基于影像源法的基坑开挖引起的土体水平位移预测

基坑开挖将使土体产生附加水平位移,过大的水平位移会使邻近地下结构物受到破坏。基于影像源法,并充分发挥基坑围护结构易于实测的优势,推导了在基坑开挖下的坑外土体水平位移半解析式,分析中,通过定义土体的不均匀收敛系数,考虑了当前研究中大都忽略的土体收敛非均匀性,与实际情况更接近。同工程实测数据的对比验证了所提方法的准确性。进一步参数分析表明:不考虑土体收敛非均匀性的坑外土体水平位移计算值同实测相比,会低估上部土体水平位移,高估下部土体水平位移,因而同实测出现一定偏差,且当土体愈靠近基坑,偏差愈明显,可见考虑土体的非均匀收敛愈有必要。计算发现,当不均匀系数介于3～6时,计算结果同实测吻合较好。本文研究成果可为预测基坑开挖诱发土体水平位移提供一种新的探究思路。

Prediction of horizontal displacement of soils caused by excavation of foundation pits based on virtual mirror technology

The excavation of foundation pits will cause additional horizontal displacement of soils, and the excessive horizontal displacement will damage the adjacent underground structures. Thus, based on the virtual mirror technology and taking full advantages of the easy measurement of deformation of retaining structures, the semi-analytical formula for horizontal displacement of soils outside pits under excavation is derived, during which the uneven shrinkage coefficient of soils is defined, so the non-uniform convergence of soils, neglected in the current researches, is considered. Then, the measured results from the published case are selected to be compared with the proposed analytical solutions. Fairly good agreements are obtained between the proposed method and the measurements. And further parameter analysis shows for the horizontal displacement of soils outside the foundation pits, the calculated results without considering the uneven shrinkage of the soils will underestimate that of the upper soil and overestimate that of the lower soil, Therefore, there is a certain deviation from the measured values. And when the soils are nearer to the foundation pits, the deviation is more obvious, so to consider the uneven shrinkage of the soils is necessary. When the non-uniform coefficient is between 3 and 6, the calculated value is in good agreement with the measured one. The proposed method can provide a new way to predict the horizontal displacement of soils induced by excavation of foundation pits.