The direct and accurate estimations of coal thicknesses are prerequisites for intelligent mining practices. One of the most effective methods for detecting the distributions of coal thicknesses in coal mining panels is the in-seam seismic (ISS) method. In the present study, after examining the formation processes and propagation characteristics of refracted P-waves in ISS data, it was concluded that the refracted P-waves in coal seams are mainly formed by the multiple transmission and reflection of the P-waves between the coal and rock interfaces of roof and floor at critical angles. This results in the refracted P-waves having strong periodicity, and these periods are proportional to the coal thicknesses. This study adopted numerical simulation models with different coal thicknesses, and the aforementioned periodicity characteristics were examined. It was found that the coal seam thicknesses could be calculated using the periods of the refracted P-waves. However, in thin- or medium-thick coal seams, it was found that multiple transmitted P-waves overlapped and the periods could not be read directly. Therefore, in order to solve this problem, this study composed source wavelets with the main frequency of the source signals and then composite synthetic P-waves by convoluting the source wavelets with the sequences of various coal thicknesses. The suitable estimated coal thickness corresponded to the minimum value of the errors between the synthetic and actual refracted P-waves. An experiment was conducted in the No. 42224 panel of the Chaigou Coal Mine in order to validate the proposed method. The experimental results revealed that the estimated coal thicknesses from the refracted P-waves were consistent with the actual geologic conditions in the coal mine. Due to the fact that the refracted P-waves arrive earlier than other waves in seismic records, the refracted P-waves could be easily identified and processed. Overall, the proposed method was found to be a simple application process for accurate coal thickness estimations.

直接和准确估算煤层厚度是智能采矿实践的前提。探测煤层中煤厚分布的最有效方法之一是煤层内地震（ISS）方法。在本研究中，通过研究ISS数据中折射P波的形成过程和传播特性，得出结论，煤层中折射P波主要是由煤层之间P波的多次透射和反射形成的。屋顶和地板的煤和岩石界面处于临界角。这导致折射的P波具有很强的周期性，并且这些周期与煤的厚度成正比。本研究采用了不同煤厚的数值模拟模型，并检查了上述周期性特征。已经发现，煤层厚度可以利用折射的P波的周期来计算。但是，在薄或中厚的煤层中，发现多个传输的P波重叠，并且不能直接读取周期。因此，为了解决这个问题，本研究将源子波与源信号的主频率组合在一起，然后通过将源子波与各种煤厚度的序列卷积在一起，合成合成P波。合适的估计煤层厚度对应于合成和实际折射P波之间的误差最小值。为了验证所提出的方法，在柴沟煤矿的42224号面板中进行了一项实验。实验结果表明，通过折射的P波估计的煤厚度与煤矿的实际地质条件是一致的。由于折射的P波比地震记录中的其他波更早到达，因此可以轻松地识别和处理折射的P波。总体而言，发现该方法是准确估算煤层厚度的简单应用过程。