Excess pore water pressure effects on excavation stability of diaphragm walls in newly reclaimed offshore foundations

Marine soft clay, a typical problematic soil in marine and coastal engineering, poses significant threats to construction and long-term safety due to its characteristics of low permeability, low strength, and high compressibility. Focusing on the construction features of trench excavation for diaphragm walls for cross-sea bridge anchorage systems, this study specifically addresses the critical role of excess pore water pressure induced during the settlement of newly constructed foundations. This pressure dissipates slowly in low-permeability soft clay, directly impacting stability by reducing the soil's effective stress. Accordingly, this paper develops a computational model for the local stability of trench walls using the stress cell method and establishes an analysis method for overall stability based on the upper-bound theorem of limit analysis. Both approaches fully incorporate the hydro-mechanical effects of excess pore water pressure. The research ultimately derives a computational expression for the safety factor of trench wall stability considering the influence of this pressure and proposes corresponding control standards. To validate the effectiveness of the method, the calculated trench wall safety factors were compared with numerical simulation results; the comparative analysis shows that the safety factors obtained by this method are in close agreement with the numerical simulation results. Developed computational methods assessing both local and global stability of diaphragm wall excavations under excess pore water pressure.