Experimental and Numerical Study on Shield Tunnel Strengthened by Ultra-high Performance Concrete

Abstract:

Based on the application of ultra-high performance concrete （UHPC） in the shield tunnel strengthening， the steel plate-UHPC reinforced structure of shield tunnels was proposed. Steel plates were utilized as the inner linings of shield tunnels， with UHPC filling between steel plates and segments. Planting reinforcing bars， chemical anchors and struts served as the interface connectors， forming a community capable of withstanding external load. By conducting the full-scale ultimate load test and establishing the nonlinear numerical model， the failure mechanism of the reinforced structure was investigated， and key factors affecting the reinforcement performance were analyzed. The results indicate that the failure mode of the reinforced structure exhibits superior ductility characteristics. The stiffness of the reinforced structure is primarily dominated by the stiffness of the segments and the reinforcement， while the bearing capacity of the reinforced structure is crucially influenced by the strength of segements， and the ultimate bearing capacity increases by 28% compared to the structure only reinforced by UHPC. In the event of the limit state， a few steel plates located at the top and waist of the structure yield， with main reinforcements yielding in tension. The numerical parameter analysis demonstrates that the performance indexes of the reinforced structure are significantly influenced by the thickness of reinforcement layers and the bonding performance of interfaces. Consequently， it is recommended that the thickness of the steel plate be increased and that the interface connectors be secured.

Key words:tunnel engineering;shield tunnel;strengthening;full-scale test;ultra-high performance concrete （UHPC);ultimate bearing capacity