Huayao Li

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.

Abandoned well pollution is a critical component of global environmental issues and a historical legacy issue of national development. Despite this, the specific mechanisms by which abandoned wells pollute groundwater remain unclear, particularly in the karst regions of Northern China, where no scientifically effective remediation methods exist. To address this gap, this study focuses on Yangquan City in Shanxi Province and employs field investigations, the analytic hierarchy process, high-definition deep-well logging technology, and qualitative analysis to assess the pollution risk of all abandoned wells in the study area, identifying those with high pollution risk. Through the analysis of extensive image and video data for these high-risk wells, we propose a conceptual model of cross-strata channels in abandoned wells and elucidate the mechanisms by which they pollute groundwater. The results show that, from a single-well perspective, the pollution mechanism is cross-strata pollution. From a regional perspective, the pollution mechanisms are hydraulic connectivity and solute migration and transformation. Based on these findings, we present a scientifically effective remediation strategy tailored to the typical characteristics of abandoned wells in the study area, offering a viable solution to the abandoned well pollution problem in Yangquan City. This research not only augments the theoretical framework in the domain of groundwater pollution but also advances sustainable groundwater security and management strategies. Moreover, the study furnishes theoretical foundations and pragmatic solutions for the remediation of abandoned wells in Yangquan City, which are crucial for the sustainability of the groundwater ecosystem.