矿井多波多分量地震方法与试验

Method and test of mine seismic multi-wave and multi-component

多波多分量地震勘探近些年发展迅速,但其在矿井地震中的研究与应用仍不足。矿井全空间效应下波场复杂,在可激发出的体波、煤层槽波、巷道面波与声波等中的有效波与干扰波成分随成像波型选择而改变;同时来自空间多方向的地震波混叠,无方向性的成像难免会出现假象,影响矿井地震勘探的精度。为有效利用不同类型波进行成像,提出基于地震波偏振特性的矿井多波多分量地震方法。此方法利用三分量地震记录,通过时窗自适应的极化分析方法获取准确极化特征参数,避免了因时窗选取不准确而造成极化参数错误的问题;其在散射原理基础上构建的极化滤波函数包含偏振因子和方向因子,可随成像点空间位置及成像的波型的变化而实时更新;偏振因子利用信号的偏振系数可压制非线性干扰波,达到提取纵横波及勒夫型槽波等线性极化波的作用,提高矿井地震信号的信噪比;方向因子根据成像点空间位置与特定波型的振动方向的空间关系,不仅可分离振动方向不同的波(如纵波与横波),还能获取空间任一点的地震波信号,从而实现针对空间任一位置的多波偏移成像。现场试验表明:在岩巷中可分别进行纵波和横波的成像,两者相互验证,提高了探测准确度,同时其探测区域空间位置不受地震测线的约束,可实现测线范围外的地震探测,解决矿井地震勘探施工空间受限的问题;在煤巷中可分别进行槽波与体波的成像,解决槽波反射探测距离受限的难题,故在槽波勘探中建议采用三分量接收,理想情况下,采用煤层三分量和顶板三分量同时接收,形成槽波、体波六分量记录,作为槽波、体波联合勘探的基础数据。

Multi-wave and multi-component seismic exploration has developed rapidly in recent years,while its research and application in mine seismic is still insufficient.The wave field in mine full space is complex as the components of effective wave and interference wave in the excited body wave,coal seam channel wave, tunnel sound wave and surface wave change with the selection of imaging wave type.At the same time, seismic wave aliasing from multiple directions in space inevitably leads to the false appearance of undirected imaging,which affects the accuracy of mine seismic exploration.In order to make full use of different types of waves for imaging,a multi-wave and multi-component seismic method based on the polarization characteristics of seismic waves is proposed in this paper.This method obtains accurate polarization characteristic parameters through time-window adaptive polarization analysis methodavoiding the problem of incorrect polarization parameter caused by inaccurate selection of time window. The polarization filtering function constructed on the basis of the scattering principle includes a polarization factor and a direction factor,which can be updated in real time with the change of spatial position of the imaging point and wave type.The polarization factor can suppress the nonlinear interference wave by using the polarization coefficient of the signal so as to extract the linear polarization wave such as P-S wave and Love channel wave,and improve the signal-to-noise ratio of the mine seismic signal.According to the spatial relationship between the spatial position of the imaging point and the vibration direction of the particular wave type, the direction factor can not only separate the waves with different vibration directions ( such as P-wave and S-wave) ,but also obtain the seismic wave signals at any point in the space.Thereby,multiwave migration imaging for any position in space is realized.The result of field tests shows that the detection accuracy can be improved by carrying out P-wave and S-wave imaging respectively in rock tunnel and the two are mutually verified. Meanwhile, the spatial position of the exploration area is not constrained by the seismic line,which can realize the seismic exploration outside the range of the survey line and solve the problem of limited construction space of mine seismic exploration.By carrying out channel-wave and body-wave imaging respectively in coal roadway, the problem of limited detection distance of channel-wave reflection is solved.Therefore, three-component reception is recommended in channel-wave exploration.Ideally, six-component record of channel-wave and body-wave can be formed by adopting the three-component of the coal seam and the three-component of the roof at the same time,which can the basic data for joint exploration of channel-wave and body-wave.