Effect of earthquake loading on tension cracks and factor of safety in slope stability analyses

Seismic loading and ground water pressures are two major factors contributing to slope instability. Earthquake shaking can increase shear stresses in soils and thereby reduce the factor of safety. In addition, earthquake loading can influence the shape of failure surface, particularly when tension cracks are present. In cohesive materials, a tension crack often occurs at the crest of slopes and the depth of this crack can be influenced by earthquake loading as depth of tension crack can be related to the factor of safety. In this study, the effect was studied for non-circular failure surfaces using a simple genetic algorithm and the Morgenstern-Price method. Analysis shows that as the peak horizontal acceleration due to earthquake loading increases, the depth of tension crack increases and the factor of safety decreases. The effect of seismic loading on the shape of non-circular failure surfaces is also illustrated.