Effectiveness of Advanced Support for Shallow-Buried Tunnel Excavation Under-Crossing Provincial Highway in Water-Rich Fractured Zone

To address the safety control challenges of shallow-buried tunnels under-crossing provincial highways in water-rich fractured zones,this study took the Genzi Tunnel project (C1 section) of the Guangdong Water Resources Allocation Project in the Beibu Gulf Metropolitan Area as a case study. Numerical simulations and field measurements were employed to investigate the advanced support using small conduits and pipe sheds,and the effectiveness of three advanced support schemes was analyzed: small conduits alone,pipe sheds alone,and combined small conduits with pipe sheds. The findings show that ① The fluid-solid coupling numerical model effectively simulates and predicts the support process during the construction of shallow-buried tunnels under-crossing provincial highways in water-rich fractured zones. ② Dual support and pipe shed support schemes can effectively reduce and control surface subsidence compared to the small conduit scheme. ③ The arching effect generated by pipe sheds induces substantial stress concentrations during initial support at the vault springing of outermost pipe shed elements. Therefore,it is necessary to consider the adverse effect of the possible stress concentration on the initial support force when arranging the support scope of the pipe shed. The dual support scheme integrating pipe sheds and small conduits proves effective in ensuring safety during the construction of tunnels under-crossing provincial highways.