Simplified Mechanism for Evaluating the Basal Stability of Narrow-Deep Excavation in Nonhomogeneous Clay

The limit analysis method is extensively used in basal heave stability analysis of deep excavations. However, the quality of the safety factor determination by this method is significantly affected by the chosen failure mechanism. The classical Prandtl failure mechanism did not adequately take excavation aspect ratio and wall embedment depth into account. Moreover, it could not be effectively applied to nonhomogeneous clay where the undrained shear strength of soil varies linearly with depth. Based on that, a three-parameter variable failure mechanism is introduced. Subsequently, based on a series of optimization analyses and simplification, a simplified analytical mechanism is proposed and then verified. The obtained results show that compared with the Prandtl failure mechanism, the simplified mechanism can improve the prediction of the safety factor of basal heave stability for narrow-deep excavation in nonhomogeneous clay.