Meitan xuebao (Oct 2023)
Analysis method of mining seepage field
Abstract
Aquifer protection in high-intensity coal mining is difficult to green and safe-mining, due to less knowledge of the response law of local seepage-flow in the mining area after aquifer damaged for the protection method and techniques. Adopting the coupling analysis idea of local multi-field source, the study focuses on the response law of mining-seepage field and aimed to revel coupling relationship between locally mining and the seepage field response and construct local mining groundwater system used to analyze the time-space evolution law of mining-seepage field and its cumulative effects, with the limited hydrological data including ground and underground observation. Based on application analysis of typical case, the analysis method of mining-seepage field is pro-posed, suitable for groundwater protection and engineering restoration in the mining area. The results show: ① Based on coupling relation of “mining excitation-overburden strain-seepage field response” and the energy transfer relationship from mining kinetic and seepage potential energy, the mining-seepage coupling mechanism is proposed. The mining seepage system (MSS) is constructed for describing the state of the operative local seepage field being divided into conduction zone, disturbance zone and radiation zone; ② The simplified mining-seepage effect models are established, including the “columnar seepage model” of the conduction zone and the “well-seepage” state model of the disturbance-radiation zone. Relative analyzing parameters are proposed, such as the miming-seepage coupling coefficient, the mining-seepage flow, the apparent water conductivity, distance of source-measuring point for describing statues of mining-seepage field, and aquifer damage, the risk of water-reserving safe-mining and mining height used for the groundwater protection analysis; ③ Revealed that the mining-seepage coupling coefficient is the key factor affecting the characteristics of the local mining-seepage response, featured that the hard rock overburden is larger than soft rock in coupling strength and influence range, and that the low-conductivity aquifer is narrower than high-conductivity in mining seepage field response area, higher in the response frequency and closer in the cumulative influence distance. Timing variation of mining-seepage flow and the water conductivity are characteristics of the periodicity, amplitude fluctuation and in-rush-flow pulsation of the reactive response; ④ Based on mining-seepage coupling cumulative effect, the identification process of the conduction area is proposed, containing the equilibrium analyzing method for“suppling, run-off, excretion”of mining area and the constraint-equilibrium method for induced-seepage flow of the mining face. Analysis method of overburden thickness, mining risk and mining height proposed, aimed to control mining damage of heterogeneous aquifer; ⑤ The application indicates that the mining-seepage disturbs directly the III aquifer and affects the II aquifer, and the cumulative impact range exceeds respectively 2 km and 6 km, during mining period (2012–2019); that III’ mining-seepage flow is significantly lower than that of II aquifer with obvious synergistic response of mining-seepage, its total amount of the flow close to the actual mine water in the same period; that the initial section W01 mining face is the main conducting zone, with mining-seepage flow sourced from direct“excretion” of III aquifer and indirect supply of II aquifer; that total amount of other mining areas was stable in low-level, mainly from the seepage of III aquifer mining seepage and a small part from the cross-layer replenishment of II aquifer due to periodic subsidence fractures; that strategy of “Protecting II aquifer by Controlling III” and the flexible recovery mode are adopted in the case of large and thick multi-aquifers, in which safe mining height in the western and eastern areas was increased to about 8−12 m and 16 m, respectively, lead to obvious effect on the aquifers protection confirmed by the significantly decreased abnormal level of seepage in the continuation mining area and the phenomenon of no water inrush.
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