Numerical Evaluation of Factor of Safety (FOS) and Anchor Pile Arrangement for Slope Stability Using GeoStudio (SLOPE/W)

Abstract

Slope stability is an important issue that should be prioritized in construction engineering because unstable slopes can cause landslides, property damage and risks to human life. In Malaysia, slope failures often happen due to steep slope cuts and weak soil. This study investigates slope performance under different soil conditions, including poorly graded soils, medium‑dense sand, dense silty sand, well‑graded sands, and well‑compacted soils or rock, combined with varying slope angles of 30°, 60°, and 90°. This study used GeoStudio software (SLOPE/W) with the Morgenstern-Price method to find the Factor of Safety (FOS) and to propose and optimize anchor pile system arrangement that can improve slope stability for the condition examined with external load. The slope height is six meters, and three slope angles were studied, 30°, 60° and 90°. Soil properties such as cohesion (0 to 20 kPa) and friction angle (5° to 45°) were varied to evaluation their effects on slope stability. The results showed that poorly graded soils had very low FOS values, 0.130 indicating unstable conditions, while well-compacted soils and rocks gave higher FOS values, 2.897. Anchors pile system was installed at a downward angle of 10° and a spacing of 3 meters for all condition of soils. The anchors increased the FOS by acting on friction and providing pull-out resistance. For slopes of 30° and 60°, the effect of anchors shows increased stability and increased the FOS past the safe limit of 1.30, as required by the JKR Guidelines. However, for very steep slopes, found that anchors alone were not sufficient, the recommendation indicated that other methods, retaining structures were required. Overall, this study demonstrated that anchor pile reinforcement significantly improves slope stability for moderate slopes but is insufficient for vertical slopes where additional retaining systems are required.