Meikuang Anquan (Aug 2024)
Research on three-dimensional forward modeling of underground radio wave perspective and electromagnetic wave propagation characteristics
Abstract
The theory of electromagnetic wave propagation in strata is the basis for underground radio wave detection. There are differences in the propagation of electromagnetic waves in the strata when the detection frequency and coal seam occurrence change. To study the response characteristics of electromagnetic wave propagation under the change of detection frequency and coal seam occurrence. A three-dimensional forward modeling of radio wave perspective was established, and three-dimensional simulation experiments were carried out on different detection frequencies, different coal seam thickness conditions, and different coal rock conductivity ratios. The experimental results show that the attenuation of electromagnetic waves in the coal seam presents two stages, when the transmission and reception distance is small, the attenuation effect caused by geometric diffusion is large, the field strength decreases rapidly, and the attenuation effect of geometric diffusion decreases when the transmitting-receiving distance is large, and the attenuation speed decreases and tends to be stable. When different frequencies are used for detection, the initial field strength value increases, the absorption coefficient of electromagnetic waves increases, and the absorption coefficient changes from 12.28% to 26.67% due to different detection frequencies, and the effective detection distance of radio waves is shortened. The increase of coal seam thickness, the decrease of electromagnetic wave absorption coefficient and the change of electromagnetic wave absorption coefficient per meter of coal seam thickness varies from 2.25% to 17.29%. When the ratio of rock to coal conductivity increases, the radio wave absorption coefficient decreases and the effective radio wave exploration distance increases.
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