| In recent years, with the deep development of China’s coal exploitation, it present characteristics of multi-source geological-disaster in roadway excavation, water damage, as one of the key factors that has seriously affect the safety production in coal mine. Currently, transient electromagnetic technology have become one of the main means to detect water damage ahead of tunnel in roadway excavation, but as equipment, data acquisition method, data processing and interpretation method and other restrictions, its test results still cannot satisfy the actual needs of production, so studying on roadway advanced detection technology by transient electromagnetic method has important theoretical and practical significance actively.Based on the current research knowledge, paper studies on the advanced water detection technology in roadway construction. Firstly, through the summary and analysis of the regular transient electromagnetic technology theory and interpretation methods, an expression for the step response of small multi-turn square loop is derived, and its accuracy is verified through error analysis. Secondly, through studying on the algorithm for FDTD of Maxwell equations, and improving on settings of transient field source especially, the3D FDTD programs has been developed based on VC++.Net. Combined with geologic conditions in roadway construction, the cubic, plate and column water model ahead of tunnel are selected and simulated respectively to exposit the diffusion regularity and exception response characteristics at central point of loop in full space. Thirdly, through studying on data collection system, data processing and interpretation methods, a set of advanced detecting technology for transient electromagnetic method has been improved and formed. In which, it improves the data measuring accuracy of transient field by optimizing the functions and parameters of instrument host, device shape and damping situation of loops, in particular, it increases the reliability of data collected during the early and middle period of transient field. Combined with the test conditions of roadway, the four-section arrangement for advanced detection is proposed, it enhances the strength of site observation. Considering the existence of turn-off time of current in working of instrument, according to the full analysis on the influence range of turn-off time to exciting field spectrum and transient field, the algorithm for the whole period apparent resistivity in full space is derived. As the intersection characteristics of smoke rings formed by different survey points arranged as sector observing system in front of roadway, the means for spread stack interpretation of apparent resistivity is proposed. Lastly, to discuss the interference of roof bolt that one of interfering factors in driving workface, the range and degree of interference is obtained by testing for tow roof bolt in underground tunnel, to some extent, it provides the basis for field data collection and correction. By constructing an underground sump model, and observing the data of transient field induced by less than100m3water that25m ahead of tunnel dynamically, the response characteristics of transient field for small aquifer is received. The results of theoretical analysis, physical experiment and field application show that, the data collected by the improved transient electromagnetic system for advanced water detection have high quality, and its electrical imaging resolution is good.Through theoretical and practical research, the paper achieve a good many cognition about advanced water detection by transient electromagnetic method in tunnel, the established probing system of transient electromagnetic technology have a strong practicality in actual detection. Because of the more complexity of transient electromagnetic system and limitation of research time, the basic exploration theory, weak signal extraction for aquifer and data correction interfered by field factors are still further studies in the future, so as to provide the solid foundation for improving the effective of water detection, and to ensure the safe production of roadway excavation. Figure [99] Table [12] Reference [112]... |
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