Module 2 : Theory of Earth Pressure and Bearing Capacity
Lecture 6 : Introduction[ Section 6.2 Displacement Related Earth Pressure]
The following Table 2.2 shows a typical calculation. In the full mobilization case, at the base , so = at the base and at the top = 0 0. The correction factor at the base is therefore (40.4/71.47)=0.565, and at the top it is zero. By assuming a linear variation of correction factor from the top, the calculated values of are corrected as shown in table For other cases with , the correction factor of 0.565 obtained at the base for the case of is maintained, with again a linear variation from zero at the top.
Some ill-points very near to the ground are neglected by considering that experimental errors may have been caused due to some arching action near ground as also mentioned by experimentalists in their papers.
Table 2.2 :Typical calculation to obtain mobilized friction angle in RT mode and with (Data from Fang et al, 1986),
Depth z in m
Horizontal acticve earth pressure in kN/m 2
values
Calculated
(Degrees)
Z/D values
Corrected
(Degrees)
0
0
-
-
0
0
0
-
0.153
4.790
1.951
-
0.15
-
0.15
-
0.305
1.294
0.263
32.54
0.3
23.12
0.3
1.91
0.467
1.444
0.192
39.50
0.46
25.22
0.46
1.36
0.628
1.87
0.185
40.32
0.62
21.1
0.62
0.84
0.793
1.583
0.124
48.51
0.78
24.25
0.78
0.77
0.958
0.766
0.05
63.32
0.94
34.02
0.94
0.9
1.016
0.298
0.018
71.47
1.00
40.40
1.00
1.00
The proposed equation as a lower bound is given by,
-------(1)
and eq(1) is valid for 0<x<=1 and 0< <1. However at depth z=0, for any value of , active earth pressure will be zero (ground surface).
, so 
= 
at the base and at the top 
, the correction factor of 0.565 obtained at the base for the case of 
is maintained, with again a linear variation from zero at the top. 
and 
with 
(Data from Fang et al, 1986), 
in kN/m 2
values 
<1. However at depth z=0, for any value of 
, active earth pressure will be zero (ground surface). 
