Study on the Transient Responses of Composite Lining Tunnels Subjected to Blasting P-Waves and SV-Waves

Based on wave dynamics theory, wave function expansion methods are used in this paper to derive the analytical solution for the scattering of plane P-waves and SV-waves in a composite lining tunnel within an infinite medium. The transient analytical solution for the composite lining tunnel under plane blasting P-wave and SV-wave disturbances is obtained by introducing the [[EQUATION]] function, the Heaviside step function, and Fourier integral transforms. The effects of the incident wave type, wavelength, and shear modulus ratio on the tunnel's transient dynamic stress concentration factor (DSCF) are discussed, and "soft outside, rigid inside" damping measures are proposed. The results show that transient P-waves and SV-waves with short wavelengths cause significant dynamic stress concentration in the tunnel lining and that the influence of transient SV-waves is more critical. The peak value of the dynamic stress concentration coefficient (MaxDSCF) is more prominent in the arch and arch bottom regions, but the wavelength has little effect on the distribution of MaxDSCF. By implementing the structural design of "soft outside, rigid inside" and optimizing the thickness of the initial support, the dynamic stress concentration can be effectively reduced, thereby achieving effective shock absorption.