The effect of slope height and angle on the safety factor and modes of failure of 3D slopes analysis using limit equilibrium method

Abstract

Abstract Background It is a well-known fact that the safety of slopes majorly depends on several factors such as geometry, soil properties. The safety factor might change significantly depending on the soil type and the slope’s shape. The knowledge of the nature of the change in the safety factor due to the change in the slope’s height and angle is essential for implementing an effective strategy of increasing the safety factor for any slope stability problem. The influence of geometric shapes on the stability of the slope needs to be properly investigated through three-dimensional slope stability analysis, as the three-dimensional analysis is suitable for all slopes, even those which invalidate the plane-strain conditions. Results To calculate the three-dimensional safety factor, multiple analyses of three homogenous soil slopes with different soil properties were conducted by varying slope height, angle, and combinations. Each slope's height and angle were recorded to identify the types of slope failure. The analysis’s findings showed that while a decrease in height raises the safety factor nonlinearly, a decrease in slope angle increases the safety factor almost linearly. Base failure is the most likely failure for slopes with a height less than 4.0 m and an angle of inclination less than 18°. On clay and sandy clay soils, toe slide is the most common type of slope failure. The expected failure type will be either toe or face failure when the slope's height and base angle exceeds 5.0 m and 22°, respectively. This study also found that the three-dimensional safety factor for soil slope is generally 10–20% higher than the two-dimensional factor of slope safety. Conclusions The slope’s nature depended on the soil type and slope form, but the safety factor increased as the slope angle and height decreased. To determine the most efficient method for slope stabilization, it is necessary to do an extensive study on slope height and angle reduction techniques. It should be ensured that the sliding mass of soil does not rise, resulting in a potential slope failure. The present study will help identify the correlation between the height and base inclination of the slope with the expected nature of slope failure. The present study helps to investigate the variation of the safety factor of a three-dimensional homogenous soil slope subjected to self-weight only. The study can be further extended to observe the variation of the factor of safety for a 3D slope subjected to pore water pressure and seismic loading also.