Geological, Tectonic, and Lithological Evaluation Approach of the Fault Hydraulic Conductive Property

The hydraulic characteristics of faults are of great significance for groundwater transport. Many groundwater inrush disasters are caused by hydraulically conductive faults. However, the hydraulic conductive property of a fault is complex and varies in different parts, and evaluation in coal mines has always been a hard challenge for hydrogeologists. An evaluation model proposed by Li et al. partially solves the above-mentioned problem [Li L. N.Nat. Resour. Res.2022, 31, 849-865]. However, this model has two shortcomings: (1) They focused only on small faults and did not have a specific method for large faults with a drop of more than 100 m. (2) The problem of differences between different locations of the same fault is not solved. This paper presents a method to estimate the fault hydraulic conductive property using abundant geological exploration data without hydrologic tests. First, the influence of fault rocks, water pressure, and geostress on the fault hydraulic conductive property was analyzed. Moreover, four evaluation indices, namely, the fault shaliness index (FSI), mudstone deformation index (MDI), fault rock plugging index (FRPI), and water pressure index (WPI), were proposed, and evaluation criteria were established to divide the fault hydraulic conductive property into five grades. This method was applied in Shandong Province and verified by hydrochemical experiments, surface boreholes, injection tests, and geophysical data. Furthermore, the method may be transferable to other coal mines with similar geological and hydrogeological characteristics.