湖南宁乡大成桥充水矿山疏干区岩溶系统水气压力监测及突变特征

Character of water or barometric pressure jump within karst conduit in large strong drainage area of karst water filling mine in Dachengqiao,Ningxiang,Hunan

湖南煤炭坝煤矿是我国著名的大水矿山,开采标高已降至-400m,每小时排水量11 000m^3。长期的疏干排水,已形成面积达219.19km^2的地下水降落漏斗。以往的调查资料表明,矿山疏干诱发的岩溶塌陷主要发生在疏干开始、地下水位下降到基岩面附近、矿坑发生突水突泥灾害等3个阶段,在疏干区应该无诱发因素导致岩溶塌陷的发生。但近年来煤炭坝煤矿疏干区大成桥的岩溶塌陷特征表明,尽管相关部门采取了一系列处置措施,但岩溶塌陷仍然频繁发生。为了进一步揭示该地区岩溶塌陷发育规律,使处置决策更加科学化,作者所在团队选择大成桥为典型区,通过岩溶系统地下水气压力监测,分析诱发岩溶塌陷的动力来源及其变化规律。结果表明,疏干区岩溶管道裂隙系统中水气压力突变现象极为明显,年最大变幅达54.72m,瞬时水气压力变化速率最大为70.6cm/min,造成这一现象的主要原因是气爆、地下洞穴(溶洞、土洞)垮塌。

Meitanba Coal Mine, Hunan Province, is one of the coal mines famous for karst water flooding in China. Its current mining level is about 400 m and the quantity of pumped water from the mine is about 11 000 ma per hour. For long, due to the continuous mine water drainage a great groundwater depression cone with an area of 219.19 km2 has been formed. Generally, most sinkholes induced by the mine drainage mainly occur in three stages, which include drainage beginning, groundwater level dropping beneath the bed rock surface and the occurrence of water inrush incidents, so sinkholes would not be appeared in dewatering zone. But more and more sinkholes have formed in recent years, even though the authorities have taken a se- ries of countermeasures to control these karst hazards. In order to analyze the mechanism of sinkhole forma tion and help the government make decision, the Dachengqiao region was selected as a pilot site to identify the dynamic source of sinkholes. Data derived from the monitoring of water or barometric pressure within karst conduit show that the fluctuation of barometric pressures in the dewatering zone is extremely signifi- cant with a maximum fluctuation range of 54.72 meters happens in a year and a maximum instant variation velocity of 70.6 cm/min, which is believed to the air blasting and soil collapsing triggered by the sinkhole collapses that create the abrupt jumps of the barometric pressure.