Quantitative Analysis of Hydraulic Conductivity of Coal Measure Strata in Changzhi Basin, China, Using Staged Water Injection Tests

The serious shortages and destruction of groundwater resources caused by coal mining, especially group mining, is a major hurdle for the sustainable development of the mining economy, resource management, and preserving the environment that urgently needs to be addressed. Large efforts have been made to protect the groundwater resources affected by coal mining but they have had little effect. The difficulty and uncertainty in investigating the structural changes in roof strata and the relationship between the roof rock fissure formation rate and hydraulic conductivity are the main obstacles hindering the investigation, assessment and management of groundwater resources in roof strata. In this study, we tackled this problem by performing water injection tests in ground surface boreholes and underground boreholes in the roof strata, and pumping tests in wells over the goaf. Clear differences in hydraulic conductivity changes in the collapsed roof strata were observed. These observations provide valuable information on changes in groundwater flow and the distribution of collapsed and fissured zones. The pumping tests also revealed an increase in hydraulic conductivity in the subsidence basin of Quaternary deposits over the goaf. This increased hydraulic conductivity is useful for the assessment of groundwater resources and the prediction of single-well water yields.