An isolation layer is one of the countermeasures to promote the anti-seismic performance of tunnels. A newly invented polymeric material, non-water reacted two-component polymeric material (NRTCPM), is superior in impermeability and construction efficiency. In this study, covering a tunnel with NRTCPM coating to mitigate the damage caused by an earthquake is discussed, and an Impact Resonance Test (IRT) is firstly used to obtain the damping ratios and dynamic elastic modulus of NRTCPM. By using infinite element boundary, eight dynamic numerical modelsare made to study the isolation effects based on different density, Poisson’s ratio, dynamic elastic modulus and thickness of isolation layer values. Three different conditions are explored in this paper, namely (1) no NRTCPM layer coating around tunnel; (2) different densities, Poisson’s ratios and dynamic elastic moduli of a polymeric layer; and (3) various thicknesses of polymeric isolation layers around the lining. Tensile and compressive stresses are compared under these different conditions. The results show that retrofitting tunnel lining with this material has a good effect on seismic isolation. An optimum density and thickness of the NRTCPM layer is suggested considering cost and strength.
Proposal of a Seismic Isolation Structure for Urban Tunnels and the Method to Evaluate Its Isolation Effects.
