Equivalent analysis method of electromagnetic waves propagation in arched tunnel

The attenuation characteristics of electromagnetic waves propagation in an arched tunnel cannot be studied by means of the classical theory method. Based on the equivalent analysis method, the lowermost attenuation mode of the arched tunnel was analysed and compared with attenuation modes of the circular tunnel with the equal cross sectional area. The results show that it is feasible to compare the lowermost attenuation mode of the arched tunnel with that of the circular tunnel. The influence of the relative permittivity of tunnel walls is significant. The different equivalent modes are adopted according to different relative permittivity values.