Abstract:

The large crosssectional tunnel group on Hubei Section of ZhengzhouWanzhou Highspeed Railway has the features of large excavation crosssection, high proportion of weak surrounding rocks and large scale mechanized construction. Firstly, field monitoring on the displacement of primary support is carried out. And then the monitoring data are classified, summarized and analyzed to obtain the functional expressions for primary support displacement along longitudinal direction and proportions of tunnel displacement along longitudinal direction of each section under different conditions of large crosssection methods (fullsection method and microbench method), different buried depth (deep buried and shallow buried) and different grades of surrounding rocks (Grade Ⅳ and Ⅴ). Finally, the recommerded values of the primary support displacement control criterion for large scale mechanized construction of tunnels on ZhengzhouWanzhou Highspeed Railway are proposed based on the ultimate displacement in Technical Specification for Monitoring Measurement of Railway Tunnel: Q/CR 92182015. The results show that: (1) The displacement control criterions according to the distance from tunnel face in different phases of tunnel on ZhengzhouWanzhou Highspeed Railway are variable under different conditions, thus the standard ultimate displacement in criterion is unreasonable. (2) The laws of crown top settlement and tunnel surrounding horizontal convergence are consistent under different conditions of surrounding rock grades, buried depths and excavation methods.

Key words: ZhengzhouWanzhou highspeed railway tunnel, large crosssectional tunnel, fullsection method, microbench method, mechanized construction, primary support, deformation control criterion, monitoring measurement