This study employed an advanced elastoplastic constitutive model for sandy soil and fluid-solid coupling elements in ABAQUS to investigate the dynamic responses of soil-utility tunnel systems during seismic-induced liquefaction. By comparing the results of a free-field model, a single-tunnel-soil model, and twin-tunnel-soil models with simplified ground and input conditions, this study investigated the effects of soil-structure interaction and structure-soil-structure interaction (SSSI) on the development of liquefied zones and the impacts of tunnel spacing on the structural internal forces and displacement responses. Results indicate that the SSSI between adjacent tunnels significantly affects the dynamic responses of the structures and surrounding soil during liquefaction. When the spacing between adjacent tunnels is relatively small, the dynamic internal forces of the tunnels during liquefaction significantly increase compared with those in the absence of adjacent tunnels. In addition, the uplift and rotational displacements are high for adjacent twin tunnels. The amplification effects of internal forces and displacements caused by SSSI gradually diminish as the tunnel spacing increases. In the seismic design of utility tunnels accounting for liquefaction, the SSSI effects should be carefully considered if adjacent tunnels or other underground structures are present to avoid the underestimation of structural responses and corresponding safety risks.