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Abstract The construction of rock tunnels usually causes the decline of the surrounding groundwater level and damage to the groundwater balance in the sensitive area. However, due to the over-simplification of the model and scarcity of data, it is very difficult for common approach to consider the spatial variability of hydrogeological parameters of the rock mass in study area. In order to solve the above problems, this paper adopted a Bayesian approach with the goal of deriving the posterior distributions of the dependent variables conditional on local data. The Bayesian multi-source data fusion technique is used to determine the prior distribution of rainfall infiltration coefficient and rock mass hydraulic conductivity. Finally, MODFLOW model is used to establish a 3D numerical model that can reliably represent the spatial variability of hydrogeological parameters of the rock mass in the study area. In conclusion, the calculation result matches well with measured values.
1 Instructions With the growing environmental awareness in the society, the issue of groundwater environmental protection in the construction of tunnels in rock masses has received increasing attention (Fongfl et al., 1998; Liu et al., 2015). On the one hand, groundwater is an important cause of tunnel disasters (Tang et al., 2011). The water inflow from the tunnel soaks and softens the soft structures and soft layers of the surrounding rock and the fracture zone, Hence, the strength is reduced, and the small filler between the weak surfaces is taken away, causing the rock mass to disintegrate. This eventually led to landslides (Goodman et al., 1965). The problem of the gushed water and water leakage during tunnel construction and operation period will delay the construction period and increase the construction cost, which will lead to major safety accidents such as casualties (Yan, 2018). For example, in the 415 tunnels of the Nankun Railway, 93% of the construction sections have had gushed water; on the other hand, the water in the rock tunnel will also cause water loss, water level decline, deterioration of ecological environment, and adverse consequences of surrounding household water (Liu et al., 2015; Liu, 2015). For example, the construction of the No.1 tunnel in Jiugong Mountainous Area Reservoir caused many gullies and springs to be dried up or reduced in water volume, and caused large ground subsidence. The hydrogeological environment system in the tunnel site was damaged and people's lives were seriously disturbed.
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