Prediction of ultradeep pore water inflow in giant thick heterogeneous aquifers

Abstract

Objective The analytical solution model is computationally efficient and widely used to estimate aquifer surges. Analytical solution models are computationally efficient but involving many assumptions, such as that the aquifer is homogeneous, the amount of water pumped is constant, while the head loss in the well is ignored; these models are often referred to as homogeneous models. In fact, these assumptions are often not met, resulting in nonnegligible errors in the results, especially for heterogeneous giant thick aquifers.Meanwhile, the homogeneous model cannot estimate the permeability coefficient and water inflow of the broken zone, which is not conducive to solve the water problem during tunnel construction. Methods In this study, two pumping tests were carried out on the Shengli Tunnel Project in Tianshan Mountain, Xinjiang. A geological model was established based on comprehensive logging data and borehole data; a heterogeneous numerical simulation method was used to quantitatively investigate the amount of groundwater inflow in bore holes. The parameters in the rate determination model of the observation data of the first pumping test were used, and the rationality of the model and the postrate parameters were verified by the observation data of the second pumping test. Results The permeability coefficients of the fracture zone, intact granite and relatively intact granite were inverted and were 0.000 93 m/d, 0.000 5 m/d and 0.000 3 m/d, respectively. The total water inflow and the water inflow of the fracture zone were predicted to be 14.80 m3/h and 10.46 m3/h, respectively, of which the water inflow of the broken zone accounted for 70.676% of the total water consumption. Conclusion Field observations revealed head loss in aan ultradeepbore hole during pumping test. The heterogeneous numerical simulation model can explain the ultradeep hole pumping test data better than the homogeneous model, and the total water inflow calculated by the homogeneous model is 18.67 m3/h, which overestimates the water inflow. During tunnel construction, the hydrodynamic parameters and water inflow obtained by the heterogeneous model are more reliable.

Keywords

• aquifer
• heterogeneity
• pumping test
• groundwater
• ultradeep pore
• water inflow