Study of karst groundwater flow characteristics of a mine in Pingnan county, Guangxi through connection test
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摘要: 广西平南某矿区在人工疏水过程中地下水位持续下降,形成以采区为降落漏斗、周边地下水向采区径流排泄的地下水流场。位于矿区东侧的秦川河成为危及矿区施工安全的最大隐患。为了查明矿区岩溶地下水径流途径、径流特征,进而了解矿区采矿排水的主要来源及周边地表河的影响,在矿区周围进行了地下水连通试验。试验结果表明:矿区岩溶含水介质渗透性差异较大,含水层各向异性明显;矿区北部、东南部存在连通性较好的地下水径流带,北部流速为0.3 ~ 20 m/h,东南部流速为3.72 ~ 98 m/h;矿区南部、西南部与周边地下水连通性较差,与矿区以南的浔江存在地下分水岭;矿区东部一采区矿坑排水主要来自东侧秦川河渗漏补给及北部地下水侧向径流补给,矿区西部二采区矿坑排水补给来源为北部地下水侧向径流及大气降水。因此,采矿疏水过程中应及时掌握秦川河水位变化情况,采取帷幕等有效手段对水害进行治理,以确保生产安全。Abstract: The mine in Pingnan county, Guangxi is located in a closed hydrogeological basin which borders the Qinchuan River in the east, the Xunjiang River in the south, the Wujiang River in the west and the watershed of groundwater in the north. The strata exposed in the mine area are mainly Devonian limestone and calcite dolomite, and Quaternary Holocene loose deposits. Declining groundwater levels due to artificial drainage lead to a redistribution of the groundwater flow field and the mining area became a cone of depression in the aquifer. The Qinchuan River is a potential risk to mining safety. In order to understand the flow path and percolation velocity of groundwater, and recharge sources of drainage water in the mine area, a connection test was conducted. The results of the connection test indicated that the medium of aquifer was highly heterogeneous and anisotropic because there was a huge difference in permeability between test sections. Moreover, the northern and eastern connectivity was better than that of the southern one. Groundwater velocity ranged from 0.3 to 20 m/h in the north and ranged from 3.72 to 98 m/h in the east. There is a groundwater watershed between the mine area and Xunjiang River, so the hydraulic connection of mine in the south and the periphery was weak. Therefore, the lateral runoff in the north and the leakage from the Qinchuan River were mainly recharge sources of groundwater in the first mining area based on the connection test results. In addition, except the lateral runoff in the north, local precipitation was the main recharge source for groundwater in the second mining area. Finally, in order to choose an appropriate time to drain groundwater, fluctuations in the level of Qinchuan River should be recorded and analyzed from a security perspective. On the other hand, some engineering measures should be considered to block groundwater flow, such as curtain grouting anti-seepage.
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Key words:
- karst /
- groundwater /
- connection test /
- Pingnan, Guangxi /
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