Experimental research on the mechanical behavior of segmental joints of shield tunnel reinforced with a new stainless steel corrugated plate

Shield tunnels are inevitably damaged by complex diseases during operation, so repair and reinforcement are essential. The stainless steel corrugated plate (SSCP) has many advantages for tunnel structure reinforcement because of its high strength, lightweight, convenient construction and installation, and corrosion resistance. Mechanical behaviors of an unreinforced segmental joint and a segmental joint reinforced with a new SSCP were investigated by full-scale tests. The reinforcement test took into account the actual reinforcement conditions in the field, i.e. the joint bore the load alone before reinforcement, maintained the load during reinforcement, and bore the load together with the SSCP after reinforcement. The experimental results demonstrate that: (1) both unreinforced and reinforced joints exhibit a compressive-flexural failure mechanism, and their failure is manifested by concrete crushing in the compressed zone of the joint. (2) Compared to that unreinforced joint, the bending moment and ultimate vertical load of the reinforced one are increased by 73.7% and 119.3%, respectively. And the reinforced joint is stiffer than the unreinforced one, reflecting that SSCP reinforcement enables higher stiffness. (3) Trends of strain-moment curves of the bent bolts and concrete are similar in the unreinforced and reinforced joints. Under the same load, the strains in the reinforced group are smaller than those in the unreinforced group, indicating that the SSCP in the reinforced group shares the load. (4) The strains of the SSCP exhibits a symmetrical distribution in the length direction with the joint section as the symmetrical plane. The strains at the trough show tensile strain, while the strains at the crest show compressive strain. The combined force of the corrugated steel plate cross-section is tensile (i.e., SSCP shares the tension load in the tensile zone of the joint), reflecting the reinforcement effect of SSCP.