LAUSR

A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft for its efficiency, safety and sustainability. Full-scale field tests and numerical analysis were conducted to analyze the base failure of the circular shaft with confined water. The failure process of the shaft was observed on site. The construction process of step-by-step excavation of shaft and layer-by-layer assembly of pre-stressed structure was simulated in detail. Simulation results agree well with the phenomenon on site. The base failure modes present that tensile damage generates at the center of the base due to non-uniform uplift and shear failure occurs along the soil-structure interface. The effects of shaft size and confined water head were also discussed. As a result, a critical ratio of diameter to shaft depth is put forward to assess the size effect of circular shaft. A conclusion that the soil strength should be partially considered in anti-inrushing safety factor calculation is drawn by analysis and comparison of various calculation methods. This research provides a reference for the base stability evaluation of similar shaft subjected to hydraulic uplift. 在中国广州市某高水压砂土地层拟进行顶管工作井施工. 拟采用一种安全、高效、环保的新型装配式支护结构用于圆形工作井支护. 本文通过现场原位试验和数值模拟, 分析了圆形竖井受承压水作用下的基底破坏机理. 现场试验获得了竖井基底在承压水作用下的破坏过程, 并通过数值软件精细化模拟了竖井分层开挖和装配式结构逐层支护的施工过程. 结果表明, 模拟结果与施工现场现象吻合较好, 基底破坏模式呈现出在基底中心的拉伸破坏和沿着土与支护结构接触面的剪切破坏. 文章还讨论了竖井尺寸和承压水水头对基底失稳的影响规律, 并提出了可用于评价圆形竖井尺寸效应的竖井直径与竖井深度的临界比值. 通过对五种抗突涌安全系数计算方法的分析, 得出在抗突涌安全系数计算时应部分考虑土体强度. 本研究可为类似受承压水作用的圆形竖井基底稳定性评价提供参考.