<p>The tunnel construction process introduces imperfections in the interface between the tunnel liner and the surrounding soil/rock. These imperfections must be accounted for to understand the seismic behavior of tunnels fully. In this study, a semi-analytical solution is developed for the 3D seismic response of a shallow tunnel with an imperfect interface when subjected to compressive waves and shear waves incident on the tunnel from arbitrary directions. A parametric study is then conducted using this semi-analytical solution to understand the effect of interface conditions and incident wave parameters on the tunnel/ground response. These parametric studies provide insights into the conditions at which the perfectly bonded interface approximation serves as a conservative estimate for the seismic response of the tunnel.</p>