The Effect of Soil Heterogeneity and Weak Layers for the Safety Factor of Slope

This study was conducted to determine the effect of soil heterogeneity and the presence of a weak layer between strong dominant soils on slope stability. The limit equilibrium using Bishop simplified method was used to determine the safety factor on the slope with four variations of groundwater level elevation, consisting of twenty-two slope models with varying numbers of dimension, orientation, and position of the weak layer. In addition, soil parameters are also made different in each modeling, representing heterogeneity with the weak layer significantly affected by the slope's safety factor. This research focuses on the effect of soil heterogeneity and the presence of different weak layers and groundwater elevation, which varies with the safety factor to determine the stability of a slope. A thin cohesive layer within the cohesionless dominant layer increases the safety factor. Conversely, a cohesionless thin layer within the cohesive dominant layer reduces the slope safety factor. Moreover, the dimension, orientation, and position of the weak layer can also affect the stability of the slope. The result showed that the heterogeneity and presence of a thin layer between homogeneous soils need to be considered during stability analysis. Under certain conditions, the presence of a thin layer of different types on a dominant soil increases the safety factor instead of other conditions. Therefore, soil testing to obtain parameters needs to be carried out carefully and can cover the parameters of all soil layers.