Stabilization of cut slopes in highways by surface drainage and vegetation

Abstract

At number of locations in Sri Lanka, deep cuts were made in natural slopes for the construction ' of expressways. These slopes are made of residual soil and the parent rock is metamorphic. In most cases the v ground water table is low and significant matric suctions prevail in the soil during dry periods of weather. - With the infiltration of rainwater, the matric suction will be lost and even perched water table conditions could be developed. The presence uf surface protecting vegetation and drainage measures such as berm drains will reduce the infiltration. Deep roots present will provide a nailing effect. This behavior was studied by modeling the process by Geoslope SEEP/W programme. Stability of the slope was assessed by the SLOPE/W after incorporating the changes in the pore pressure regime. The results of the study illustrated the effectiveness of surface protecting vegetation and deep roots in maintain reasonable safety margins in the slope during periods of heavy rain.