7
tailings dam when gradual impoundment over time reduces
the factor of safety of the embankment
Another experiment was conducted to ascertain the
stability of a slope with the presence of groundwater.
In this experiment, water level was kept constant in
the bottom chamber and seepage allowed from the upslope
tank downslope. The pressure from the upslope tank into
the bottom chamber creates an uplift force downslope
which contributes to the instability of the slope. Firstly, the
toe becomes very unstable and loose and forces the crest to
slide. The flow vectors see such forces in the groundwater
model where the uplift force moves from the bottom cham-
ber to the toe. The steady-state analysis showed a factor of
safety of 1.32 and 0.715 before and after failure, respec-
tively (Figure 12).
It can be concluded from the images that the presence
of water and the increase in pore pressure contributes sig-
nificantly to the stability of the slope.
4.4 Experiment for seepage front (Steady-state and
Transient)
Seepage is a complex phenomenon in soil mechanics. A
seepage front migrates throughout a slope when the soil
particles come into contact with water. Water moves from
(a) Before failure
(b) After failure
Figure 10. Experiment of gradual water rise (a) before failure
(b) after failure
(a) The factor of safety at 3 minutes
(b) The factor of safety at 6 minutes
(c) The factor of safety at the failure at 9 minutes
Figure 11. Factor of safety of slopes with time