Comprehensive Evaluation of Hydrogeological Impact of Tunnel Construction in Karst Aquifers by 3D Numerical Simulations and Water Balance Models

Underground engineering activities such as tunnelling are commonly involved in large-scale hydraulic and hydropower projects. In karst regions, tunnel engineering often encounters geological disasters such as water inrush and ground collapse. Water discharge during tunnel construction can also strongly disturb the karst groundwater systems. The above issues require a comprehensive evaluation of the hydrogeological impact of tunnel engineering. In this study, we adopted both a 3D numerical approach based on coupled discrete-continuum models and a modified lumped-parameter water balance model to comprehensively evaluate the hydrogeological impact of tunnel engineering during implementation of the Jiayan Water Diversion Project in Guizhou Province. In the numerical approach, a high-resolution 3D model was built to quantitatively evaluate the spatial and temporal characteristics of the tunnel construction impact on a karst groundwater system. It was shown that during construction, the groundwater drainage through the tunnels accounted for about 11% of the total groundwater discharge in the studied area. The total discharge through karst conduits decreases by about 30% in response to the tunnel construction. Meanwhile, the lumped-parameter water balance model provided an avenue for fast evaluation the impact of tunnel construction on the discharge from the aquifer system. The discharge through the spring and tunnels evaluated by water balance model are in good agreement with the results of the numerical model. On a whole, our work demonstrates the use of different modelling approaches to study karst groundwater flow affected by tunnel engineering that can be of values for different stages of an engineering project.