Application of reflected in-seam wave detection for small faults in thick coal seams

In general, the fault distance and extension length of small faults in the working face of thick coal seams and extremely thick coal seams are short. Due to the limitation of resolution, it is generally difficult to detect such small faults with current methods and instruments. The unclear detection of small faults will have a great impact on the efficient recovery of the intelligent working face. To solve this problem, the numerical simulation and field experiment of small fault reflected in-seam wave detection in the thick coal seam are carried out. In terms of numerical simulation, the three-component elastic wave simulation of the numerical models with small faults(the drop less than 3 m) in thick coal seams(6 m) and extremely thick coal seams(20 m) is conducted by using the staggered grid finite difference method. On the basis of the spectrum analysis of the numerical simulation results, the characteristics of the direct in-seam wave and the reflected in-seam wave in different models are studied. In terms of practical exploration, through the comprehensive interpretation of transmission and reflection data of the actual developed faults in thick and extremely thick coal seams in different mining areas, the exploration of small faults by transmitted and reflected in-seam wave is studied. The research shows that the detection of small faults in the working face of thick coal seams and extremely thick coal seams by reflected in-seam wave is more recognizable and accurate than that by transmitted in-seam wave.