煤巷小构造Rayleigh型槽波超前探测数值模拟

The method of small structure prediction ahead with Rayleigh channel wave in coal roadway and seismic wave field numerical simulation

对煤巷小构造地震波场进行了数值模拟研究,分析了层状煤层中地震波的传播特征.研究表明:(1)在煤巷迎头前方煤层内以纵波震源激发的Rayleigh型槽波相对于体波能量较强,波列较长,波速较低.(2)沿煤层传播的Rayleigh型槽波在小构造面上产生Rayleigh型槽波反射波,反射Rayleigh型槽波垂直分量相对于水平分量能量较强.沿煤层反向传播的反射Rayleigh型槽波在煤巷迎头面上转换为沿煤巷底板传播的Rayleigh面波.沿煤巷底板可以接收到能量较强的反射Rayleigh型槽波产生的Rayleigh面波,其可以作为超前探测小构造面的特征波.在地震记录上反射Rayleigh型槽波产生的Rayleigh面波波至最迟,在时间域与其他波列时间间隔较大,其垂直分量能量相对于水平分量较强,在地震记录上容易识别.(3)在相同的地质条件下应用反射地震超前探测方法,标志煤巷迎头前方存在小构造面的反射地震波能量较弱,受煤巷顶、底板界面和采煤迎头面的强反射波干扰,在地震记录中难以识别.

The seismic wave field in layered coal seam is simulated with coal road model. Propagation characteristics of seismic wave in horizontally stratified coal seam are analyzed. The results showed： （1） the P-wave source in the coal bed floor before coal heading face can excite Rayleigh channel wave in coal seam. The energy of Rayleigh channel wave is stronger than body waves. The wave train of Rayleigh channel wave is longer than body waves. And wave velocity is lower than body waves. （2） The Rayleigh channel wave generates reflected Rayleigh channelwave on the small structure before coal heading face. The energy of vertical component of Rayleigh channel wave is stronger than horizontal component energy. The reflected Rayleigh channel wave is converted into Rayleigh surface wave at the head of the coal roadway. Rayleigh surface wave can be recorded along the floor of tunnel. The Rayleigh surface wave is recorded last in time domain. The time interval between Rayleigh surface wave arrival time and others＇ is longer. And it is easily recognized and extracted in seismic records. The energy of vertical component of the Rayleigh surface wave is higher than horizontal component. （3） In same conditions, the method of reflected-wave seismic prediction ahead is not applicable for detecting small structure before coal heading face. The energy of reflection waves from the interfaces of small structure before coal heading face is very low. Under the influence of high-amplitude reflection waves excited on the interfaces of roof, floor and coal heading face in coal tunnel, it is difficult to recognize and extract the reflected-wave of small structure before coal heading face in seismic records.