• 标题：An Emerging Method Using Electromagnetic Wave Computed Tomography for the Detection of Karst Caves
• 关键词：Electromagnetic wave CT ,Karst caves ,Numerical model ,Absorption coefficient
• 作者：Shenggen Huang ,Jie Lin ,Qikun Huang ,Rongzhu Liang

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Electromagnetic wave CT technology, serving as an emerging geophysical method, is an effective way in detecting underground karst caves. In this paper, a numerical model for electromagnetic wave CT detection was established using Finite Difference Time Domain algorithm to interpret the propagation mechanism of electromagnetic wave in karst cave detection. The saturated sands with high porosity are adopted as the fifilling medium of the cave while the limestone is selected as the surrounding rock in this simulation. Propagation rules obtained from numerical simulation are drawn as follows: (1) when electromagnetic wave propagates inside the karst cave, refraction, reflflection, diffraction, and obstacle gain behavior will occur. (2) The refraction phenomenon has relatively more inflfluence on the energy absorption of electromagnetic wave while the disturbance of the waveform is principally attributed to the reflflection phenomenon. (3) The inflfluence of the factors such as the type of fifilling material and water content should be taken into account if the absorption coeffificient of karst caves to electromagnetic wave is inconsistent. Furthermore, the tomographic images  gained from experiment are interpreted according to the simulation conclusions. It is found that the analysis of tomographic images show general agreement with the previous exploration results, so it is feasible to use electromagnetic wave CT technology in karst cave exploration. The research presented herein aimed to serve as a based theory for analyzing tomography results in the fifield of karst caves exploration.