Performance of horizontal drains in residual soil slope.

Abstract

In tropical and subtropical regions, shallow landslides often occur in residual soil slopes. Short-duration, high-intensity rainfall will increase the pore-water pressure. As a result, the shear strength of the soil in the slopes decreases and the stability of the slopes is affected. In this study, horizontal drains were installed in a residual soil slope in Singapore in order to improve the stability of the slope. The slope was instrumented with tensiometers and piezometers to investigate the effectiveness of the horizontal drains as a slope stabilization method against rainfall-induced slope failures. The variations in water table elevation and matric suction in the slope due to rainfall events were monitored. In addition, numerical analyses of the seepage into the slope brought about by the rainfall were carried out, and the results showed a reasonably good agreement with the data obtained from field measurements. The field measurement results indicated that horizontal drains were indeed effective for lowering the water table and for increasing the stability of the investigated slope. Therefore, horizontal drains are considered to be a useful and economical method for improving the stability of residual soil slopes against rainfall.