Therefore in this paper we will present the stability analysis carried out on the
Dwesat dam with vertical core, its high is 33m, the downstream slope of 1V:2.75H and the
upstream slope of 1V:3.0H. Thickness of the vertical core was varied from 1V:
0.25H to
1V:2.0H, and also present the effect of the varied thickness on slope stability for both
upstream and downstream under three design conditions i.e. during and end of
construction, steady state seepage and rapid draw down by General Limit Equilibrium
Method using GeoStudio software.
It was observed from the analysis that by varying the thickness of vertical core of
earth dam, thinner core up to 1V:1.30H gives more stability and further increase in
thickness of core tends to sharp decline in factor of safety for both upstream and
downstream slope under different design conditions.
The stability of the upstream shell of the dams is changed under the rapid drawdown
condition where the pore water pressure has a different values according to the soil
permeability. This paper considers the stability of the upstream shell of the "
Braddon" dam
with many types of soil and analyses each type under two rapid drawdown programs, the
first program is when the discharge happens, according to the irrigation outlet by 25 m3/s,
and the second program is when the discharge happens according to the tunnel conversion
of the river by 500 m3/s. The obtained results show, that the stability of the upper slope
under considered boundary conditions changed according to the soil type. Some soil have
good stability factor while other soil collapsed .Accordingly, we can conclude that the
type of soil of the upper dam slope is important and we could chose the appropriate type
which does not cause dangerous during the rapid drawdown. Also the study shows that:
the highest values of the safety factors result when the slopes are formed of high
permeability soils as well as the slopes of homogeneous soil, while the soils formed of
materials between them appeared decreasing values of safety factors.
