[关键词]
[摘要]
基坑降水是引起土体变形的一个重要因素,而针对降水条件下平行于基坑的邻近盾构隧道变形却少有研究。为探讨基坑降水引起的既有隧道受力变形特性,依托实际工程建立三维数值模型,以隧道的最大竖向位移为评价指标,使用正交表筛选最优组合和主要影响因素,而后对主要影响因素进行单变量分析,研究隧道受力变形规律。研究表明:通过极差分析和方差分析发现,连续墙插入深度s是影响坑外隧道最大竖向位移的主要因素,故邻近既有隧道的新建基坑工程有降水需求时,可先选取该因素进行隧道变形控制。随着连续墙插入深度的增加,隧道的弯矩和变形均会随之减少,当连续墙插入深度到达透水性较差的土层后隧道变形显著减小,此时隧道变形能得到有效控制,而继续增加插入深度对于控制隧道变形意义不大。降水使坑外邻近隧道产生朝向坑内斜向下的“横鸭蛋”沉降变形,施工过程中应重点关注隧道拱顶和邻近基坑侧拱腰的变形情况。
[Key word]
[Abstract]
Foundation pit dewatering is an important factor causing soil deformation. However, there are few studies on the deformation of adjacent shield tunnels parallel to the foundation pit under dewatering conditions. In order to explore the stress and deformation characteristics of the existing tunnel caused by foundation pit dewatering, a three-dimensional numerical model is established based on the actual project. Taking the maximum vertical displacement of the tunnel as the evaluation index, the orthogonal table is used to screen the optimal combination and the main influencing factors, and then the main influencing factors are analyzed by univariate analysis to study the stress and deformation law of the tunnel. The research shows that through range analysis and variance analysis, it is found that the insertion depth s of the diaphragm wall is the main factor affecting the maximum vertical displacement of the tunnel outside the pit. Therefore, when the new foundation pit project adjacent to the existing tunnel has dewatering demand, this factor can be selected first to control the tunnel deformation. With the increase of the insertion depth of the diaphragm wall, the bending moment and deformation of the tunnel will decrease. After the insertion depth of the diaphragm wall reaches the soil layer with poor water permeability, the deformation of the tunnel will decrease significantly. At this time, the deformation of the tunnel can be effectively controlled, and it is of little significance to control the deformation of the tunnel by increasing the insertion depth. The dewatering causes the adjacent tunnel outside the pit to produce the "horizontal duck egg" settlement deformation towards the pit obliquely downward, and the deformation of the tunnel vault and the side arch waist of the adjacent foundation pit should be focused on during the construction process.
[中图分类号]
TU921
[基金项目]
国家自然科学(52238009);江西省自然科学基金(20224BAB214068,20223BBG71018);江西省研究生创新资金(YC2021-S433).