A karst groundwater system ranks among the most sensitive and vulnerable types of groundwater systems. Coal mining and tunnel excavation can greatly change the natural hydrogeological flow system, groundwater-dependent vegetation, soil, as well as hydrology of surface water systems. Abandoned coal mine caves and proposed highway tunnels may have significant influences on groundwater systems. This study employs MODFLOW, a 3D finite-difference groundwater model software, to simulate the groundwater system's response to coal mining and tunnel excavation impact in Zhongliang Mountain, Chongqing, from 1948 to 2035. The results show a regional decline in groundwater levels within the study area following mining and tunnel construction. The groundwater flow system in the study area evolves from the Jialing River groundwater flow system to encompass the Jialing River, Moxinpo highway tunnel, Moxinpo, and the Liujiagou coal mine cave groundwater flow systems between 1948 and 2025. With the completion of tunnel construction, the groundwater level at the top of the tunnel is gradually restored to the water level in the natural state. The model also predicts groundwater level variations between 2025 and 2035. The groundwater level will rise further initially, however, it may take about 10 years for the system to stabilize and reach a new equilibrium. In light of these findings, it is advised that changes in groundwater flow systems caused by tunnel construction should be modeled prior to the practical construction. This approach is crucial for evaluating potential engineering and environmental implications.

At present, most calculation results regarding foundation pit dewatering are ideal values, making construction resources prone to being wasted. In order to optimize the traditional pipe well design of large wells, the linear programming solution module in Excel is used, with the total water inflow taken as the objective function, the water level drawdown used as the constraint and test condition, and a station project on the Chengdu Metro Line 7 serving as the subject of this study. The total water inflow of the traditional pipe well design is optimized by the simplex method, producing a total water inflow of 4040.65 m³/d, which, compared with 4829.79 m³/d, the total water inflow calculated by means of the traditional design optimization method, engenders a reduction of roughly 16% per day. The feasibility of the optimization methodology is verified by the drawdown constraint, which reveals the decrease of construction costs and the diminution of the influence that the lowered groundwater level has on the surroundings of the metro station. Finally, references are provided as to optimizing the dewatering designs for other metro stations in similar engineering and hydrogeological conditions.