On the Possibility of Describing Field Variations in Curved Tunnels by Using Modal Approach to the Propagation in Straight Tunnels

When the tunnel wall is curved, the existing electromagnetic field prediction methods will encounter serious difficulties in solving the problem, such as the difficulty in obtaining closed-form expressions, and the obvious increase in computational complexity and computational burden. A simplified method is presented in this paper. And the possibility of the field prediction for bending roadways by modal approach in straight roadways is discussed. Firstly, the propagation law in a curved roadway is analyzed. On this basis, the geometrical structure of the curved roadway is simplified. It is equivalent to a splicing of several straight roadways with different inclination angles. Then the channel model is accomplished by using the modal method for the propagation in the straight roadway. Compared with other approaches, the feasibility of the proposed method is verified.