| Construction tunnels often encounter geological disasters such as water inrush and mud out,landslides,and roof crests when passing through areas with poor geological development A large number of production practice cases in history show that the occurrence of geological disasters in construction tunnels will seriously threaten the safety of construction equipment and personnel,delay the progress of construction,and cause huge losses to the project construction.Therefore,the advance geological forecast(referred to as advance forecast)for water and mud inrush during tunnel construction has become an important issue to ensure the safe,efficient and green progress of tunnel constructionTransient electromagnetic method,as a geophysical prospecting method,has been widely used in advance forecasting of tunnels and underground caves during construction.Since the transient electromagnetic method is sensitive to the response of well-conducted geological bodies hidden in the surrounding rocks,it has been successfully applied in the exploration of water-containing disaster structures in front of and near the palm face.The application of traditional transient electromagnetic methods is restricted by various factors.For example,in the TBM construction tunnel,the traditional transient electromagnetic device form is limited by the TBM machinery.The metal components of the TBM itself generate strong electromagnetic interference on the collection of the secondary field attenuation voltage,which makes this type of method currently difficult to apply.TBM construction tunnel.In order to achieve the goal of predicting the tunnel construction in TBM machine and overcome the difficulties encountered in the construction of TBM tunnel by the transient electromagnetic method,this paper proposes a construction tunnel based on electrical source excitation based on previous work Transient electromagnetic advance detection device.Aiming at the different working conditions of the drilling and blasting method and the TBM construction tunnel,the three-dimensional finite-difference time-domain method is used to simulate the distribution law and response characteristics of the transient electromagnetic field in front of the tunnel under the excitation of a single electrical source.An array-type device is further proposed above,which makes up for the lack of detection capability of the electrical source device.By analyzing the distribution and response characteristics of the transient electromagnetic field,this paper considers that the transient electromagnetic detection method based on the electrical source emission device can be used not only in the drilling and blasting construction tunnel,but also in the TBM construction tunnel.The ability of the tunnel to forecast ahead.In order to receive the maximum abnormal response on the tunnel palm face,after a lot of exploration and attempts,this paper proposes an array receiving method based on electric field component acquisition According to the above-mentioned transmitting and receiving methods,a large number of forward modeling of fine faulty geological structures such as aquifers and aquifers in front of the tunnel palm are made using the forward-difference time-domain finite difference method The simulation calculation and analysis of the transient electromagnetic response law of anomalous bodies with faults of different occurrences and distances,and also verified whether the electrical source detection method described in this paper has the potential for fine detection. |
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