Control Of Ground Water For Slope Stability By Trenching Method

Slope failure can be defined as the slope that collapses due to weakened self-retaining
ability of the earth under the certain influence such as rainfall, earthquake and behavior
of soil itself. Slope movement depends on two main factors which are slope steepness
and slope stability. Many slope failures have taken up during or after a period of rain and
its can be concluded that rainfall is the main cause of slope failure. This report presents
the results from site investigations and soil tests carried out at the campus of Universiti
Teknologi PETRONAS (UTP), where a landsliding had occurred behind building 13.
Experiment for soil characteristics was conducted in the laboratory and a model on the
influence of rising groundwater level towards the slope stability was designed and tested.
The model used was a rectangular tank with dimensions of I in length of 0.5 in and width
of 0.4 m deep. The slope angle was about 33° representing angle of a cut slope. PVC pipe
was used as a trench and also for standpipe reading. Different water level was used to
bring about different groundwater level that might occur on site. The influence of
different water level of groundwater was examined by determining the moisture content
of the soil as well as the level of water in the standpipe. It was found that the presence of
the Trench reduces the level of moisture on the soil even when the height of the
groundwater table is at the same level as the soil. The moisture content was always below
24% above the trench while the soil below the trench reached the liquid limit of about
42%. This results differs from those recorded earlier from previous studies done without
the trench provided, from their results it was obtained that as water level become higher
than the toe the moisture of the soil increased to the liquid limit level this may cause
slope failure.