STUDY ON THE LOAD SHARING RATIO OF THE SECONDARY LINING IN LARGE-SECTION COMPOSITE LINING TUNNELS
To better analyze the load formation mechanism of the primary and secondary linings in large-section tun-nels with composite linings and the load-sharing ratio of the secondary lining,and to provide reference for the design of large-section tunnel lining structures,this paper relies on the Chengzai mountain tunnel project of the Shenshanxi expansion project.Using FLAC3D,different construction calculation models of large-section tunnels under various burial depths were established to study the load-sharing situation of large-section tunnels with Va-grade surround-ing rock under the double-side wall guiding method.The results indicate that the load-sharing ratio of the secondary lining in large-section tunnels generally does not exceed 50%,indicating that the secondary lining is not the primary load-bearing structure.The correlation between the secondary lining load-sharing ratio and burial depth is low;how-ever,the magnitude of the load borne by the secondary lining is related to the burial depth.The deeper the burial,the higher the initial load,and the more significant the increase in the secondary lining load-sharing ratio.After its con-struction,the secondary lining starts to bear loads,with the load on the secondary lining increasing rapidly.After the support structure stabilizes,the load variation curve of the secondary lining tends to stabilize.The vertical load on the tunnel crown is generally greater than the transverse load on the sidewalls,and the load-sharing ratio of the second-ary lining at the crown is also generally higher.For large-section tunnels in weak surrounding rock segments,it is ad-visable to enhance the stiffness of the primary lining to reduce the load borne by the secondary lining.The findings provide reference for the optimization design of large-section tunnel support structures.
large cross-section tunnelnumerical simulationload sharing ratio of secondary liningsecondary lin-ing pressure