为保障邻近运营高铁桥梁的结构安全,系统研究了不同围护结构形式对沉井下沉引发土体变形的控制效果。依托南通李港水厂工程,建立三维有限元模型,首先比选无围护、平面地连墙及环形地连墙三种方案的控制效能,并通过现场监测数据验证了模型的准确性。同时基于最优的环形地连墙方案,进一步分析其厚度与半径参数的影响规律。结果表明:(1)通过系统比选无地连墙、平面地连墙及环形地连墙三种方案,证实环形地连墙对沉井施工引发的土体变形控制效果最优,尤其能显著降低近桥墩区域的地表沉降和水平位移,满足高铁桥梁对临近施工变形的严苛要求;(2)与无围护结构相比,采用地连墙可显著降低沉井施工引起的地表沉降和水平位移,环形地连墙和平面地连墙条件下地表最大沉降值分别由150 mm降至2.5 mm和16 mm,沉井外10 m处径向位移值由32 mm降至0.5 mm和18 mm;(3)地连墙厚度对墙内夹层土体的变形影响较弱,但对墙外侧土体变形具有显著控制效果,墙厚增加时,墙外土体最大径向变形及地表沉降边界呈现先减小后增大的变化趋势,最优厚度为1.2 m;(4)在地连墙半径为13.5~17.5 m范围内,半径越大,地表最大沉降值越显著。

To ensure the structural safety of adjacent high-speed railway bridges during construction, this study systematically investigates the control effects of different retaining structures on soil deformation induced by caisson sinking. Taking the Nantong Ligang Water Plant Project, as a case study a three-dimensional finite element model was established to compare the effectiveness of three schemes: no retaining structure, planar diaphragm walls, and circular diaphragm walls. The accuracy of the model was verified using field monitoring data. Furthermore, based on the optimal circular diaphragm wall scheme, the influence of wall thickness and radius parameters was analyzed in detail. The results show that: (1) Through systematic comparison of the three schemes—no diaphragm wall, planar diaphragm wall, and circular diaphragm wall—the circular diaphragm wall was proven to be the most effective in controlling soil deformation induced by caisson construction. It significantly reduces surface settlement and horizontal displacement near bridge piers, meeting the stringent post-construction deformation requirements of high-speed railway bridges. (2) Compared with the case without a retaining structure, diaphragm walls significantly reduce ground settlement and horizontal displacement caused by caisson sinking. Under circular and planar diaphragm wall constraints, the maximum surface settlement decreased from 150 mm to 2.5 mm and 16 mm, respectively, while the radial displacement 10 m outside the caisson decreased from 32 mm to 0.5 mm and 18 mm, effectively enhancing the safety of bridge operations; (3) The diaphragm wall thickness has limited influence on the deformation of the inner sandwich soil but exhibits a significant control effect on the outer soil. As the wall thickness increases, the maximum radial deformation and the 1 mm surface settlement boundary of the outer soil show a trend of first decreasing and then increasing, with an optimal thickness of 1.2 m; (4) Within the range of diaphragm wall radii from 13.5 m to 17.5 m, larger radii significantly increase the maximum surface settlement, indicating the need for a balance between stiffness and structural stress.