郑州地铁3号线某车站8号出入口采用大断面矩形顶管施工,近距离垂直下穿DN2000污水管线,采用MJS工法对污水管线底部土体进行加固,对顶管过程的地表和管线位移进行实时监测,通过对比数值模拟和实测结果,验证数值模型的准确性和MJS管底土体加固措施的可行性。通过三维数值计算得出:采用MJS加固后的地表沉降、管线竖向位移、横向水平位移、弯矩和剪力比未加固土体分别减小53.59%、38.13%、73.3%、57.3%和48.02%,MJS能够明显提高管底土体承载力、密实度、强度和弹性模量,起到固定和保护管线的作用;进一步分析MJS的注浆置换率、加固宽度、加固深度对管线变形的影响,并给出置换率、加固宽度和加固深度建议值,为类似工程提供参考和借鉴。

A large cross-section rectangular pipe jacking construction is used at the 8^th entrance and exit of one station in Zhengzhou Metro Line 3, which needs to vertically underpass a DN2000 sewage pipeline in near distance. The soil under the sewage pipeline bottom is reinforced with MJS construction method. Real-time monitoring of surface and pipeline displacement during the pipe jacking process is carried out, numerical simulation is compared with actual measurement results, and the accuracy of the numerical model and the rationality of MJS pipe bottom soil reinforcement measures are verified, With the help of three-dimensional numerical calculations, it is found that the surface settlement, vertical displacement, horizontal displacement, bending moment and shear force of the pipeline with MJS reinforcement can be reduced about 53.59%, 38.13%, 73.3%, 57.3%, and 48.02% respectively compared to the unreinforced soil, and so MJS can significantly improve the bearing capacity, density, strength, and elastic modulus of the soil under the sewage pipeline bottom, and fix and protect the pipeline. Further analysis is conducted on the impact of grouting replacement rate, reinforcement width, and reinforcement depth of MJS on sewage pipeline deformation, and recommendations are provided about grouting replacement rate, reinforcement width and reinforcement depth, which provide reference and inspiration for similar projects.