基坑外设置隔离桩对土体水平位移的隔断效果分析

目前对于隔离桩是否能有效减小基坑外地下结构的变形问题仍存在争议。为研究隔离桩对基坑开挖引起的土体水平位移的隔断效果,结合二阶段分析方法及地层补偿法,提出了求解基坑开挖后隔离桩外土体位移的三阶段分析方法,并对其合理性进行了验证。结果表明:基于该方法的计算,不同基坑开挖深度和不同围护墙变形模式下,隔离桩的存在可减小坑外地坪下一定深度范围内的土体水平位移,但可能增大深层土体水平位移;隔离桩刚度越大,对土体上部水平向位移的隔离效果越好,但同时深层土层位移增大的情况也越明显;合理的隔离桩桩顶埋深可一定程度减小隔离桩对深层土体的牵引作用。为保护基坑外的地下结构而设置隔离桩时,应根据模拟计算结果、工程实际情况及当地经验综合分析其可行性。

Effect Analysis of Isolation Piles outside Foundation Pit onControlling Lateral Soil Displacement

Currently, it is still controversial whether isolation piles can effectively reduce the deformation of underground structures outside foundation pits. In order to study the effect of isolation piles on lateral soil displacement induced by excavation, a three-stage method is presented to study the soil movement outside isolation piles after excavation by combining the two-stage method and the stratum compensation method, and the rationality of the proposed method is verified. The calculated results show that, under different excavation depths and deformation modes of the foundation pit, lateral soil displacement in a certain depth range under the ground surface can be reduced by the isolation piles, however the horizontal displacement of the deep soil is increased; with the increase of the stiffness of the isolation piles, the isolation effect on the lateral displacement of the top soil becomes more significant, but there are more deep lateral soil displacement; the drag effect to the deep soil due to the isolation piles can be reduced with a reasonable buried depth. When consider setting isolation piles to protect the underground structures outside the foundation pit, its feasibility should be comprehensively analyzed according to the simulate results, the practical engineering condition and the local experience.