Limit Analysis for 3D Stability of Slurry Trench under Unsaturated Seepage Conditions

To address the engineering problem of wall collapse and destabilization during the construction of underground diaphragm wall trenching, an upper bound limit analysis method, combined with the three-dimensional rotation failure mechanism, was applied to investigate the stability of the underground diaphragm wall slurry trench under the condition of three-dimensional unsaturated stable seepage. The expression of the safety factor of the unsaturated soil slurry trench was deduced by the energy balance Equation (Eq.). Additionally, a genetic algorithm was used to search for the minimum safety factor and the critical slip surface, and the effects of relevant parameters on the stability of slurry trench under the condition of unsaturated seepage were analyzed in detail. The safety factor rises as the ratio of slurry to soil bulk density increases, along with cohesion and friction angle. The existence of suction in unsaturated soil is beneficial to the stability of slurry trench, and the suction-induced effect is highly dependent on seepage conditions and soil types. Different seepage conditions have the most significant effect on stability of clayey slurry trench; however, the effect obviously weaken in silt, and almost completely disappear in losses and sand. The decrease in the slurry level height will lead to the increase in the area of critical slip surface, and the influence of different seepage conditions on the critical slip surface of clayey slurry trench is significant, while the influence on sandy slurry trench can be negligible. The findings of this research can offer valuable theoretical insights for the design of underground diaphragm wall trenches in unsaturated seepage conditions.