【作者】 杨真；

【导师】 林在康； Maochen Ge；

【作者基本信息】 中国矿业大学 ， 采矿工程， 2009， 博士

【摘要】 在煤矿生产中,很多透水事故都是由于地质资料的缺失或不精确而意外打通废旧矿井、含水空硐造成的。据统计,近年来国内60%以上的淹井事故是由于老空区突水引起的。因此,需要一种行之有效的探测空硐和煤柱未知边界的方法以解决此类问题。在以往的研究中,由于对槽波形成的机理认识不足、在槽波数据处理的理论与方法上不够成熟,且采用基于ISS(In-seam Seismic)反射界面的探测技术,拘泥于传统的地震地质勘探方法,所以造成槽波探测技术在90年代后一直处于停滞状态。为了解决煤层空硐探测技术难题,美国MSHA资助8个机构进行各种空硐探测方法的可行性研究,其中包括宾夕法尼亚州立大学采用的煤层间槽波微震法ISS。作者参加了课题组在Black King Mine和Cumberland Mine两个煤矿的研究,结果显示采用寻找可识别埃里震相的保守方法在定位煤层空硐反射边界时,其探测范围和精度上均优于采用其它技术所获得的效果。据研究可知,煤层越薄,槽波频散特征越强,而槽波的速度很大程度上依赖于频率,因此很难精确确定槽波速度。并且煤层越薄,槽波的频率越高,阻抗越大,槽波在介质中传播的距离越短,探测的范围越小,识别反射波的难度越大。这些给利用槽波定位薄煤层的空硐边界造成了很大难度。本论文以Black King Mine煤矿厚度为0.9m薄煤层条件下所作的研究为工程背景,系统分析了薄煤层槽波的频散特征,并在理论上解释了薄煤层槽波高频域和低频域形成的主要原因。在推导出薄煤层槽波相速度和群速度关系方程的基础上,采用数值分析法求得薄煤层槽波在基阶模式、第一高阶模式和第二高阶模式下的频散曲线。在厚度为0.9m的薄煤层中使用放炮法做微震震源,通过分析所记录的薄煤层槽波信号发现,薄煤层槽波在频域中存在着高频和低频两个独立且不连续的波段。通过小波分析,可以看到这两个频域几乎在同一时刻触发,并且其小波相关系数的分布在同一时域中表现出一定的相似性。这些是薄煤层槽波不同于厚煤层槽波的显著特点。由于震源布置于煤层中心,炸药的能量对顶板的扰动对第二高阶对称波形模式下槽波高频部分的形成起着关键作用,因此,在这一对称高阶波形模式下的槽波的波速基本上和煤层顶底板S波的波速一致,对实验点确定顶低板岩层中S波的波速起着重要的作用。论文详细介绍了采用基于ISS的薄煤层空硐探测方法,对薄煤层空硐的探测范围和精度进行了研究,达到了预期的效果。论文还验证了采用保守的可识别埃里震相方法的有效性,提出并验证了槽波第二高阶对称波形模式存在的理论。建议采用小波分析法提高实验的精度,在工程实际应用中可以考虑通过对比槽波在未知边界煤柱与已知边界煤柱中反射槽波的时频图,来提高评估未知边界的范围的精度。论文作为基于ISS的煤层空硐探测方法的一部分,与厚煤层、中厚煤层空硐探测方法结合在一起,将组成较为完整的煤层空硐探测方法,计划今后将尽快纳入到数字矿井系统中,在工程实际推广应用中不断完善。更多还原

【Abstract】 Many coal mine inundations would happen when pillars protecting water were broken through to active mine due to absence of necessary geological data or using inaccurate map. According to statistic, 60% of mine inundations were caused by water inrush from goafs. Thus, it is necessary to develop an effective method that can detect void or uncertain boundary of pillar between two adjacent coal or active sites and goafs. In preceding researches, because mechanics of channel waves have not been developed fully and methods of processing channel wave have been limited to traditional seismic geological exploration to indentify reflecting interfaces, the in-seam seismic (ISS) technology has been jammed since 1990s.In order to solve the problem of void detection in a coal seam, the Mine Safety and Health Administration (MSHA) has funded 8 organizations to study the feasibility of void detection using all kinds of methods, including Pennsylvania State University. The research team of Pennsylvania State University is going to use the in-seam seismic method to detect voids in a coal seam. Author has attended two researches in Black King Mine and Cumberland Mine as a member of research team. When the distinguishable Airy phase method was used, the result of research showed that the detecting range and accuracy are better than ones of other technologies using in void detection.According to the result of research, the effectiveness of dispersion is stronger when the coal seam becomes thinner. The velocity of channel wave depends on the frequency, so it is difficult to get exact speed of channel wave in a thin coal seam. In addition, the range of propagation of channel wave decreases because of high frequency. As a result, it will be difficult to indentify the reflected signal from the reflection survey in a thin coal seam.The dissertation focused on the feasibility of void detection in a 0.9m-thin coal seam of Black King Mine, analyzed systematically the dispersion characteristics of channel wave in a thin coal seam, and explained the reason of high and low frequency domain in theory. Based on the deduced equation of phase velocity and group velocity, the dispersion curves of fundemental order, first higher order and second higher order were plotted using numerical method.According to study the seismic signal recorded in the 0.9m-thin coal seam in the condition of dynamite as seismic sources, two frequency bands are shown in energy spectrum. After using wavelet transform, the two frequency bands almost started on the same moment. Furthermore, the wavelet coefficients distribution shows a certain similar behavior in a thin coal, which is outstanding feature that is different from channel waves recorded in a 2.1m-thin coal seamBecause the seismic source set in the middle of coal seam, the vibration of roof and floor caused by dynamite has played an important role to form a second higher order of symmetrical wave shape. The velocity of channel wave in second higher mode is the same as the one of S wave in roof and floor, which is important to confirm the velocity of S wave in rock.The dissertation has detailed the method of void detection using ISS in a thin coal seam, and the results are positive. The research has verified the effectiveness of the distinguishable Airy method, and proved the theory of existence of second higher mode in channel wave. Because channel waves in a coal seam have a distinctive characteristic of dispersion and a wide frequency domain, uncertain boundary of pillar or reflecting interface could be decided using the method of analogy in practical engineering case.The dissertation is part of void detection using ISS technology. If combing with the result studied in a thick coal seam, it will be formed to a systematical method. Author will integrate this technology to the Digital Mine System in future, and this technology will be developed quickly in practical engineering case.更多还原