH PRESSURE ( GRAPHICAL METHOD) Wall Friction: Coulomb’s theory overestimates Passive EP Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 53
- 54. COULOMB’S THEORY: ACTIVE EARTH PRESSURE ( GRAPHICAL METHOD) Wall Friction: Coulomb’s theory underestimates Active EP Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 54
- 56. CULMANN’S GRAPHICAL METHOD: ACTIVE EP Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 56
- 57. CULMANN’S GRAPHICAL METHOD: PASSIVE EP Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 57
- 58. PRESSURE DISTRIBUTION FOR STRATIFIED SOILS Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 58
- 59. THE LOCATION OF STRUTS AFFECTS THE VALUES AND DISTRIBUTIONS OF LATERAL EARTH PRESSURES Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 59
- 60. MODES OF GEOTECHNICAL FAILURES Sliding Overturning Bearing Overall Stability Settlement Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 60
- 61. LATERAL SUPPORT Gravity Retaining wall Soil nailing Reinforced earth wall Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 61
- 65. THE MAGNITUDE OF LATERAL EARTH PRESSURE DEPENDS ON: Shear strength characteristics of soil 2. Lateral strain condition 3. Pore water pressure 4. State of Equilibrium of soil 5. Wall and ground surface shape Previous conditions depends mainly on: a) Drainage conditions b) Interaction between soil and wall Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 65
- 66. CRITICAL COMMENTS ON EARTH PRESSURE THEORIES: Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 66
- 67. STAGE WISE CONSTRUCTION AND POROUS MATERIAL AS BACKFILL Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 67
- 69. WALL DRAINAGE Accumulation of rain water in the back fill results in its saturation, and thus a considerable increase in the earth pressure acting on the wall. This may eventually lead to unstable conditions. Two of the options to take care of this problem are the following: • Provision of weep holes w/o geo-textile on the back-face of wall • Perforated pipe draining system with filter Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 69
- 70. WALL DRAINAGE Weep Holes: They should have a minimum diameter of 10 cm and be adequately spaced depending on the backfill material. Geotextile material or a thin layer of some other filter may be used on the back face of wall for the full height in order to avoid the back fill material entering the weep holes and eventually clogging them. Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 70
- 73. REFERANCES: 1. Soil Mecahnics & Foundation Engg. - B.C.Punamia. 2. Soil Mechanics – V.N.S.Murthy 3. www.wikipedia.com Earth Pressure, SPP_CL, DoCL, DDU- Nadiad 73