钻孔瞬变电磁拟地震反演方法在露天煤矿采空区精细探测中的应用

露天开采煤矿地下存在大量小煤窑采空区,严重威胁煤矿生产安全和人员生命安全。受露天煤矿地表工作环境影响,常规物探手段探测采空区精度较差,而钻孔瞬变电磁探测是一种精度较高的探测方法,属于一种动源动接收的工作方法。为提高资料处理精度,应用滑动时窗波场反变换算法对数据进行高精度波场转换,采用共轭梯度法研究了针对瞬变电磁虚拟波场数据的拟声波介质全波形反演算法,实现了钻孔瞬变电磁数据的拟地震反演,计算了三维数值模型数据的反演结果,并对钻孔径向的小规模低阻异常体取得了良好的成像效果。结合山西朔州地区某露天煤矿的工程实践,对该方法精细探测积水采空巷道形态、性质和规模的实用性和有效性进行了检验。结果表明:钻孔瞬变电磁探测方法是矿井物探与钻探的有机结合与相互补充,拟地震反演方法能够有效应用于露天煤矿采空区的精细解释。

Application of Borehole Transient Electromagnetic Pseudo-seismic Inversion Method in Goaf Fine Detection of Open-pit Coal Mine

There are numerous small colliery goafs under open-pit coal mine, which put great threats to safety of coal mine production and life. Affected by the surface environment of open-pit coal mine, conventional geophysical methods have poor accuracy in detecting goafs. Borehole transient electromagnetic method is a high-precision detection method, which belongs to a dynamic source and dynamic reception operating procedure. In order to improve data processing accuracy, the wavefield inverse transformation algorithm of sliding time window was adopted to preforming data high precision wavefield conversion. The conjugate gradient method was used to study the quasi-acoustic medium full waveform inversion algorithm for transient electromagnetic virtual wavefield data, and the borehole transient electromagnetic data pseudo-seismic inversion was realized. The inversion results of three-dimensional numerical model data show that the favorable imaging effect for the small-scale anomalous body on the radial direction of the borehole can be acquired. In order to test the practicability and availability of the operating method in detecting shape, characteristics and scale of water-logged goaf roadway, the engineering practice of an open-pit coal mine in Shuozhou area of Shanxi was conducted. The results show that the borehole transient electromagnetic detection method is a great combination and complementary of mine geophysical exploration technology and drilling technology. The pseudo-seismic inversion method is an effective application in goaf fine detection data interpretation of open-pit coal mine.