Integrated approach in studying rock and soil slope stability in a tropical and active tectonic country

An integrated study on slope stability has been conducted in the high weathering zone of the tropical and active tectonic country, Indonesia. The research aims to introduce an integrated and comprehensive approach in studying the soil and rock slope stability. Geophysical methods, including two seismic refraction tomography (SRT) and electrical resistivity tomography (ERT) lines, were deployed to determine the slip zone of the landslide. Slope kinematic analysis and rock mass classification were performed on the slope surface for obtaining data of engineering geology combined with Standard Penetration Test (SPT) data collected next to the sloping road. The soil slope stability analysis was simulated by employing the Slope/W software to determine the factor of safety. The geophysical methods revealed three layers of rock and soil on top of the rock layer, showing the slip zone of the landslide. The kinematic analysis revealed the planar failure, which possibly occurred in Site B of Babarot—Gayo Lues road in Aceh Province due to the parallelism between slope and joint. The integrated data from the geophysical methods and in situ RMR indicate that the rock mass classification in sub-surface is classified as Very Good and Good Rock. It appears to be stable. The soil above the slope in sites A and B has 1.058 and 1.182 factor of safety, respectively; yet, it has less than 0.847, the factor of safety, when loaded by the earthquake and it is unstable.