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在煤矿巷道内进行的地震勘探,主要利用反射波和槽波信息确定采区的断层、陷落柱等地质异常。也可用穿过煤层的初至波来进行层析成像,但效果较差,主要原因是其中包含折射波,并且是三维问题,不易进行层析成像。本文对初至波进行适当的校正,以满足层析成像的条件,探测陷落柱位置。在本文的研究中主要用到的方法和对层析成像的改进包括:初至折射波校正。根据折射波传播规律,用模拟退火法求得炮点延迟时和检波点延迟时,从而将初至折射波旅行时校正为炮点和检波点位于折射界面上的初至旅行时。在用快速推进法(Fast Marching Methods,FMM)进行射线追踪时进行了炮点网格加密处理,提高了反演的精度。在层析成像迭代过程中对模型进行了九点平滑处理,改善了层析成像的效果。本文研究的方法应用于某煤矿工作面井下巷道的地震勘探数据,层析成像结果显示能较好地确定工区内陷落柱的分布范围。
Seismic exploration in coal mine tunnels mainly uses the reflected wave and slot wave information to determine the geological anomalies such as faults and collapsing columns in the mining area. It is also possible to perform tomosynthesis with first arrival waves that pass through the coal seam, but the effect is poor, mainly due to the inclusion of refracted waves and the three-dimensional problem that makes tomography difficult to perform. In this paper, the first break wave is properly corrected to meet the conditions of tomography and detect the position of the collapse column. The main methods used in this study and improvements to tomography include initial refracted wave correction. According to the law of propagation of refracted waves, the simulated annealing method is used to obtain the delay of the shot and the delay of the detective point, so that when the first arrival refracted wave travels, it is corrected to be the first arrival when the shot point and the detective point are located on the refraction interface. In the process of ray tracing with Fast Marching Methods (FMM), the shot grid was encrypted and the accuracy of inversion was improved. During the tomographic iteration, the model is smoothed by nine points to improve the effect of tomography. The method studied in this paper is applied to the seismic exploration data of mine roadway in a coal mine. The tomographic results show that the distribution range of the collapse column in the work area can be well determined.