充水矿山疏干区岩溶系统水气压力突变及其诱发岩溶地面塌陷的机理研究

The mineral deposit filled with karst water in a kind form of space naturally appears the relative hydrogeological peculiarity; thus the special hydrogeological and engineering geological problems happened in mining times. Recently, there are a series of gigantic sinkhole hazard associated with dewatering of aquifers in mineral deposits filled with karst water, and gave great influence to citizen life.The further study of the mechanism of karst collapse formation was affected by external factors are in accident. In the dewatered desiccation area, drainage factor always exist so that karst collapse hazard are in active periods. It is very important to take a detail research about mechanism of karst collapse formation through increased pressure of water or gas in the karst system. Especially cavitation erosion lab tests would be necessary. The project steps are sketched as following. Firstly, the applicant selected sinkhole areas of Hunan and Anhui as the typical research sites and to take investigation and detection of geological background and dynamic condition. Through systematic analysis of sinkhole development with the action of dewatering and rainfall, build the geological mode of sinkhole formation. And then, high resolution piezometers with dataloggers introduced to monitor pressure of water or gas within karst conduit in situ. Combine cavitation erosion model experiment，monitoring data and numerical simulation, to research the mechanism of sinkhole formation and its development rule. Finally, its influence factors will be study to establish the approaches and methods for monitoring and prevention of sinkhole.

近年来，岩溶充水矿床在开采中形成了大范围的疏干区，在疏干区频繁出现一系列大型、特大型岩溶塌陷灾害，经济损失巨大并给当地老百姓造成了恐慌。许多岩溶塌陷事件由于外在影响因素存在偶发性，严重影响了岩溶塌陷机理的深入研究，而在岩溶矿山疏干区，疏干排水影响因素一直存在，岩溶塌陷仍处于活跃期，易于捕捉到影响岩溶塌陷的关键因子。因此本项目选择湖南宁乡煤炭坝矿区、安徽铜陵狮子山矿区分别代表煤矿、金属矿典型矿山作为研究对象，以现场监测岩溶地下管道裂隙系统中水气压力突变为突破点，深入揭示矿区岩溶系统中水气压力突变的原因及诱发岩溶塌陷的机理。首先根据岩溶塌陷发育的基础地质条件和研究岩溶塌陷的发育分布规律，建立岩溶塌陷发育的地质模式；然后通过室内气蚀物理模拟试验、野外监测站监测数据，确定矿区岩溶管道裂隙系统中水气压力突变的主要影响因素，研究防治措施，为矿区的岩溶塌陷处置提供科学依据。

近年来，岩溶充水矿床在开采中形成了大范围的疏干区，并在疏干区频繁出现一系列大型、特大型岩溶塌陷灾害，经济损失巨大并给当地老百姓造成了恐慌。许多岩溶塌陷事件由于外在影响因素存在偶发性，严重影响了岩溶塌陷机理的深入研究，而在岩溶矿山疏干区，疏干排水影响因素一直存在，岩溶塌陷仍处于活跃期，易于捕捉到影响岩溶塌陷的关键因子。因此本项目选择湖南宁乡煤炭坝矿区、安徽铜陵狮子山矿区分别代表煤矿、金属矿典型矿山作为研究对象，以现场监测岩溶地下管道裂隙系统中水气压力突变为突破点，深入揭示疏干区岩溶系统中水气压力突变的原因：一是雨季土层密封性增强，地表水的补给使岩溶地下水位上升造成岩溶空腔中气体的压缩；二是地下岩溶管道系统中的管道规模形态的变化导致地下水流速的变化，形成高压气团；三是土洞形成过程中的水击效应；明晰了疏干岩溶区岩溶塌陷的主要形成过程：降雨→第四系饱水，形成密封层→岩溶地下水位上升→气爆→土体剥落→水击效应→土洞形成→地面塌陷。由此，通过室内岩溶气爆-水击模型实验，进一步揭示了气爆的精细过程：密闭系统岩溶水位的下降，导致空腔内的水气压力处于负压状态，且进行高频率的振动，这是以前地下水位监测从未发现的。说明岩溶空腔顶部的岩土体不仅仅受到负压的吸蚀作用，并且会受到水气压力的高频振动所形成的共振效应影响。根据上述研究结果，研究了岩溶空腔水气压力平衡方法（岩溶塌陷防治措施之一）的有效性。当通气孔的直径大于岩溶管道直径的10%时，可消除岩溶空腔水气压力突变，这一发现将为岩溶矿山疏干区岩溶塌陷灾害的有效防治提供了理论依据。此外，提出的岩溶水气压力监测技术也将替代传统的水位测量方法，逐步推进岩溶塌陷监测、预警预报的发展。