Instrumentation and matric suction measurement in a decomposed granite soil slope

A field instrumentation program was carried out to measure the matric suction in a granite residual soil slope. The variation in matric suction due to changes in climatic condition was investigated to study its effect on slope stability. Matric suction in the soil increased during dry periods and decreased during wet periods. Maximum change in matric suction occurred near the ground surface and the magnitude of matric suction change decreased with depth. The amount of decrease in matric suction after a rainfall was observed to be a function of the initial matric suction just prior to the rainfall. Large variations in matric suction near the ground surface due to evaporation and infiltration processes would result in changes in shear strength of the soil. As a result, the stability of the slope also changes with the change in matric suction. Effect of matric suction on the slope stability is also investigated and discuss