| The Transient Electromagnetic Method (TEM) is a time-domain geophysical methods, its widely used in mineral exploration, disaster prediction and engineering applications in areas such as. In the process of tunnel construction, faults, fissures, caves and other common adverse geological body in the tunnel construction process, it may lead to geological disasters such as mud sudden inrush of water occurs. Because of the transient electromagnetic method sensitive low resistivity body, Water to the surrounding rock its belongs to the relative low resistivity body, References transient electromagnetic method to tunnel geological prediction become a hot topic in recent years. Response characteristics for the poor aqueous tunnel construction and tunnel water inrush transient electromagnetic sudden mud disaster detection and prediction of TEM studies carried out the following three aspects:(1)The geological model of the complex 2D transient electromagnetic forward modeling software using Ansys electromagnetic, Based on the full analysis of the parameters of the model, The numerical simulation of two-dimensional tunnel construction and water bearing structure model and according to the special structure of the electromagnetic response characteristics, at the same time, the whole process of transient electromagnetic detection of view rendering. The main results are as follows:the numerical simulation by numerical simulation results can be seen, the whole space and tunnel space transient electromagnetic response differences are mainly concentrated in the early. Low resistance breaking effects of transient electromagnetic response mainly focus on:(1) crushing with thicker response value is bigger; (2) the broken belt distance face closer response value is bigger; (3) the broken with larger response value is bigger; (4) the relative electrical and the difference of surrounding rock increases, the response value is bigger. The water filled cave different plumpness of transient electromagnetic response is shown as:the greater the degree of karst cave filling, the electromagnetic response is more obvious.(2) According to the similarity principle, the material selection of the appropriate design, the physical model experiment, the low resistance geological body modeling and analysis of the transient electromagnetic response. The main results are as follows:the existence of tunnel space have a certain impact on the detection results, the influence is mainly concentrated in the size of the impact on the detection signal, has little effect on the detection range and detection response value of attenuation and reflect the phenomenon. According to the different position of low resistivity, electromagnetic induction decay curves and the multichannel map showed certain regularity. Effect of metal interference simulation, results show that the metal interference has great influence on the detection results, the general should be as far as possible behind the face to the existence of a large number of metal or metal interference disruptors should stay away from the tunnel face.(3) With the Cenxi tunnel and Hill Foot tunnel for example, combined with the geological survey report and record of actual excavation, tunnel water gushing prediction problem, and introduces the sector detection method, the prediction results and the actual excavation results, prediction results are reliable. |
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