基坑开挖下的地表沉降简化分析法

A SIMPLIFIED ANALYSIS METHOD FOR EVALUATING THE HORIZONTAL DEFORMATION OF SINGLE PILE UNDER ADJACENT FOUNDATION PIT EXCAVATION

如何准确预测基坑开挖引起的坑外地表土体沉降具有重要意义。利用虚拟镜像技术,推导了由圆孔收缩产生的地层位移解析式,分析中首次定义了土体的不均匀收缩系数,能够考虑土体的不均匀收缩。在此基础上结合面积等效原理,给出了基坑开挖下的坑外地表土体沉降解析式。与收集的2个实际工程案例对比,验证了该解析式的正确性,进一步参数分析表明,坑外地表沉降大小会随距离基坑的由远及近近似呈非线性增大;且均匀收缩下的地表沉降计算值较实测出现一定的偏小,随不均匀收缩系数的增大,坑外地表沉降计算值越大,但会逐渐收敛;而当不均匀收缩系数在3～6之间时,计算值与实测吻合较好。研究成果可为类似工程提供一定理论指导。

It is of great significance to predict the surface settlement caused by excavation of foundation pit. Firstly, by using the virtual image mirror technique, the analytic ground settlement generated by circular holes contraction is derived. Moreover, the inhomogeneous shrinkage coefficient of soil is obtained, and the analytical formula for the settlement of the surface soil outside the pit is given with the combination of the area equivalent principle. Secondly, the measured results from two well documented published cases are selected to compare with the results calculated with this proposed method to verify the correctness of the analytical formula. Finally, further parameter analysis shows: there is a nonlinear relationship between the ground settlement and the distance from the foundation pit. The calculated value of ground settlement under uniform shrinkage is smaller than that measured. Besides, the calculated value of surface subsidence outside the pit increases with the increase of non-uniform contraction coefficient, but it will converge gradually. When the non-uniform shrinkage coefficient is between 3~6, the calculated value meets well with the measured data. The research results can provide certain theoretical guidance for similar projects.