Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fo...Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fourier transform related to the electromagnetic response in the frequency and time domains becomes a sine or cosine transform under the excitation of downward-step current.We established a transformation matrix based on the digital fi ltering calculation for the sine transform,and then the frequency domain projection of the TEM data was determined from the linear transformation system using the smoothing constrained least squares inversion method,in which only the imaginary part was used to maintain the TEM data transformation equivalence in the bidirectional projection.Thus,the time-domain TEM inversion problem was indirectly and effectively solved in the frequency domain.In the 3D inversion of the transformed frequency-domain data,the limited-memory Broyden–Fletcher–Goldfarb–Shannoquasi–Newton(L-BFGS)method was used and modifi ed with a restart strategy to adjust the regularization parameter when the algorithm tended to a local minimum.Synthetic data tests showed that our domain transformation method can stably project the TEM data into the frequency domain with very high accuracy;furthe rmore,the 3D inversion of the transformed frequency-domain data is stable,can be used to recover the real resistivity model with an acceptable effi ciency.展开更多
For many years, the “short excavation and short exploration” excavation mode has been mainly used in the underground tunnel excavation of coal mines, which is difficult to meet the needs of rapid tunnel excavation. ...For many years, the “short excavation and short exploration” excavation mode has been mainly used in the underground tunnel excavation of coal mines, which is difficult to meet the needs of rapid tunnel excavation. For this reason, CCTEG Xi’an Research Institute has innovatively proposed a new working mode of “long excavation and long exploration” using directional long drilling and borehole geophysical exploration. This method utilizes directional long boreholes that have already been constructed, and uses transient electromagnetic technology in the borehole to detect the radial range of 30 meters and the depth exceeding 1000 meters of the borehole, ultimately forming a three-dimensional imaging of the entire spatial geological anomaly body, providing reliable technical support for the safety and long-term excavation of the tunnel. This paper introduces the application which is a long-distance advanced detection of 1026 m. .展开更多
基金the National Key Research and Development Program of China(No.2016YFC060110403).
文摘Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fourier transform related to the electromagnetic response in the frequency and time domains becomes a sine or cosine transform under the excitation of downward-step current.We established a transformation matrix based on the digital fi ltering calculation for the sine transform,and then the frequency domain projection of the TEM data was determined from the linear transformation system using the smoothing constrained least squares inversion method,in which only the imaginary part was used to maintain the TEM data transformation equivalence in the bidirectional projection.Thus,the time-domain TEM inversion problem was indirectly and effectively solved in the frequency domain.In the 3D inversion of the transformed frequency-domain data,the limited-memory Broyden–Fletcher–Goldfarb–Shannoquasi–Newton(L-BFGS)method was used and modifi ed with a restart strategy to adjust the regularization parameter when the algorithm tended to a local minimum.Synthetic data tests showed that our domain transformation method can stably project the TEM data into the frequency domain with very high accuracy;furthe rmore,the 3D inversion of the transformed frequency-domain data is stable,can be used to recover the real resistivity model with an acceptable effi ciency.
文摘For many years, the “short excavation and short exploration” excavation mode has been mainly used in the underground tunnel excavation of coal mines, which is difficult to meet the needs of rapid tunnel excavation. For this reason, CCTEG Xi’an Research Institute has innovatively proposed a new working mode of “long excavation and long exploration” using directional long drilling and borehole geophysical exploration. This method utilizes directional long boreholes that have already been constructed, and uses transient electromagnetic technology in the borehole to detect the radial range of 30 meters and the depth exceeding 1000 meters of the borehole, ultimately forming a three-dimensional imaging of the entire spatial geological anomaly body, providing reliable technical support for the safety and long-term excavation of the tunnel. This paper introduces the application which is a long-distance advanced detection of 1026 m. .
