Abstract:

 The headroom limit always restricts the crack treatment of tunnel secondary lining. Accordingly, ultrahighperformance concrete(UHPC) is proposed to replace ordinary concrete as a lining reinforcement material, and the feasibility and performance requirements of UHPC application are examined systematically. Based on the composite beam theory of dissimilar materials, the joint stress mechanism of a cracked lining and reinforced layer is studied. The relationship between the performance parameters of the reinforced material and the mechanical characteristics of the structure is obtained. Thus, the requirements of reinforcement layer thickness and the mechanical properties of UHPC are obtained. On this basis, a calculation method for converting between the stress and internal force of solid elements is proposed, and the stress characteristics of the joint surface between the lining and reinforcing materials are analyzed using a finite difference numerical simulation method. Consequently, the requirement of bond strength between UHPC and ordinary concrete is obtained. The results indicate the following: (1) For linings with a bearing capacity loss of less than 40%, UHPC can be used for reinforcement. (2) For linings with no more than 15% bearing capacity losses, UHPC can reduce the thickness of the reinforced layer to about 10 cm.

Key words: ultrahighperformance concrete, tunnel secondary lining, crack treatment, performance parameter