This article examines the tunneling process for constructing subway shields in cities aiming at preventing the risk of water and mud inrush in fault fracture zones and with abundant groundwater. Here, we studied the influence law and the response sensitivity of shield cutter heads with different types and diameters on the critical safety distance. Likewise, we reveal the influence law and response sensitivity of the front fault fracture zone with different thicknesses and water pressure on the critical safety distance. This study simulates the propulsion process of shield tunnels and the moment of water inrush using COMSOL Multiphysics fluid–structure coupling method. Using a numerical simulation of a three-dimensional finite element model, we obtained a formula for a critical safe distance for the fault fracture zone in front of the shield tunnel. This research has particular relevance to the construction of metro shield excavations in cities with fault fracture zones and abundant underground water.