Dynamic interaction of two circular lined tunnels with imperfect interfaces under cylindrical P-waves

A semi-analytical method is used to characterize the interacting effects of imperfect interfaces around two circular lined tunnels under cylindrical P-waves. The spring interface model separating the tunnels from the rock mass is introduced to analyze the interface effect. To express the wave fields in different regions, the wave function expand method is applied, and the expanded coefficients are determined by satisfying the boundary conditions with imperfect interface effect. The dynamic stress concentration factors around the tunnels are evaluated and analyzed. The effects of incident wave's frequency, imperfect interface conditions and the distance between the two tunnels are examined. It is found that the imperfect interface effect increases significantly due to the interaction between the two tunnels, especially at the positions adjacent to another one. The high-frequency loading leads to a lower dynamic stress; however, the interacting effect is greater. The imperfect interface effect will increase significantly due to the interaction between the two tunnels. The imperfect interface effect at different positions of tunnels is also examined.