Counterweight Reinforcement versus Slope Geometry Redesign for the Block 16 Sidewall at PT XYZ

Abstract

Landslides occurred on the Block 16 sidewall at PT XYZ, where the upper benches comprise low-stability fill and the lower benches comprise bedded rock. This study characterized the rock mass, assessed discontinuity-controlled failure potential, calibrated the failed-slope condition by back analysis, and compared counterweight reinforcement with slope-geometry redesign. Scanline mapping, Rock Mass Rating (RMR), stereographic kinematic analysis, Slope Mass Rating (SMR), and Bishop-simplified limit-equilibrium simulations in Slide 6.0 were applied. The lower rock benches had an average RMR of 69.5 and an SMR of 68.6. Oblique-toppling criteria were satisfied by 7.62% of the analyzed discontinuities. The initial model yielded an SF of 1.239, while back analysis reproduced the failure condition at SF = 0.995. Counterweighting increased SF to 1.324 using 42.6 m³/m of fill; geometry redesign produced SF = 1.352 with 264.98 m³/m of excavation. Both alternatives met the SF > 1.3 criterion, but counterweighting required substantially less material handling.