Abstract: The paper presents a calculation method of deep buried tunnel seismic response considering rock loosing zone cushioning effect. The basic train of thought is considering strength decrease of surrounding rock, cushion effect after rock loosing and fracture and wave transmit around the loosing zone. Reduction factor R is used to calculate the seismic response. Theoretical solution of lining structure uniform to surrounding rock movement is given , based on which, a calculation method considering rock loosing zone damping effect is deduced, taking S wave as an example. FLAC3D dynamic module is used to make numerical simulation of loosing zone damping effect. The results are compared with theoretical solution of lining structure uniform to surrounding rock movement and reduction factor method. Conclusions are: When loosing zone is fully taken into account, the result of reduction factor R method is coinciding with numerical simulation result (Maximum error value of bending moment is 8.28%, maximum error value of shear force is 10.68%), more accurate than theoretical solution of lining structure uniform to surrounding rock movement (Maximum error value of bending moment is 62.13%, maximum error value of shear force is 50.49%). The train of thought and concept of this method is clear, with concise formula and less calculation , and easy to practical application.

Key words: Seismic response, Deep buried tunnel, Loosing zone, Damping effect