Consolidation and Swelling Processes in Unsaturated Soils - Unsaturated Soil Mechanics in Engineering Practice - page 837

steady-state conditions after about 150 days. The total amount
of water that leaked from the water line with time is presented
in Fig. 16.31. A loss of 35 m 3 of water is equivalent to about
3.5 m 3 of water over each meter of width of the floor. This
amount of water is more than the amount of water required
for steady-state conditions to be attained under the specified
boundary conditions.
Figure 16.32 presents pore-water pressure profiles under
the center of the slab for various times and also for the case
where the final pore-water pressure goes to zero and then a
hydrostatic condition. Figure 16.33 shows the matric suction
distribution in the soil at steady-state conditions. The matric
suction at steady-state conditions is about 20 kPa under the
center of the slab.
Figure 16.34 shows contours of vertical displacements due
to loading. Less than 1mm of settlement is predicted due to
the loading at the center of the slab. The induced net normal
stress was used to calculate the final net normal stress state
in the soil. The soil was loaded with an initial net normal
stress and field matric suctions estimated from the oedometer
tests. The sum of the initial net normal stress and the initial
matric suction equivalent was used along with the swelling
index for the prediction of displacements and stress states.

e

Final stress state

Initial stress state

Wetting

Loading

Matric suction

Net normal stress

Figure 16.28 Stress path followed in swelling of soil (i.e., stress
state versus deformation path).

A parametric study was undertaken to assess the effect of
varying numerous input variables to the analysis.
Figure 16.30 presents changes of matric suction with time
at various points in the soil. Matric suctions decreased sig-
nificantly during the first 30 days of wetting and approached

15 kN/m 15 kN/m

5.76 kPa

0

Concrete slab

A B C

1

2

0 5 10 15 20

Distance (m)

Figure 16.29 Boundary conditions for stress state versus deformation analysis.

600

AB C

400

C

A

200

B

0

0 50 100 150

Time (days)

Figure 16.30 Matric suction changes with time for various points in soil mass.