长大深基坑施工围岩动态变形规律

Dynamic deformation analysis of surrounding rock in large-long-deep foundation pit construction

针对目前对深基坑施工围岩动态变形规律缺乏系统研究的现状,以武广客运专线上的金沙洲隧道明挖段深基坑工程为实例,建立空间有限元模型,实现了施工动态模拟;分析了长大深基坑施工过程中,各部位围岩的动态变形和分布规律,并指出了围岩变形的关键位置与施工环节。研究结果表明:坑周土体沉降在竖直方向表现为沿深度逐步减小,最大值出现在地表,但在水平方向上,沉降规律较复杂,受到围护桩自身刚度的影响,呈现为"勺"形,最大沉降位置并非出现在桩顶位置,而是离桩顶约11 m处;坑周土体水平位移随基坑开挖逐渐增大,且位移中心逐渐下移,直至开挖深度2/3处;基坑开挖后,基底产生一定程度的回弹和内挤变形,开挖深度越大,土体条件越差,变形越大。

According to the present situation that there is lack of a system research about the dynamic change law of surrounding rock in deep foundation pit construction, Jinshazhou tunnel open cut works on Wuguang passenger dedicated line was taken as an engineering example, a spatial FEM model was established, which implemented the construction dynamic simulation, and an overall analysis about the dynamic deformation law and distribution of surrounding rock was made. The results show that the settlement of soil around deep foundation pit decreases gradually along the depth and the maximum value appears in ground surface, but on horizontal direction, the subsidence rule is more complex influenced by the retaining pile own rigidity, the settlement curve represented as ＂spoon - like＂ and the biggest subsidence position appears by no means in the head of piles, but leaves the head of pile approximately 11 m. The horizontal displacement of soil around deep foundation pit increases gradually with excavation, and the displacement center moves gradually until cutting depth 2/3. The basement will gener- ate uplift and in -push in some degree after the inner soil is excavated, and the cutting depth is bigger, the soil condition is worse, and the deformation is bigger.