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Prof. S.P.PARMAR
DEPARTMENT OF CIVIL ENGINEERING
DHARMASINH DESAI UNIVERSITY, NADIAD
Mail: samirddu@gmail.com
1
WHERE EARTH PRESSURE?
 Calculating lateral earth pressure is
necessary in order to design structures such
as:
 Retaining...
TYPES OF RETAINING WALLS:
3
USE OF RETAINING WALLS
4
USE OF RETAINING WALLS
5
IN GEOTECHNICAL ENGINEERING,
IT IS OFTEN NECESSARY TO PREVENT LATERAL SOIL
MOVEMENTS
Cantilever
retaining wall
Braced exca...
DEFINITION OF KEY TERMS
 Active earth pressure coefficient (Ka): It is the
ratio of horizontal and vertical principal eff...
LATERAL EARTH PRESSURE – BASIC
CONCEPTS
 We will consider the lateral pressure on a vertical wall that
retains soil on on...
LATERAL EARTH PRESSURE THEORY
 There are two classical earth pressure theories.
They are
 1. Coulomb's earth pressure th...
THE RANKINE THEORY ASSUMES:
 There is no adhesion or friction between the wall
and soil
 Lateral pressure is limited to ...
THE COULOMB THEORY IS SIMILAR TO
RANKINE EXCEPT THAT:
 There is friction between the wall and soil and
takes this into ac...
LATERAL EARTH PRESSURE FOR AT
REST CONDITION
 If the wall is rigid and does not move with the
pressure exerted on the wal...
LATERAL EARTH PRESSURE FOR AT REST
CONDITION
Element E is subjected to the following pressures.
E
13
LATERAL EARTH PRESSURE FOR AT REST
CONDITION
 If we consider the backfill is homogeneous then v
and h both increase lin...
LATERAL EARTH PRESSURE FOR AT REST
CONDITION
15
COEFFICIENTS OF EARTH PRESSURE FOR AT
REST CONDITION : KO
Type of soil Ip Ko
Loose sand, saturated 0.46
Dense sand, satura...
FACTORS AFFECTING KO
 The value of Ko depends upon the relative
density of the sand and the process by
which the deposit ...
DEVELOPMENT OF ACTIVE AND PASSIVE
EARTH PRESSURES
18
HORIZONTAL STRESS AS A FUNCTION OF THE
DISPLACEMENT
19
DEVELOPMENT OF EARTH PRESSURES
Active Pressures
◦ Overburden (σ1)
Driving
Passive Pressures
◦ Wall (σ3) Driving
20
ACTIVE EARTH PRESSURE
 ‐ Wall moves away from soil
21
ACTIVE EARTH PRESSURE
22
PASSIVE EARTH PRESSURE
23
PASSIVE EARTH PRESSURE
24
MOVEMENT REQUIRED TO DEVELOP ACTIVE
EARTH PRESSURE
Soil Type & Condition H Required
Sands , Granular soil
Dense 0.001 H t...
RANKINE'S EARTH PRESSURE
THEORIES
26
RANKINE'S CONDITION FOR ACTIVE AND PASSIVE
FAILURES IN A SEMI-INFINITE MASS OF COHESIONLESS
SOIL
27
28
RANKINE’S THEORY: ACTIVE EARTH
PRESSURE
29
SMOOTH VERTICAL WALL WITH
COHESIONLESS BACKFILL
 Backfill Horizontal-Active Earth Pressure
30
 Backfill Horizontal-Passive Earth Pressure
31
RANKINE’S THEORY: PASSIVE EARTH
PRESSURE
32
 Relationship between Kp and KA
33
RANKINE’S THEORY: ACTIVE EARTH
PRESSURE
34
TENSION CRACK IN SOIL
35
RANKINE'S ACTIVE PRESSURE UNDER SUBMERGED
CONDITION IN COHESION LESS SOIL
36
RANKINE'S ACTIVE PRESSURE IN COHESIONLESS
BACKFILL UNDER PARTLY SUBMERGED CONDITION
WITH SURCHARGE LOAD
37
RANKINE'S ACTIVE PRESSURE FOR A SLOPING
COHESIONLESS BACKFILL
38
MOHR DIAGRAM
39
RANKINE'S PASSIVE PRESSURE IN SLOPING
COHESIONLESS BACKFILL
40
RANKINE'S ACTIVE EARTH RESSURE WITH
COHESIVE BACKFILL
41
RANKINE'S ACTIVE EARTH RESSURE WITH
COHESIVE BACKFILL
42
ACTIVE EARTH PRESSURE ON VERTICAL
SECTIONS IN COHESIVE SOILS
43
EFFECT OF WATER TABLE ON LATERAL EARTH
PRESSURE
NΦ = tan2 (45+Φ/2)
44
RANKINE’S THEORY: SPECIAL CASES
σh = K aσv ′ + u
σv‘= σv-u
u= pore water pressureSubmergence:
Inclined Backfill:
Inclined ...
