Design Optimization of a 4-Meter Cantilever Retaining Wall for Slope Stabilization in North Sumatra

Abstract

The slope failure occurring at the loading ramp area of the palm oil mill operated by Perkebunan Nusantara Nusantara resulted in significant operational disruptions, including delays in material handling and interruptions in processing activities. The failure was primarily attributed to the construction of the loading ramp over an unstable subsurface layer, which made the ground highly susceptible to deformation and slope instability. Consequently, a geotechnical investigation was required to determine an appropriate reinforcement strategy capable of restoring stability and ensuring the safe continuation of mill operations. This study evaluates the slope conditions before and after the installation of a cantilever retaining wall by employing numerical modeling based on the Finite Element Method (FEM). Two analytical scenarios were examined: the original unreinforced slope condition and the reinforced condition utilizing a 4-meter cantilever retaining wall. The results demonstrate that the unreinforced slope exhibited a safety factor below the minimum geotechnical design threshold, confirming its unstable condition. Following reinforcement, the safety factor increased to 1.506, thereby fulfilling standard stability requirements. These findings indicate that the installation of a cantilever retaining wall substantially enhances slope stability and effectively reduces the risk of future slope failures at the loading ramp area. The study underlines the critical role of appropriate retaining structures in maintaining the safety and continuity of industrial operations situated on geotechnically sensitive terrain.