折射波层析成像在探测煤田陷落柱中的应用

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。

Application of Refraction Tomography to Detecting Collapse Column in Coal Mine

The geological anomalies of faults and collapse columns are mostly detected by the methods of reflection wave and channel wave when utilizing seismic exploration in the coal mine roadways.Due to the refraction wave and the three-dimension（3-D）problem,the result of tomography is beyond our expectation.In this paper,the condition of tomography is satisfied by correcting first break.And collapse columns are mainly detected by tomography through the refraction wave.The method and two ameliorating points for tomography in this paper are as follows：First break refraction travel time correction.According to the law of refraction propagation,the delay time of shot points and receiver points are calculated by simulated annealing method.Then,the travel time of the first break refraction can be corrected to the travel time of placing both shot points and receiver points are on the refraction interface.Add the grid density around shot points when Fast Marching Methods（FMM）is used for ray tracing to improve the stability of inversion.The models are smoothed by nine-points moving average technique for improving the results of tomography during the inversion calculating.The methods are applied to seismic data of underground roadway in a coal mine.Comparing with the results of underground Transient Electromagnetic Method（TEM）and surface 3-D seismic method,the result of collapse column being detected by tomography is better.