the effects of longitudinal dimension in three dimensional slope stability analysis

Of late, three dimensional slope stability analysis has gained popularity among the geotechnical engineers so that the actual response of slope failure, which essentially occurs in 3d, can be captured. however, three dimensional slope failure analysis necessitates the proper consideration of the third/longitudinal dimension of the slope. three dimensional slope stability analysis can yield erroneous results if inadequate length of the third dimension of the slope is used during analysis. this study employs bishop’s simplified approach to find the minimum length of a 3d soil slope’s third/longitudinal direction to be considered during analysis. a parametric study compares the findings of 3d and 2d analyses for different geometries, pore pressure ratios and seismic loading for a cohesive-frictional slope. a total of 15 loading cases have been analyzed to study the convergence behavior of the 3d and 2d factor of safety (fs) values for slopes with different inclination angles and longitudinal length-to-height (l/h) ratios. the results presented in this study dictate that the longitudinal/third dimension of a 3d slope model should be at least five times the slope’s height for accurate 3d slope analysis. for all loading situations, whether a slope will collapse at the base or toe and the failure mass volumes are estimated. as the base inclination angle increases for a particular slope, the type of failure gradually shifts from base failure to toe failure. the volume of failure mass is seen to follow a decreasing trend with an increase in the slope angle.