Groundwater Level Under Tunnel Step Excavation by Area Well Method

With the increase in the number of tunnel engineering constructions in mountainous areas, problems such as groundwater loss and ecological damage have gradually emerged. Therefore, based on the area well method, a water inflow prediction method considering the construction process of the step method was established. The influence of factors such as the tunnel permeability coefficient, geometric dimensions and construction progress on the groundwater level were further studied. The results show that the water inflow at different construction stages is more sensitive to different parameters, the factors that has the greatest impact on the water inflow throughout the entire tunnel construction is the thickness and permeability coefficient of the first lining, which affect the water inflow of the three stages (from stage 2 to stage 4). Moreover, to control the maximum water inflow throughout the entire tunnel construction, it is necessary to first ensure that the permeability coefficient of the lining can stabilize the groundwater level (at least 3×10-6 m/d). Secondly, the construction speed of the stage 1 and stage 3 should be as fast as possible, and a reasonable construction speed can reduce the decrease in the groundwater level by at least 42.5%.