Effects of cross section of mine tunnel on the propagation characteristics of UHF radio wave

The paper studies the propagation characteristics of UHF radio wave in circular tunnels, rectangular tunnels, arched tunnels, ellipse tunnels, trapezium tunnels and semi-circle tunnels. A conclusion is made that trapezium tunnels and semi-circle tunnels can equivalent with circular tunnels with the same area of cross sections; these tunnels have a same formulation of attenuation rate though their cross section is different. The larger the area of cross sections is, the lower attenuation rate is, and the shape of cross sections affects on attenuation rate too. When the diameter or the larger side is larger than about fifteen times the free-space wavelength, attenuation rate is very low and hardly related to the shape of cross sections, and doesn´t severely depend on area of cross sections of tunnel any more, and the wave can be looked upon transmitting at free space.