主动控制预制压入式沉井侧壁和刃脚邻近土体应力路径演化与变形响应特征OACHSSCD

Under the construction of an active control press-in prefabricated shaft(ACPP),the evolution of stress paths and the mechanisms governing the deformation response of the surrounding soils remain insufficiently understood.To clarify the underlying behavior and support stability assessment and safety control during shaft sinking,this study is based on the ACPP emergency shaft of Beiqing Road Station on Shanghai Metro Line 13 and adopts an integrated approach combining numerical simulation and laboratory stress-path testing.The entire sinking process was simulated using ABAQUS,from which representative stress paths of soil elements at different depths adjacent to the sidewall and the cutting edge were extracted and then mapped as loading histories for stress-path triaxial tests to investigate soil mechanical responses under different stress paths.Results indicate that,under ACPP conditions,the stress paths of soils along the shaft side exhibit pronounced stratification:the shallow zone is dominated by stress release induced by excavation unloading;the middle zone develops a typical unloading-reloading cyclic path with the most significant stress redistribution;and the deep zone near the cutting edge shows stepwise reloading recovery of confining pressure after progressive unloading,while axial stress either accumulates continuously or undergoes minor adjustments.The tests further show that the middle soft clay experiences more pronounced radial rebound during unloading,suggesting a potentially sensitive interval for fluctuations in sinking rate and differential settlement.These findings provide a reference for mechanical analysis,construction pacing optimization,and safety control of ACPP shaft sinking.