北京地铁车站地连墙支护结构受力变形特性研究

Mechanical and deformation characteristics of diaphragm wall system of Beijing metro station

北京地铁14号线望京站采用地下连续墙+钢支撑以及地下连续墙+钢支撑+锚索混合支护体系。基于监测数据分析研究表明:基坑开挖对周围土体的影响水平范围上与基坑深度相当。钢支撑区段与混合支撑区段的沉降槽形态有差异,混合支撑区段地表沉降要大于钢支撑区段的地表沉降。在混合支撑区段,当基坑开挖较浅时,地下连续墙呈悬臂式位移分布,随着基坑开挖深度的增加,呈现抛物线型位移;第一层部分钢支撑轴力接近工作轴力,而下层锚索的拉力未能得到充分发挥。在钢支撑区段,地下连续墙体变形呈现刚性移动特点,钢支撑在预加轴力后经历了应力松弛然后轴力不断增长的过程,具有明显的时空效应。盾构井段角撑轴力变化比较平缓,波动幅度不大,结构空间效应明显。两种支撑体系均能满足围护结构变形控制指标要求。

Wangjing station of Beijing metro line No. 14 adopts the support system of underground diaphragm wall + steel support as well as diaphragm wall + steel support + anchor cable. The analysis of monitoring data shows that the influence range of excavation on the surrounding soil is close to the depth of foundation pit. The shapes of settling tank s of steel support section and mixed support section are different. The surface subsidence of mixed support section is larger than that of steel support section. In the mixed support section, when the excavation of foundation pit is shallow, the displacement of diaphragm wall is cantilever distributed. With the increase of excavation depth, the displacement is parabolic. The axial forces of first layer of steel strut are close to the work ones, and the tension of the lower anchor cable does not give full play. In the steel support section, the deformation of diaphragm wall presents rigid motion characteristics. The axial forces of steel support presenting stress relaxation and growing process have obvious effects of time and space. The axial forces of angle brace of steel support at shield well are quite gentle, the fluctuation is not large, and the spatial effects of structure are obvious. Two kinds of supporting system both can satisfy the requirements of deformation control indices of retaining structures.