Abstract: Owing to the excellent shock absorption property of the foamed concrete, it can be used as a seismic isolation material for tunnels. In this study, a series of compression tests was conducted to study the effects of density, confining pressure and strain rate on mechanical properties of the foamed concrete. As the density increased, the failure mode of foamed concrete gradually changed from cell wall buckling to shear failure under the uniaxial compression condition. Besides, the strain-softening and material brittleness became more apparent after the peak. In addition, the strength and ductility of the foamed concrete increased with increasing confining pressure. Moreover, the property of foamed concrete transformed from a strain-softening to strain-hardening material. When strain rate increased in the range of medium strain rate (10?5/s～10?3/s), the strength of foamed concrete showed an exponential growth, and the residual stress in plastic range increased obviously. It was found that the effect of strain rate on the residual stress was greater with the increase of plastic strain. Based on the testing results, a new constitutive model was initially proposed for the foamed concrete. Then the numerical method was performed to investigate the effects of the shear modulus of isolation material, the thickness of isolation layer, and the properties of isolation interface on the isolation of Galongla tunnel. Therefore, the results can provide a helpful reference for the design of the related cushioning layer in tunnels with high intensity.

Key words: foamed concrete, strain rate, tunnel, isolation layer, interface