Cement Stabilization of Soft Soil Subgrade

Abstract

The Kathmandu valley consist of vast network of road of length more than 2000 km. These road in many places transverse the soft soil deposits of Kathmandu valley. The rutting problem has excessively affected the serviceability conditions of these roads and require frequent maintenance to keep them serviceable. This study reviewed the stabilization of soft soil subgrade by cement. The sample of soil was collected from the depth around existing subgrade. Series of laboratory test showed that the soil was incompetent for subgrade layer and could suffer from subgrade rutting. Then, soil was stabilized with cement and series of laboratory test run on stabilized soil sample showed an improvement in the desirable properties of soil. CBR and UCS showed significant improvement with cement content and with increasing curing time. Optimum cement content was also determined for soil sample under study. Analysis and design of road using CSS and capping layer was done in Kenlayer to determine final design cross section of road using failure criteria given by AI method. The output of analysis showed that the thickness of pavement using CSS was significantly reduced as compared to pavement using capping layer. The study also found that the cost of road using CSS was cheaper for higher traffic intensity. The use of cement stabilization can be a cheaper option to deal with soft soil subgrade problems even though it was expensive for lower traffic intensity. The study also found that the cement stabilized road subgrade can have favorable impacts on national economy through reduction of use of bitumen surface course.