Research On Mechanical Properties Of Waterproof Membrane And Interface Between Layers Of Composite Shell Lined Tunnel

Composite shelled lined(CSL)structure is a kind of tunnel lining structure that sprays the waterproofing layer directly on the surface of the primary lining,then the primary and the secondary lining could be closely occluded.There are two key differences between it and the traditional lining structure: one is the using of double-bonded spray-applied waterproofing membrane;the other is that the load-sharing capacity of the interface between the primary and the secondary lining,which could improve the load efficiency of the lining structure.However,due to the the imperfection of research on the composite action of the primary and secondary lining brought by the double-bonded waterproofing membrane,there is still a lag in theory and design.To explore the load-sharing mechanism of the CSL structure,and to provide reasonable parameters for the lining design,the mechanical characteristics and damage mechanism of the interface and the waterproofing membrane of the CSL structure were studied.The main research contents and results are as follows:(1)The constitutive model of waterproof membrane and the damage models of interface were compared.The elastoplastic constitutive model,Mises strength criterion and cohesive zone model were selected to characterize the mechanical properties of waterproofing membrane and the interface respectively.(2)Uniaxial and multi-axial tensile tests were carried out on the polymer-modified waterproofing membrane.The failure law,stress-strain curve and constitutive parameters of waterproof membrane with different thickness under different tensile boundary conditions were obtained;the elastoplastic constitutive model was selected to establish the uniaxial tensile test simulation.The stress-strain curves were extracted and compared with the test results to verify the rationality of the test results and the simulation model.(3)The interface damage and evolution of CSL specimens were characterized based on cohesive zone model.The required interface parameters were obtained through interface bond and shear test.Combined with the finite element software,the interface shear tests were simulated to verify the test results and model parameters,and the influence of interface parameters on the mechanical properties of the specimens was explored.The results showed that the bilinear cohesive model could effectively deduce the interface damage process and failure law.(4)The normal stress of cross section of CSL beam was compared and analyzed,and the influence of interface parameters and membrane thickness on the mechanical properties of CSL structure was explored.The results showed that with the increase of interface parameters,the composite effect between primary and secondary lining would be more and more obvious.