An urban road collapse has become one of the significant geohazards frequently occurring in metropolitan cities worldwide. In most cases, these devastating superficial collapses are known to be induced by small underground cavities. They are created by the failure of subsurface structures and pipelines (e.g., water supply/sewer lines, subway tunnels). However, the cavity generation and expansion process, interacted by intense precipitation, groundwater movement, and subsurface geologic environment, is not yet fully understood. This study aims to understand the mechanism of cavity initiation and expansion using a numerical model coupling groundwater flow, poroelastic deformation, and internal soil erosion. The model is then applied to road collapse cases by a damaged sewer line failure and internal erosion. Effects of the precipitation rate and period on internal erosion are also investigated to predict potential risks for road collapse. Numerical simulation results show that the underground cavities are closely related to the focused groundwater flow by the leakage through an opening in the damaged pipeline. Internal erosion accelerates the removal of fine soil particles and creates collapsing-susceptible vacant areas. The results also show that intense precipitation in a short interval exerts the most damaging effects on the subsurface stability comparing other scenarios with less severe and continuous rainfalls.