In conventional composite tunnel linings,the initial support and secondary lining each share a portion of the sur-rounding rock pressure.However,field monitoring indicates that the initial support often bears the majority of the load,leav-ing the sturctural safety of the design unverified.Based on the Xiangshan Tunnel of the Zhongwei-Lanzhou Railway,this study proposes an optimized composite lining scheme whereby the initial support is designed to carry 100%of the load,and secondary lining functions as a safety reserve.A test section was constructed on-site to evaluate the structural performance and safety.The results show that the optimized initial support structure stabilizes approximately 20 days after installation,and both Ⅳa and Ⅴa support systems remain safe and reliable.Furthermore,a comparative analysis reveals enhanced construction efficiency and re-duced consumption of support materials under the optimized design.Therefore,the optimized composite lining,in which the in-itial support serves as the primary load-bearing element,proves to be a safe and feasible approach.
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