微承压水地层超深地下连续墙成槽稳定性分析

Groove Stability of Diaphragm Wall Excavation in Micro-confined Water Stratum

以苏州火车站综合改造工程中连续墙成槽施工为背景,结合一典型事故案例,通过现场施工、检测及计算分析,从地层条件、施工参数等方面探讨了微承压水地层中超深基坑地下连续墙的成槽稳定性问题。研究表明:微承压水地层是连续墙成槽塌孔的重要因素。抓斗施工时频繁抓土与上提,使其下方一定范围的泥浆受到负压影响而减弱护壁作用。地面超载较小时,槽壁最大变形与荷载增量成小幅线性增长,但较大超载可使土体剪切破坏、槽壁坍塌。提高泥浆体积质量,槽壁变形可显著减小。槽壁两侧采用旋喷桩加固,能有效提高薄弱土层的力学性能,阻隔承压含水层的作用,保护成槽稳定。

Based on the construction background of diaphragm wall groove of the renovation project at Suzhou Railway Station,and combined with a typical case of accident, also through construction practice, detection and simulation, the groove stability of diaphragm wall in micro-confined water stratum is studied from aspects of construction parameters and geological conditions. This study shows that,the micro-confined water stratum is an important factor in the collapse of slurry trench; the negative pressure in mud induced by the frequent excavation and pick-up of grab will weaken the slurry effect; when the overload on ground is small, the largest deformation of slurry wall will increase linearly with load increment, but the greater overload could induce shear failure in soils; the deformation of slurry trench reduces significantly with the increase of mud density. The reinforcement on both sides of slurry trench by jet grouting piles can effectively improve the mechanical properties of the weak soil layer and protect the stability in groove.