Abstract
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.
Highlights
The seismic response mitigation and seismic protection of structures have been discussed in recent decades [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
The results show that retrofitting tunnel lining with this material has a good effect on seismic isolation
The seismic isolation effect of a rectangular-shaped tunnel was investigated by Shimamura et al (1999)
Summary
The seismic response mitigation and seismic protection of structures have been discussed in recent decades [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. Coating with soft seismic isolation materials has been studied by many researchers. Kim and Konagai (2000), Kim and Konagai (2001), and Konagai and Kim (2001) showed that materials with a low Poisson’s ratio and a low shear modulus were preferable for enhancing the seismic efficiency of an isolation layer. They studied the influence of key material properties, such as the reduction factor (TFcoat /TFuncoat ), on the seismic isolation effect. Kiryu et al (2012) used a polymer isolation method to reduce the seismic effect on the tunnel, and the influences of shear stiffness and thicknesses of soil covering the tunnel were studied [6]. Zhao et al (2013, 2018) and Ma et al (2018) retrofitted the tunnel with foamed concrete, andthe subsequent effectiveness of seismic isolation was evaluated by both
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