伪三维电阻率成像技术在煤矿采空区勘探中的应用

Application of Pseudo Three-dimensional Resistivity Tomography Technology in Coal Mine Goaf Exploration

传统的直流电阻率法二维成像方法在复杂地质结构勘探中存在局限性,无法准确恢复三维地下电性结构,同时当测区范围比较大时,真三维直流电阻率勘探要求一次性布极,受硬件、成本等因素限制,基本不具备实施条件。本文以襄樊到荆州铁路沙岗煤矿老窑采空区勘探为例,设计了二维多剖面交叉布线的伪三维勘探方案,使用常规高密度电法设备进行野外数据采集,通过基于八叉树网格剖分的三维电阻率成像算法获得了工区地层和小煤窑采空区的高精度三维电性结构,经与区域地质资料、钻探成果资料对比验证,工区内高电导率异常分布特征可以良好地反映工区地层界线和老窑采空区空间分布特征。上述应用研究表明,基于伪三维采集方式的三维电阻率勘探方法可以有效识别具有连通性特征的地质异常信息和勘探目标,具有良好的成像精度和实用性,对突破二维成像的局限性和三维电阻率勘探的推广应用具有现实意义,在近地表不良地质勘探领域具有广泛的应用前景。

The traditional two-dimensional DC resistivity imaging method has limitations in complex geological structures exploration,which is unable to accurately restore the three-dimensional underground electrical structure.When applied to the relatively largesurvey area,the true three-dimensional DC resistivity exploration requires one-time electrodes layout,which is basically not feasible due to hardware,cost and other factors.In this paper,taking the exploration of the goaf in Shagang coal mine on Xiangfan-Jingzhou railway as an example,a pseudo-3D exploration scheme with two-dimensional multi-section cross wiring is designed,and the conventional multi-electrode electrical equipment is used for field data acquisition.The high-precision 3D electrical structure of the stratum in the work area and the goaf in the small coal mine is obtained by the 3D resistivity imaging algorithm based on octree grid division.Compared with the regional geological data and drilling results,the abnormal distribution characteristics of high conductivity in the work area can well reflect the spatial distribution characteristics of the stratum boundary in the work area and the goaf in the old coal mine.The results application shows that the three-dimensional resistivity exploration method based on pseudo-three-dimensional acquisition method can effectively identify the geological anomaly information and exploration targets with connectivity characteristics,and has good imaging accuracy and practicability,which has practical significance for breaking through the limitations of two-dimensional imaging and popularizing the three-dimensional resistivity exploration,and has broad application prospects in the field of near-surface unfavorable geological exploration.