Abstract
To better protect the ecological environment during large scale underground coal mining operations in the northwest of China, the authors have proposed a water-conservation coal mining (WCCM) method. This case study demonstrated the successful application of WCCM in the Yu-Shen mining area. Firstly, by using the analytic hierarchy process (AHP), the influencing factors of WCCM were identified and the identification model with a multilevel structure was developed, to determine the weight of each influencing factor. Based on this, the five maps: overburden thickness contour, stratigraphic structure map, water-rich zoning map of aquifers, aquiclude thickness contour and coal seam thickness contour, were analyzed and determined. This formed the basis for studying WCCM in the mining area. Using the geological conditions of the Yu-Shen mining area, the features of caved zone, water conductive fractured zone (WCFZ) and protective zone were studied. The equations for calculating the height of the “three zones” were proposed. Considering the hydrogeological condition of Yu-Shen mining area, the criteria were put forward to evaluate the impact of coal mining on groundwater, which were then used to determine the distribution of different impact levels. Using strata control theory, the mechanism and applicability of WCCM methods, including height-restricted mining, (partial) backfill mining and narrow strip mining, together with the applicable zone of these methods, were analyzed and identified. Under the guidance of “two zoning” (zoning based on coal mining’s impact level on groundwater and zoning based on applicability of WCCM methods), the WCCM practice was carried out in Yu-Shen mining area. The research findings will provide theoretical and practical instruction for the WCCM in the northwest mining area of China, which is important to reduce the impact of mining on surface and groundwater.
Highlights
In China, coal resources are mainly distributed in the north and west, especially in the provinces of Shanxi, Shaanxi, Inner Mongolia, and Xinjiang, which account for about 70% of all Chinese coal reserves
The location of top boundary and height of water conductive fractured zone (WCFZ) induced by mining of each main seam in Yu-Shen mining areaboundary were determined observation drilling fluid lossseam combined
Based on field observations and the numerical simulation results shown in Tables 2 and 5 respectively, four equations for predicting the height of WCFZ were obtained by regression analysis using different stratigraphic structures in Yu-Shen mining area:
Summary
In China, coal resources are mainly distributed in the north and west, especially in the provinces of Shanxi, Shaanxi, Inner Mongolia, and Xinjiang, which account for about 70% of all Chinese coal reserves. We analyzed the factors affecting WCCM in Yu-Shen mining area (part of Shaanbei coal production base), and proposed a systematic WCCM method based on “five maps, three zones, and two zoning plans”, which would systematize and standardize WCCM research and practice, providing guidance on how to achieve WCCM in Northwest China.
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