<p>This study presents a numerical investigation into the effect of the tunnel located within a normal fault zone on the fault-foundation interaction. The impacts of various parameters–including foundation location, tunnel burial depth, the tunnel’s position relative to the fault line, tunnel diameter, tunnel rigidity, and tunnel cross-sectional shape–were evaluated. The tunnel led to increased foundation rotation, thereby elevating the risk of instability in the surface structure. Findings demonstrated that expanding the burial depth of subsurface structures could improve the performance of surface structures. Increasing the tunnel diameter altered the distribution of fault rupture in the soil due to the larger void space, and in certain cases, it amplified foundation rotation. Numerical simulation confirmed that the tunnel rigidity has no significant impact on the mechanisms governing fault–foundation interaction. Doubling the tunnel lining thickness reduced the maximum lining stress by an average of approximately 60%. The geometry of the tunnel cross-section influenced the mechanical behavior of the tunnel lining. Maximum stresses in the lining were lower for square tunnels. The results indicated that the patterns of foundation rotation and fault rupture in square and horseshoe tunnels were generally similar to those observed in circular tunnels.</p>