深基坑内支撑拆除时地下连续墙水平位移计算方法

Calculation Method of Horizontal Displacement of Diaphragm Wall in Deep Foundation Pit during Internal Support Removal

深基坑地下连续墙最大水平位移一般出现在内支撑拆除阶段。基于弹性变形的叠加原理,考虑拆撑过程中地下连续墙产生的水平位移增量为由自由变形量和补偿变形量的叠加,将地下结构底板与地下连续墙的接触处考虑为固定端,然后利用极限平衡法获得了墙体水平位移变化规律。最后以北京地铁12号线三元桥车站“地下连续墙+钢支撑”深基坑工程和北京朝阳区霞光里“地下连续墙+钢筋混凝土内支撑”深基坑工程为背景,计算分析了不同拆撑阶段地下连续墙的水平位移增量。结果表明:通过所建立的计算方法获得的拆撑后地下连续墙水平位移曲线与实测曲线较为符合;拆撑后地下连续墙上部水平位移增量比下部大,为下部的2~5倍;拆撑过程中地下连续墙水平位移最大值位置发生上移,上移量约0.15H~0.2H;计算结果可为类似工程提供重要理论参考。

The maximum horizontal displacement of underground diaphragm wall of deep foundation pit usually occurs in the internal support removal stage.Based on the superposition principle of elastic deformation,the horizontal displacement increment of the diaphragm wall is considered as the superposition of free deformation and compensation deformation.The contact point between the bottom plate and the diaphragm wall is considered as the fixed end.Then the variation rule of the horizontal displacement of the diaphragm wall is obtained by the limit equilibrium method.Finally,the horizontal displacement increments of the underground diaphragm wall at different stages of dismantling the bracing are calculated and analyzed against the background of two examples of deep foundation pit projects——the deep foundation pit engineering of "underground continuous wall + steel bracing" in Sanyuan Bridge station of Beijing Metro Line 12 and "underground continuous wall + reinforced concrete internal bracing" in Xiaguangli,Chaoyang District,Beijing.The results show that:The horizontal displacement curve of the diaphragm wall obtained by the established method is in good agreement with the measured curve.The horizontal displacement increment of the diaphragm wall is 2~5 times larger than that of the bottom.The maximum horizontal displacement of the diaphragm wall moves up in the process of bracing removal,with an upward displacement of about 0.15H ~ 0.2H.The results can provide important theoretical reference for similar projects.