Instrumentation of an unsaturated residual soil slope

The stability of slopes has become a major concern in areas that experience frequent periods of heavy rainfall such as the tropical areas of Southeast Asia. Previous research has indicated that rainfall has a detrimental effe ct on the stability of residual soil slopes. The reason for this is that th e additional shear strength that exists in unsaturated soils due to negativ e pore-water pressures is lost as a result of rainwater infiltration into t he soil. To study the infiltration characteristics in slopes, a residual soil slope in Singapore was:instrumented. The instruments were used to determine the c hanges in the pore-water pressure distribution throughout the slope in resp onse to evaporation and infiltration. Tensiometers were used to measure neg ative pore-water pressures, piezometers were used to measure the groundwate r level, and a rain gage was used to measure rainfall intensifies on the sl ope; An automated data acquisition system was used to collect the data from the slope. This paper describes the instrumentation program and the proced ures associated with the installation of the instruments into the slope. Ty pical measurement data collected from the slope are presented, and their in terpretations are discussed.