Application Of GPR In The Detection Of Upper Protective Layer In Coal Mining Face

Intelligent fully-mechanized face of coal mine required shearer adjust the height of cutting drum automatically according to the mining environment when the shearer works, and the height of cutting drum automatically adjust based on the thickness detection of the protection layer and coal-rock interface recognition, so protection layer detection of the fully-mechanized mining face has important significance to the intelligent mechanized mining.This paper analyzed the characteristics of the mainstream coal-rock interface detection technology, and summarizes ground penetrating radar(GPR) is the best suitable for the coal-rock interface identification to the mining mode of reserved protective coal seam. In order to provide the basis for the choice of the central frequency and the calculation of the phase velocity and the path loss of the GPR in the coal seam, the relationship between phase velocity, attenuation coefficient and frequency of electromagnetic wave is analyzed based on the loss characteristics of the GPR signal in coal seam. The thickness calculation method of the upper protect coal seam and the identification algorithm of the rock layer were obtained by the path loss and the reflection phenomenon on different medium interface when the electromagnetic wave is used to detect the up protect coal seam, the validity of the method confirmed from the simulation results.In order to improve the interpretation accuracy of the GPR reflection echo data from the coal face detection, using the finite difference time domain(FDTD) method for the forward modeling. Taking the FDTD simulation about point signal source transmission of TE form as an example, analyzed the effect of the perfectly matched layer(PML) absorbing boundary condition to lay the foundation for the finite difference time domain method. The thickness detection, simple geological structure detection, abnormal water and cavity detection, fold coal seam detection, problems of fracture zone and water rich fracture zone detection in coal seam is simulated by FDTD algorithm and the characteristics are summarized. The simulation results provide a basis for the research of the identification of the actual target and the imaging data recognition of the GPR in coal seam.