Modeling rock slope stability using kinematic, limit equilibrium and finite-element methods along Mertule Maryam-Mekane Selam road, central Ethiopia

Slope failures are among the most common natural geohazards in the world's hilly and mountainous terrains causing loss of life and damage to infrastructures. The road connecting Mertule Maryam and Mekane Selam towns in central Ethiopia passes through extremely rugged terrain with steep hills and deep valleys/gorges. The purpose of this study is to identify and model the stability of selected rock slope sections along the road. For this, a detailed field investigation, including discontinuity survey, in situ rock testing, rock sampling, measuring slope geometry, and orientation, were carried out. From field observations, eight critical rock slope sections were identified for stability modeling using kinematic, limit equilibrium and finite-element methods. Kinematic modeling, which was performed with dips software, showed wedge and toppling modes of failures at slope sections RSS1 and RSS4, respectively, while planar mode of failure for RSS5 and RSS7. Moreover, limit equilibrium method (LEM) and finite-element method (FEM) models were used to determine the factor of safety (FoS) and the stress reduction factor (SRF), respectively, using Swedge, Rocplane, and Roctopple softwares for wedge, planar, and toppling failures, respectively. These modeling approaches were conducted for static dry, static saturated, dynamic dry, and dynamic saturated conditions. The modeling results at these critical rock slope sections showed that these slopes are stable if FoS/SRF > 1 and unstable if FoS/SRF < 1. The performance of remedial measures at different slope profiles based on LEM modeling showed that reducing the slope angle, slope height, and benching a slope have improved the overall stability of rock slopes. Moreover, this study also recommends the application of shotcrete, rock bolts, anchors, and retaining walls to prevent the failure of the critical rock slope sections along the road.