LATERAL EARTH PRESSURE PARAMETERS
Cohesive Soil
(Non-Expansive Clay)
Condition
Cohesionless Soil
(Granular - Sand)
Assumed Backfill Characteristics
Approx Total Density
140
Approximate Friction Angle
15º - 20º
15
0.54
0.70
1.87
0.59
Active Pressure Coefficient, Ka =
(1-sinϕ) / (1+sinϕ) = 1/Kp
At-Rest Pressure Coefficient, Ko =
(1-sinϕ)
Passive Pressure Coefficient, Kp =
(1+sinϕ) / (1-sinϕ) = 1/Ka
Active Drained
Active Undrained
At-Rest Drained
At Rest Undrained
Passive Drained
Passive Undrained
Active
At-Rest
Passive
140
pcf
Ka, Ko, Kp Averages
20
pcf
30
30º - 35º
Ka, Ko, Kp Averages
35
0.30
0.27
0.46
0.43
3.35
3.69
0.33
0.30
0.74
0.70
0.66
0.50
0.46
1.70
1.87
2.04
3.00
3.35
Estimated Lateral Earth Pressures (Equivalent Fluid Pressures)
76
104
98
117
262
145
0.54
pcf Ka(γ) =
0.54(140) = 76 pcf
pcf Ka(γ - γw) + γw =
0.54(140 - 62.4) + 62.4 = 104 pcf
pcf Ko(γ) =
0.7(140) = 98 pcf
pcf Ko(γ - γw) + γw =
0.7(140 - 62.4) + 62.4 = 117 pcf
pcf Kp(γ) =
1.87(140) = 262 pcf
pcf Kp(γ - γw) =
1.87(140 - 62.4) = 145 pcf
0.49
42
86
65
98
468
260
pcf Ka(γ) =
0.3(140) = 42 pcf
pcf Ka(γ - γw) + γw =
0.3(140 - 62.4) + 62.4 = 86 pcf
pcf Ko(γ) =
0.46(140) = 65 pcf
pcf Ko(γ - γw) + γw =
0.46(140 - 62.4) + 62.4 = 98 pcf
pcf Kp(γ) =
3.35(140) = 468 pcf
pcf Kp(γ - γw) =
3.35(140 - 62.4) = 260 pcf
R = (0.5)(Ko)(γ)(H ) = (0.5)(EFP)(H ) = psf / lineal foot of wall length
2
2
Cohesive Soil
(Non-Expansive Clay)
Condition
Cohesionless Soil
(Granular - Sand)
Assumed Backfill Characteristics
Approx Total Density
110
Approximate Friction Angle
15º - 20º
15
0.54
0.70
1.87
0.59
Active Pressure Coefficient, Ka =
(1-sinϕ) / (1+sinϕ) = 1/Kp
At-Rest Pressure Coefficient, Ko =
(1-sinϕ)
Passive Pressure Coefficient, Kp =
(1+sinϕ) / (1-sinϕ) = 1/Ka
Active Drained
Active Undrained
At-Rest Drained
At Rest Undrained
Passive Drained
Passive Undrained
Active
At-Rest
Passive
59
88
77
96
206
89
110
pcf
Ka, Ko, Kp Averages
20
pcf
30
30º - 35º
Ka, Ko, Kp Averages
35
0.30
0.27
0.46
0.43
3.35
3.69
0.33
0.30
0.74
0.70
0.66
0.50
0.46
1.70
1.87
2.04
3.00
3.35
Estimated Lateral Earth Pressures (Equivalent Fluid Pressures)
0.54
pcf Ka(γ) =
0.54(110) = 59 pcf
pcf Ka(γ - γw) + γw =
0.54(110 - 62.4) + 62.4 = 88 pcf
pcf Ko(γ) =
0.7(110) = 77 pcf
pcf Ko(γ - γw) + γw =
0.7(110 - 62.4) + 62.4 = 96 pcf
pcf Kp(γ) =
1.87(110) = 206 pcf
pcf Kp(γ - γw) =
1.87(110 - 62.4) = 89 pcf
0.49
33
77
51
84
368
159
pcf Ka(γ) =
0.3(110) = 33 pcf
pcf Ka(γ - γw) + γw =
0.3(110 - 62.4) + 62.4 = 77 pcf
pcf Ko(γ) =
0.46(110) = 51 pcf
pcf Ko(γ - γw) + γw =
0.46(110 - 62.4) + 62.4 = 84 pcf
pcf Kp(γ) =
3.35(110) = 368 pcf
pcf Kp(γ - γw) =
3.35(110 - 62.4) = 159 pcf
140
Rankine At-Rest, Ko
Lateral Earth Pressure Parameters
130
140 pcf-Undrained
120
130 pcf-Undrained
Equivalent Fluid Pressures (pcf)
110
Undrained Conditions
100
120 pcf-Undrained
90
80
110 pcf-Undrained
70
Low to Moderately Expansive Clays
Mixed Soils
←→
←→
Clean Sands and Gravels
60
140 pcf-Drained
50
130 pcf-Drained
Assumes:
No safety factor
Ignores adhesion or friction between the wall and soil
Lateral pressure is limited to vertical walls
No surcharge
Ignores cohesion shear strength
Failure (in the backfill) occurs as a sliding wedge along
an assumed failure plane defined by Ø
Lateral pressure varies linearly with depth and the
resultant pressure is located 1/3 of the height
above the base of the wall
40
30
20
10
Drained Conditions
120 pcf-Drained
110 pcf-Drained
0
0
5
10
15
20
25
30
35
40
45
Internal Friction Angle (degrees)
Lateral Earth Pressures - Table and Graphs.xlsx
9/11/2014