Rock Slope Stability Evaluation on the Construction of New Road Shortcut 4 Border City of Singaraja - Mangwitani, Bali

Abstract

Shortcut 4 new national road development project on Singaraja - Mangwitani section Bali found a potential rock slide slope problem. An outcrop of igneous rock with an intensive joint was not expected to be encountered previously. The excavation work in road construction had to pay attention to the stability of the resulting rock slope considering that apart from the potential for slope failure, rock slope could also threaten the bridge abutment building in front of it. The location of the rock slope was on the edge of Lake Bratan which is geologically part of the early Holocene volcanic rocks, namely mountain rocks composed of tuff, lava and volcanic breccia. Anisotropic andesite slope was controlled by a discontinuous plane with a certain pattern. Rock Quality Assessment was carried out by the Rock Mass Rating (RMR) method and Slope Mass Rating (SMR) for slope stability evaluation. The planar, tople and wedge potensial slope failure were evaluated. The potential for planar slope failure has a value of SMR 30.18 (Unstable), 57.6 (Partialy Stable) for wedge slope failure potential and 47.6 (Partialy Stable) for tople slope failure potential. The SMR value indicated that the rock slope requires engineering threatment to become stable.