Module 2 : Theory of Earth Pressure and Bearing Capacity
Lecture 6 : Introduction[ Section 6.2 Displacement Related Earth Pressure]
III
Rotation about the bottom (RB)
Consider Fig.2.5 (c), a rigid retaining wall of height D, rotating about the bottom and the horizontal displacement at top is given by , Let,
----------(2)
and assuming linear variation with depth,
----------(3)
----------(4)
Table 2.3 : Typical calculation to obtain mobilized friction angle in RB mode and with (Data from Fang et al, 1986),
Depth z in m
Horizontal acticve earth pressure in kN/m 2
values
Calculated
(Degrees)
1-Z/D values
Corrected
(Degrees)
0
0
-
36.3
1.00
35.00
0.00
-
0.153
0.559
0.237
34.39
0.83
27.55
0.17
4.72
0.302
1.331
0.284
30.10
0.67
17.82
0.33
1.54
0.467
1.663
0.23
34.98
0.49
16.72
0.51
0.94
0.628
2.461
0.253
32.93
0.31
8.79
0.69
0.37
0.793
2.994
0.244
33.76
0.13
3.63
0.87
0.12
0.915
3.326
0.235
34.57
0.00
0.00
1.00
0.00
Table 2.3 shows a typical calculation. In the full mobilization case at top = at the top and at the base = 0 0. Considering this criteria, correction has been made using a correction factor of (35/36.3) at the top. Corrected values are shown in table 2.3. For other cases with , the same maximum correction factor is applied at top to a linear variation of zero at the base.
The proposed equation as a lower bound to the points is given by,
--------(5)
And Eq.(5) is valid for 0<X<=1 and not equal to zero.
, Let, 
and 
with 
(Data from Fang et al, 1986), 
in kN/m 2
values 
at the top and at the base 
, the same maximum correction factor is applied at top to a linear variation of zero at the base. 
not equal to zero. 