COULOMB'S EARTH PRESSURE
THEORY
46
COULOMB'S EARTH PRESSURE THEORY FOR
SAND FOR ACTIVE STATE
 Coulomb made the following assumptions in
the development of h...
CONDITIONS FOR FAILURE UNDER ACTIVE
CONDITIONS
48
PROCEDURE TO DRAW  ABC
1. AB is the pressure face
2. The backfill surface BE is a plane inclined at an
angle  with the h...
ACTIVE EARTH PRESSURE
50
COULOMB'S EARTH PRESSURE THEORY FOR
SAND FOR PASSIVE STATE
51
COULOMB’S THEORY: PASSIVE EARTH
PRESSURE ( GRAPHICAL METHOD)
Wall Friction:
Coulomb’s
theory
overestimates
Passive EP
52
COULOMB’S THEORY: ACTIVE EARTH
PRESSURE ( GRAPHICAL METHOD)
Wall Friction:
Coulomb’s
theory
underestimates
Active EP
53
COULOMB’S THEORY: SOLUTIONS
54
CULMANN’S GRAPHICAL METHOD: ACTIVE EP
55
CULMANN’S GRAPHICAL METHOD: PASSIVE EP
56
PRESSURE DISTRIBUTION FOR STRATIFIED
SOILS
57
THE LOCATION OF STRUTS AFFECTS THE VALUES AND
DISTRIBUTIONS OF LATERAL EARTH PRESSURES
58
MODES OF GEOTECHNICAL FAILURES
Sliding Overturning
Bearing
Overall Stability Settlement
59
LATERAL SUPPORT
Gravity Retaining
wall
Soil nailing Reinforced earth wall
60
SOIL NAILING
61
62
SHEET PILE
THE MAGNITUDE OF LATERAL EARTH
PRESSURE DEPENDS ON:
 Shear strength characteristics of soil
 2. Lateral strain condition...
64
WALL DRAINAGE
Accumulation of rain water in the back fill results in its
saturation, and thus a considerable increase in t...
WALL DRAINAGE
Weep Holes: They should have a
minimum
diameter of 10 cm and be adequately
spaced depending on the backfill ...
GABION RETAINING WALL
67
REFERANCES:
1. Soil Mecahnics & Foundation Engg. - Arora.
2. Soil Mechanics – V.N.S.Murthy
3. www.wikipedia.com
68
69
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Earth pressure 14 2-2012

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Earth pressure 14 2-2012

  1. 1. Prof. S.P.PARMAR DEPARTMENT OF CIVIL ENGINEERING DHARMASINH DESAI UNIVERSITY, NADIAD Mail: samirddu@gmail.com 1
  2. 2. 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 2
  3. 3. TYPES OF RETAINING WALLS: 3
  4. 4. USE OF RETAINING WALLS 4
  5. 5. USE OF RETAINING WALLS 5
  6. 6. IN GEOTECHNICAL ENGINEERING, IT IS OFTEN NECESSARY TO PREVENT LATERAL SOIL MOVEMENTS Cantilever retaining wall Braced excavation Anchored sheet pile 6
  7. 7. 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 a small 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”. 7
  8. 8. 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. 8
  9. 9. 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. 9
  10. 10. 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. 10
  11. 11. 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. 11
  12. 12. 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. 12
  13. 13. LATERAL EARTH PRESSURE FOR AT REST CONDITION Element E is subjected to the following pressures. E 13
  14. 14. 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 14
  15. 15. LATERAL EARTH PRESSURE FOR AT REST CONDITION 15
  16. 16. 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 16
  17. 17. 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. 17
  18. 18. DEVELOPMENT OF ACTIVE AND PASSIVE EARTH PRESSURES 18
  19. 19. HORIZONTAL STRESS AS A FUNCTION OF THE DISPLACEMENT 19
  20. 20. DEVELOPMENT OF EARTH PRESSURES Active Pressures ◦ Overburden (σ1) Driving Passive Pressures ◦ Wall (σ3) Driving 20
