Kinematic Analysis and Rock Mass Classifications for Rock Slope Failure at USAID Highways

Abstract

Rock slope kinematic analysis and rock mass classifications has been conducted at the 17^th km to 26^th km of USAID (United States Agency for International Development) highway in Indonesia. This research aimed to examine the type of rock slope failures and the quality of rock mass as well. The scan-line method was performed in six slopes by using a geological compass to determine rock mass structure on the rock slope, and the condition of joints such as persistence, aperture, roughness, infilling material, weathering and groundwater conditions. Slope kinematic analysis was performed employing a stereographic projection. The rock slope quality and stability were investigated based on RMR (rock mass rating) and SMR (slope mass rating) parameters. The rock slope kinematic analysis revealed that planar failure was likely to occur in Slope 1, 3, and 4, the wedge failure in Slope 1 and 6, and toppling failure in Slope 2, 5, and 6. The RMR rating is ranging from 57 to 64 and can be categorized as Fair to Good rock. The SMR rating revealed that the failure probability of Slope 3 was 90%, while it was from 40% to 60% for others. Despite the uniform RMR for all slopes, the SMR was significantly different. The detailed quantitative consideration of orientation of joint sets and geometry of the slope contributed to such differences in outcomes.