考虑施工影响的地下连续墙环向等效支撑刚度分析

Analysis on Circumferential Equivalent Strut Stiffness of Diaphragm Wall Considering Construction Impact

摘要:

由于环拱效应能够充分发挥混凝土抗压强度高的特点，圆形地下连续墙围护结构在超深竖井基坑中应用广泛。环向等效支撑刚度取值是圆形地下连续墙围护结构设计中的重要参数。由于地下连续墙在实际施工过程中采用折线拟合圆形，且存在地表荷载分布不均匀或土层分布不均匀等情况，这些因素会对环向等效支撑刚度产生影响。使用有限差分单元法建立计算模型，分析了基坑实际形状、不均匀荷载分布对环向等效支撑刚度的影响。计算结果表明，圆形地下连续墙的环向等效支撑刚度，在折线长度为2 m时与圆形理论解基本一致，当折线长度为3 m时，需要根据竖井直径进行折减。同时，不均匀荷载对环向等效支撑刚度造成的折减效果显著，荷载分布不均匀程度越大，竖井直径越大，环向等效支撑刚度折减越大。

Abstract:

The enclosure structure of circular diaphragm wall is widely used in ultra-deep shaft foundation pit because of the ring arch effect able to fully play the characteristics of high compressive strength of concrete. The value of circumferential equivalent strut stiffness is a very important parameter in the design of circular diaphragm wall enclosure structure. In practice， because the diaphragm wall adopts the polyline to fit the circle， and the surface load distribution is uneven or the soil layer distribution is uneven， these factors will affect the circumferential equivalent strut stiffness. The finite difference element method is used to establish a calculation model to analyze the effect of the actual shape of foundation pit and the uneven load distribution on the circumferential equivalent strut stiffness. The results show that the circumferential equivalent strut stiffness of the circular diaphragm wall is basically consistent with the circular theoretical solution when the polyline length is 2 m. When the polyline length is 3 m， it is necessary to reduce the polyline according to the diameter of the shaft. At the same time， the non-uniform load has a significant effect of polyline reduction caused by the circumferential equivalent strut stiffness. The greater the non-uniform load distribution is and the larger the shaft diameter is， the greater the polyline reduction of the circumferential equivalent strut stiffness is.