Abstract

Slope stability analyses are performed mostly as a two-dimensional (2D) section under the assumption of plane strain conditions, without much consideration to the impact of three-dimensional (3D) shapes. For natural slopes that have the complexities of slope surfaces, 3D modeling may also be considered since it can represent the more realistic geometry of the slope. However, previous studies show that the factor of safety (FS) as a result of 3D analyses mostly overestimated the FS from 2D analyses. This may lead to a long discussion on whether the 3D analysis is still applicable for the natural slopes, and could it represent the same results as the 2D analysis. This study was conducted using the finite element method for calculating the 2D and 3D FS of Pasir Muncang natural slope in order to observe differences of FS resulted from both analyses. A comparison of the FS from the 2D and 3D analyses, and also verification of sensitivity on several factors that impact the 2D and 3D models have been performed. The results of this study has indicated that some factors such as soil parameters, contour interval, and mesh coarseness greatly affect the results of the 2D and 3D calculations. Having carefully selected the aforementioned factors as the inputs for calculations, the difference between the FS values of 3D and 2D analyses becomes smaller. The final result of FS for this case study from the 3D analysis was still higher than the one from the 2D analysis, with the ratio of FS from 3D to FS from 2D was 1.44. It can be inferred that the use of 3D analyses needs more accurate data selections compared to the 2D analyses.

Highlights

  • The purpose of slope stability analysis is to estimate the safety of a slope by calculating factor of safety (FS) of the slope

  • This study has been conducted to compare the results of natural slope stability modeling in 2D and 3D by taking a case study of Pasir Muncang natural slopes, West Java, Indonesia

  • The results showed that the 3D calculation is slightly higher than most of the 2D calculations

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Summary

Introduction

The purpose of slope stability analysis is to estimate the safety of a slope by calculating factor of safety (FS) of the slope. Various methods exist for slope stability analysis, one of them is the finite element method (FEM). 2D modeling often cannot represent the actual geometry conditions of the slopes, especially for natural slopes that have a complex geometry. Another advantage of 3D analysis is that the finite element procedure can show the least stable slope surface. This is not a case in the 2D analysis where the most critical section should be assumed in advance. The stability analyses and slope modeling in this study used the finite element softwares PLAXIS 2D and PLAXIS 3D

Study Area
Literature Review
Methodology
Determination of 2D Critical Cross Section
Initial Result of 2D and 3D Stability Analyses on the Case Study
Section IV
Validation of Behaviour of 2D and 3D Slope Stability Analyses
Effects of the Selection of Soil Parameters
Effects of Contour Interval
Effects of the Size of Mesh
Conclusion
Full Text
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