富水砂层中盾构始发穿越既有地铁线路的结构稳定性研究

Study on Structural Stability of Shield Launching and Crossing Existing Metro Line in Water-rich Sandy Stratum

[目的]富水砂层地质条件下,新建地铁线路盾构始发穿越既有地铁线路时,对既有地铁线路结构稳定性的研究较为鲜见,需总结类似工程的相关规律。[方法]以新建的郑州地铁7号线黄河迎宾馆站—英才街站区间盾构始发穿越既有地铁2号线结构工程为依托,根据实际工况采用有限元软件MIDAS GTS NX建立了施工区间的三维数值模型,并利用软件的结果提取功能得到了该工程对应模型的模拟结果。选取现场2个监测点位,将2个测点的现场实测值与模拟计算值进行对比,证实了该模型的准确性。在此基础上,进一步研究了盾构始发穿越、一般下穿施工两种穿越方式下对既有地铁线路结构稳定性的影响,以及始发洞门与既有地铁结构间竖向距离d的4个取值对既有地铁线路结构稳定性的影响。[结果及结论]所建三维模型在一定程度上可反映实际工况。在既有地铁线路结构、材料、加固方式等因素均不变的情况下,既有地铁线路结构的稳定性因穿越方式的不同而有所差异,与一般下穿施工相比,采用盾构始发下穿方式时对既有地铁线路结构的影响较小。采用盾构始发下穿方式时,d的取值不同,对既有地铁线路结构稳定性的影响有较大差异。d=2.00 m对既有地铁线路结构的影响较小,工程成本也较小。建议在工程条件允许下采用盾构始发下穿方式,且推荐d值取2.00 m。

[Objective]In geological conditions with water-rich sandy stratum,research on the structural stability of existing metro lines with new metro line shield launching crossing is relatively scarce.It is essential to summarize relevant patterns for similar projects.[Method]Leveraging the structural engineering of shield launching crossing the existing Line 2 at Huanghe Yingbinguan Sta.-Yingcai Road Sta.interval on Zhengzhou Metro Line 7 as basis,according to actual working conditions,a 3D numerical model of the constructed interval is established using finite element software MIDAS GTS NX,and simulation results for the project corresponding model are obtained using the software result-extraction function.Two monitoring points are selected at the site,and the field-monitored values of them are compared with the simulated values to confirm the model accuracy.On this basis,the influence on existing metro line structural stability under shield launching and conventional under-passing two tunneling methods are further studied.The influence of four values of the vertical distance d between launching portal and existing metro structure is explored.[Result&Conclusion]The established 3D model,to a certain extent,reflects the actual working conditions.Keeping factors such as the structure,material,and reinforcement method of the existing metro line unchanged,the structural stability of existing metro line varies depending on the tunneling methods.Compared to conventional under-passing construction method,the shield launching crossing causes less influence on the existing metro line structure.When this method is adopted,different d values cause different degrees of impact on existing metro line structural stability.In the case of d=2.00 m,its influence on existing metro line structure is minimal,and the engineering cost is relatively low.It is recommended to adopt shield launching under-passing method under permissible engineering conditions,and the suggested value is d=2.00 m.