Effects of Soil Properties and Slope Angle on Deformation and Stability of Cut Slopes

The impact of soil parameters and slope angle on the deformation and stability of cut slopes is critical for defining road project safety measurement. This study investigates the effect of soil properties and slope angle on the deformation and stability of cut slopes in general and the specific Arba Minch-Chencha upgrading road project. Forty-eight (48) analyses were carried out both in Slope/W and Plaxis 2D software for six cut slopes and analyzed for four different slope angles. Twenty-four (24) dataset samples were collected from six different cut-slope sites. These dataset samples were categorized in two situations, i.e., before and after water saturation for each cut slope. The limit equilibrium method (LEM) comparison clearly showed that the Spencer, Bishop, and Morgenstern-Price methods produced similar FOS. The Ordinary and Janbu approaches, on the other hand, underestimate the FOS. Most LEMs except Ordinary and Janbu methods that estimated higher FOS than finite element method (FEM) analysis. It is observed that the main reasons for the cut-slope instability were the provision of steep cut-slope angles, the existence of a high proportion of fine soil, and moisture content, which was observed in both Plaxis 2D (FEM) and Slope/W (LEM). It was concluded that the slope is more stable for the soil having few fine-grained fractions. Moreover, flattening the slope stabilizes the cut slopes based on the results obtained from both Plaxis 2D and Slope/W.

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