Geotechnical Engineering

DHARM

COMPRESSIBILITY AND CONSOLIDATION OF SOILS 233

u 0

2H

u 2

u 1 u 3 u 1 u 2

u=ui 0

I(a) I(b)

u = u + u ———i 12 H–zH

II

u = u sin ——i (^3) 2Hpz u = u + u ——— – u sin ——i 12 H–zH 3 p
z
2H
III
0
10
20
30
40
50
60
70
80
90
Average consolidation U% 100
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Time factor, T
T = 0.008
II
I
III
Cases of double
drainage with
different distributions
of initial excess
hydrostatic
pressure
with depth
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
I
0.008
0.031
0.071
0.126
0.197
0.287
0.403
0.567
0.848
II
0.048
0.090
0.115
0.207
0.281
0.371
0.488
0.652
0.933
U T
u 3
Fig. 7.24 Average degree of consolidation versus time factor (After Taylor, 1948)
If the hydrostatic excess pressure is constant throughout the depth, the solution for the
single drainage conditions will be the same as that for the corresponding double drainage case;
that is to say, curve I of Fig. 7.24 will apply. For other distributions of hydrostatic excess
pressure, the results will be different. For triangular distributions of hydrostatic excess pres-
sure indicated in Fig. 7.25, the values of the time factor for different degrees of consolidation
are shown:
u=i Ds Impervious
Pervious
u=i Ds
Impervious
Pervious 0.10.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
(a)
0.050
0.102
0.158
0.221
0.294
0.383
0.500
0.685
0.940
U T
(b)
0.003
0.009
0.024
0.049
0.092
0.166
0.272
0.440
0.720
(a) Minimum pressure
near drainage face
(b) Maximum pressure
near drainage face
(c) Values of time factor for
different degrees of consolidation
Fig. 7.25 Single drainage condition—triangular distributions
of initial hydrostatic excess pressure