Safety Factors Investigation Based on FEM and LEM Approach in Toll Road Embankment Slope

Abstract

The Pejagan-Pemalang toll road which is a Section II project was designed at different embankment heights on soft soil subgrade. The process involved investigating the slope stability of these embankments through the determination of the safety factor. This can be achieved using different methods such as the limit equilibrium method (LEM) and the finite element method (FEM) which are considered the standard approaches. However, the presentation of different numerous results for the safety factors (SF) in landslide calculations usually makes it difficult for the engineer to understand some uncertain conditions. Therefore, this study aims to determine the safety factors using LEM and FEM approaches at different conditions. The soil subgrade used was in SPT and three models of the properties were obtained. Moreover, a Geo-Studio program with Slope-W analysis was applied using the Morgenstern-Price for the LEM and PLAXIS for the FEM. The height was varied at 2 to 8m with the slope H: V at 1:1, 1:1.5, and 1:2. The simulation was conducted at three different levels of groundwater. The results showed that the height, embankment geometry, and groundwater levels were affected in the SF analysis using the two methods. It was also discovered in all categories that higher embankments had smaller SF while the higher angle of slope produced a higher SF. Furthermore, the properties of the soft soil were observed to have influenced the SF result as indicated by the narrow difference in the correlation between the embankment height and SF. The results of the LEM and FEM were also compared and the observations were explained. The findings of this study are expected to serve as a guide for engineers, especially those in road toll projects, to determine the optimum model needed to predict slope failure in embankments for toll roads.