Seepage Characteristics of a Single Ascending Relief Well Dewatering an Overlying Aquifer

Wenxue Wang,Tong Jiang,Jinyu Dong,Boris Faybishenko,Yang Li

doi:10.3390/w12030919

Abstract

The application of groundwater relief, i.e., dewatering, ascending wells, drilled upward from the mining tunnel into the overlying aquifer, is common in underground mining engineering. In this study, the seepage characteristics of single ascending partially and fully penetrating relief wells are investigated using a series of laboratory sand-tank experiments and numerical simulations. The seepage characteristics of ascending wells dewatering an overlying aquifer are different from those of conventional pumping wells descending from the ground surface into the underlying aquifer, because of the pronounced influence of the seepage face boundary condition along the seepage boundary of the ascending dewatering well. The seepage face of the ascending well is formed as the well casing remains open and water is discharged under the action of gravity through the well casing. The results of laboratory sand-tank experiments and modeling show that when the degree of penetration of an ascending relief well does not exceed a critical value, the effect of the seepage face cannot be ignored. In particular, the seepage flux increases as the degree of penetration increases following an exponential function, and the relationship between the seepage flux and the well radius can be described using a power law function. The results of numerical simulations are used to develop a series of type curves to evaluate the effects of the critical degree of penetration for different well radii and different aquifer water levels. Modified versions of the Dupuit and Dupuit–Thiem formulae for a single ascending partially well for the degree of penetration less than the critical one for the unconfined, confined, and confined-unconfined aquifers are developed.

Highlights

Construction of many underground facilities and tunnels, deep foundation pits, and underground coal mines, which may be affected by underground water intrusion, require dewatering of an overlying aquifers [1,2,3,4,5,6,7,8,9,10,11]
The seepage fluxes Qr1 for the fully penetrating well of radius r1 = 1 cm and 1 m, which were calculated for the case of complete drawdown, were used to determine the dimensionless seepage fluxes given by
The seepage characteristics of the ascending relief wells” (ARWs) are affected by the seepage face boundary condition along an outflow boundary of the ARW, because the interior of the well casing remains open to the ambient air and is affected by the atmospheric pressure, so that water is discharging under gravity through the open bottom of the well casing

Summary

Introduction

Construction of many underground facilities and tunnels, deep foundation pits, and underground coal mines, which may be affected by underground water intrusion, require dewatering of an overlying aquifers [1,2,3,4,5,6,7,8,9,10,11]. A common method to reduce the groundwater level to prevent inundation of underground excavations is the use of water pumping wells, which are drilled from the land surface into the aquifer [5,7,8]. Another method applied in the mining industry for dewatering and depressurization of overlying aquifers is to drill dewatering wells from the underground mines’ tunnels upward into the overlying aquifer [1,11,12,13,14,15,16,17,18,19].

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