胶层对内贴CFRP加固圆形隧洞受力特性的影响

Effect of Adhesive Layer on Mechanical Properties of Circular Tunnel Strengthened with CFRP

基于CFRP加固圆形隧洞的小比例尺模型试验,采用实体单元模拟胶层和衬砌混凝土,采用弹簧单元以及双线性界面黏结滑移关系模拟胶层和衬砌混凝土的弧形接触界面的黏结滑移行为,建立了"实体-弹簧-实体"三维有限元模型,并将有限元模型的计算结果与模型试验的实测结果以及界面应力理论计算结果进行了对比,验证了三维有限元模型的有效性.基于该有限元模型,着重分析了胶层厚度以及弹性模量的变化对混凝土应力、CFRP应力、胶层应力以及弧形接触界面复杂应力状态的影响.计算分析结果表明:胶层厚度以及弹性模量对隧洞衬砌混凝土的应力水平无明显影响,改变胶层的厚度以及弹性模量并不能明显地改善衬砌混凝土的受力状态;胶层的厚度以及弹性模量对弧形接触界面应力的影响十分显著,选择弹性模量较小的胶层,在施工过程中适当地减薄胶层的涂刷厚度,可以显著降低界面应力,从而减小内贴CFRP加固圆形隧洞结构发生剥离破坏的风险.

Based on the small scale model test of circular tunnel strengthened with CFRP,a “solid-spring-solid” three dimensional finite model is established. The adhesive layer and lining concrete is simulated by solid elements. The bond-slip behaviour of curved interface between adhesive layer and lining concrete is simulated by spring elements. The bilinear model is used to simulate the interfacial behaviour. Then,the calculation results of the finite element model are compared with the measured results from the small scale model test and the theoretical calculation results of interfacial stress,and the three dimensional finite element model is validated. Based on the finite element model,the effects of adhesive layer’s elasticity modulus and the thickness on the stress of concrete,CFRP, adhesive layer and the complex stress state of curved contact interface are investigated. The calculation and analysis results reveal that the thickness and elasticity modulus of the adhesive layer have little effect on the stress and strain of the lining concrete. Changing the thickness and elasticity modulus of the adhesive layer cannot improve the stress state of lining concrete. However,they have an obvious effect on the interfacial stress of the curved contact interface. A soft adhesive layer or a thin adhesive layer can reduce the interfacial stress,thus reducing the risk of debonding failure of circular tunnel strengthened with CFRP.