PENGARUH PERUBAHAN MUKA AIR TANAH DAN TERASERING TERHADAP PERUBAHAN KESTABILAN LERENG

Abstract

Drenched rain soil is a cause in reduction of the soil strength in line with
increasing ground saturation. Reduction of this strength reduces the slope stability
which can cause sliding during the rainy season. Research was conducted by
carrying out simulations on slopes using a Stable 2004 Program on different slope
geometries, number of terraces and soil properties. The effects of drenched rain soil
were simulated by changing ground water levels. The effects of slope geometries
including inclination and height of slopes and earthquake loads were considered in
the analyses. To ease the analyses, the terraces were grouped into 4 which were T1,
T2, T3, and T4 having 1, 2, 3 and 4 terraces respectively. The slope without terrace
is referred as T0, the slope inclination changed from 1:1 to 1:2 and 1:3 with
different type of soils (clay, sand and variation of clay-sand). The analysis results
showed that the increase in ground water level resulted in the reduction of slope
stability for the slope of 1:1, 1:2, and 1:3, the safety factors increased with
increasing number of terraces and the highest was thus in T4. For Sandy slope of
1:1 with T1 terrace, the increase in safety factor was noticeable, while for T2, T3,
and T4 types they were almost the same. Sandy slopes of 1:2 and 1:3 with terraces
changing from T1 to T4 causes the average safety factor increase in slightly. Clay
slope with earthquake loads of 0.25 g and 0.45 g gave the average reduction in
safety factor of 43% and 55% respectively. The earthquake loads of 0.25 g and 0.45 g caused reductions on safety factors of sandy slopes by 50% and 70%
respectively.