Water-bearing geological structure is a serious threat to coalmine safety. This research focuses on detecting water-bearing geological structure by transient electromagnetic method. First, we introduce the principle of mining transient electromagnetic method, and then explain the technique of Finite Different Time Domain using in the transient electromagnetic method. Based on Maxwell equations, we derive the difference equations of electromagnetic field and study the responses of water-bearing geological structure using FDTD. Moreover, we establish the relationship between receiving electromagnetic field and geological information. The typical coal geological model of goaf-water is chosen to do the numerical simulation. Besides, we verify the availability of the method by numerical simulation using coal geological model. Finally, we use the method in the coalmine which is located in Linfen city in Shanxi province in China, and the detecting result is verified by drilling.

Due to severe harms of goaf collapse, the goaf exploration and governance has become an urgent issue for protecting the normal life of local people. According to the coal mine geology, different geo-electrical models have been employed for the purpose of discovering the goafs. However, most existing methods require a large amount of computation consumption. In order to address this issue, a forward numerical simulation using the borehole electromagnetic method has been developed in this work to explore the coal mining goafs. The innovation of this method is that the computation consuming can be saved significantly. Numerical simulation demonstrates high effectiveness of the borehole electromagnetic method in coal mining goaf exploration. Therefore, this research provides a new idea for exploring the coal mine goafs by geophysical method.

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