Study on hydrochemical characteristics and water inflow sources of typical karst water-filled mining areas under the influence of extended mining
Mineral resources are an important pillar of China's vigorous economic development. With the rapid increase in the demand for metal minerals,the original metal mining areas continue to be mined. However,the specific geological conditions indicate that a significant number of ore bodies in China are closely associated with the limestone strata. As a result,the karst aquifer has emerged as one of the major hidden dangers threatening the deep mining of these ore deposits. Therefore,it is an important topic to study the prevention and control of pit water in mines of karst areas,but there is a lack of comprehensive case studies that have revealed the changes in water sources in pits due to deep mining on the basis of hydrochemical data from water inflow points at different mining levels. The Makeng mining area is a typical karst water-filled mining area in East China. Its hydrogeological conditions and pit water-filling conditions are complex,presenting significant challenges for water prevention and control efforts. In this study,59 sets of hydrochemical data were selected from the water inflow points of horizontal tunnels at four mining levels (+420 m,+300 m,+200 m and+100 m) in the Makeng mining area from 2006 to 2016. Combined with the evolution law of the groundwater flow system in the mining area,various hydrochemical methods such as Piper three-line diagram,ion ratio,Gibbs diagram and chlor-alkali index were used to analyze the source of water inflow. The mixing ratios of different water sources were calculated,and a conceptual model of evolution of water sources at the water inflow points was generalized. Besides,the hydrochemical causes and recharge sources of water inflow points at different mining levels in the mining area were discussed.The results show that the decrease of groundwater levels gradually slowed down while and water inflow continuously increased during the mining process;therefore the recharge sources of pit water inflow points constantly changed. Secondly,the long-term water drainage and depressurization changed the direction of groundwater runoff in the mining area. Additionally,the water temperature,pH and TDS increased with the increase of mining depth,and the hydrochemical type gradually changed from HCO3-Ca type to HCO3·SO4-Ca type and HCO3-Na·Ca type. The dissolution of carbonate salt is the main controlling factor for the formation of groundwater in the mining area. Besides,controlled by faults and other geological structures,some water inflow points were influenced by different water sources in some degree. Moreover,different mining levels were also affected by pyrite oxidation,cation exchange,mixing action,etc. The sources of water inflow points at+420 m and+300 m were from karst water and P1j1 sandstone water,while the main sources at mining levels of+200 m and+100 m were also from karst water. The water inflow point at+100 m was recharged by low-temperature hot water along the water diversion fault from deep granite. The Ca2+and Cl-equilibrium models were used to calculate the respective ratios of mixing karst water with sandstone fracture water and of mixing karst water with hot water from deep granite. The recharge rates of fracture water at+420 m and+300 m were about 22.7％-82.8％,and the recharge rates of low-temperature hot water from deep granite at+100 m were 35.1％-38.3％. In the future,the monitoring of water quality in water inflow points at+100 m or above should be strengthened. If necessary,F1 and other faults exposed underground should be grouted so as to prevent the low-temperature hot water from the contact zone between the deep granite and the quartz sandstone of Lindi formation (C1l) from entering the pit along the water diversion structure to recharge karst water. In this paper,the hydrochemical formation of water inflow source in Makeng mining area under the influence of extended mining has been discussed,and the dynamic characteristics of water inflow sources have been preliminarily analyzed,which can provide a certain reference for groundwater management and prevention and control of pit water in the same type of karst water-filled mining area.
万方数据
维普