  21. 21. ACTIVE EARTH PRESSURE  ‐ Wall moves away from soil 21
  22. 22. ACTIVE EARTH PRESSURE 22
  23. 23. PASSIVE EARTH PRESSURE 23
  24. 24. PASSIVE EARTH PRESSURE 24
  25. 25. 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 25
  26. 26. RANKINE'S EARTH PRESSURE THEORIES 26
  27. 27. RANKINE'S CONDITION FOR ACTIVE AND PASSIVE FAILURES IN A SEMI-INFINITE MASS OF COHESIONLESS SOIL 27
  28. 28. 28
  29. 29. RANKINE’S THEORY: ACTIVE EARTH PRESSURE 29
  30. 30. SMOOTH VERTICAL WALL WITH COHESIONLESS BACKFILL  Backfill Horizontal-Active Earth Pressure 30
  31. 31.  Backfill Horizontal-Passive Earth Pressure 31
  32. 32. RANKINE’S THEORY: PASSIVE EARTH PRESSURE 32
  33. 33.  Relationship between Kp and KA 33
  34. 34. RANKINE’S THEORY: ACTIVE EARTH PRESSURE 34
  35. 35. TENSION CRACK IN SOIL 35
  36. 36. RANKINE'S ACTIVE PRESSURE UNDER SUBMERGED CONDITION IN COHESION LESS SOIL 36
  37. 37. RANKINE'S ACTIVE PRESSURE IN COHESIONLESS BACKFILL UNDER PARTLY SUBMERGED CONDITION WITH SURCHARGE LOAD 37
  38. 38. RANKINE'S ACTIVE PRESSURE FOR A SLOPING COHESIONLESS BACKFILL 38
  39. 39. MOHR DIAGRAM 39
  40. 40. RANKINE'S PASSIVE PRESSURE IN SLOPING COHESIONLESS BACKFILL 40
  41. 41. RANKINE'S ACTIVE EARTH RESSURE WITH COHESIVE BACKFILL 41
  42. 42. RANKINE'S ACTIVE EARTH RESSURE WITH COHESIVE BACKFILL 42
  43. 43. ACTIVE EARTH PRESSURE ON VERTICAL SECTIONS IN COHESIVE SOILS 43
  44. 44. EFFECT OF WATER TABLE ON LATERAL EARTH PRESSURE NΦ = tan2 (45+Φ/2) 44
  45. 45. RANKINE’S THEORY: SPECIAL CASES σh = K aσv ′ + u σv‘= σv-u u= pore water pressureSubmergence: Inclined Backfill: Inclined but Smooth Back face of wall: 45
  46. 46. COULOMB'S EARTH PRESSURE THEORY 46
  47. 47. 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 47
  48. 48. CONDITIONS FOR FAILURE UNDER ACTIVE CONDITIONS 48
  49. 49. 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 49
  50. 50. ACTIVE EARTH PRESSURE 50
  51. 51. COULOMB'S EARTH PRESSURE THEORY FOR SAND FOR PASSIVE STATE 51
  52. 52. COULOMB’S THEORY: PASSIVE EARTH PRESSURE ( GRAPHICAL METHOD) Wall Friction: Coulomb’s theory overestimates Passive EP 52
  53. 53. COULOMB’S THEORY: ACTIVE EARTH PRESSURE ( GRAPHICAL METHOD) Wall Friction: Coulomb’s theory underestimates Active EP 53
  54. 54. COULOMB’S THEORY: SOLUTIONS 54
  55. 55. CULMANN’S GRAPHICAL METHOD: ACTIVE EP 55
  56. 56. CULMANN’S GRAPHICAL METHOD: PASSIVE EP 56
  57. 57. PRESSURE DISTRIBUTION FOR STRATIFIED SOILS 57
  58. 58. THE LOCATION OF STRUTS AFFECTS THE VALUES AND DISTRIBUTIONS OF LATERAL EARTH PRESSURES 58
  59. 59. MODES OF GEOTECHNICAL FAILURES Sliding Overturning Bearing Overall Stability Settlement 59
  60. 60. LATERAL SUPPORT Gravity Retaining wall Soil nailing Reinforced earth wall 60
  61. 61. SOIL NAILING 61
  62. 62. 62 SHEET PILE
  63. 63. 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 63
  64. 64. 64
  65. 65. 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 65
  66. 66. 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. 66
  67. 67. GABION RETAINING WALL 67
  68. 68. REFERANCES: 1. Soil Mecahnics & Foundation Engg. - Arora. 2. Soil Mechanics – V.N.S.Murthy 3. www.wikipedia.com 68
  69. 69. 69

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