Zero extension line method for three-dimensional stability analysis in soil engineering

This paper presents a new approach for three-dimensional stability analysis of soils using the Zero Extension Line Method. The method assumes the intermediate principal stress-planes to be straight. The geometric considerations for obtaining the orientation of these planes in the plastic zone are described. The equilibrium-yield equations are integrated in these planes to give the total applicable load at the limiting equilibrium state. The method accounts for the nonasssociativity of soil behavior as well. It also considers the effect of partial mobilization of soil strength on the counter side of the slope, on its stability. Based on this method, a computer code, Slope3D8, has been written for three-dimensional stability analysis. Examples have been provided to show the capability of the model in analyzing three-dimensional stability of slopes under drained and undrained conditions. In-plan-curvature of slopes and the centrifugal force resulting from movement of vehicles in curved routes can also be modeled. The model predicts lower ultimate load as compared to the existing three dimensional limit analysis methods. Some of the difference in the results of these two models is due to the aggravating effect of counter side that is not considered by the developed three-dimensional limit analysis models. It has been concluded that the presented model provides a useful tool for three-dimensional stability analysis in soil engineering.