In crosswell observation of electromagnetic tomography, now there is no feasible way to calibrate the in situ radiation constant, while the effect of induced wave field always exists in observational data. Therefor...In crosswell observation of electromagnetic tomography, now there is no feasible way to calibrate the in situ radiation constant, while the effect of induced wave field always exists in observational data. Therefore the absorption coefficient obtained by a common used image reconstruction method is only a relative value. The consistency of tomograms in linked profiles inevitably is affected seriously. An improved equation involving the effect of induced wave field and an alternative tracing method to calculate the in situ radiation constant is proposed in the present paper. Based on the results from a series of parameter calibration performed in water and the experiments with rock samples, the standard meter readings of borehole electromagnetic systems, types EW—1 and JWQ—3, are accurately defined here. Additionally, frequency reduction and boundary smoothing of linked profiles are discussed. In research on groundwater prospecting in Tanggongta, Inner Mongolia, we used the above mentioned method and obtained the tomograms of linked profiles with good consistency. The absorption coefficient in the tomogram are not only reasonable and reliable, but also coincided with the result from rock parameter measurement. The depth, extension direction and water bearing structure of two aquifers were well detected. This result correctly guides hydrologic drilling there.展开更多
The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks i...The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.展开更多
文摘In crosswell observation of electromagnetic tomography, now there is no feasible way to calibrate the in situ radiation constant, while the effect of induced wave field always exists in observational data. Therefore the absorption coefficient obtained by a common used image reconstruction method is only a relative value. The consistency of tomograms in linked profiles inevitably is affected seriously. An improved equation involving the effect of induced wave field and an alternative tracing method to calculate the in situ radiation constant is proposed in the present paper. Based on the results from a series of parameter calibration performed in water and the experiments with rock samples, the standard meter readings of borehole electromagnetic systems, types EW—1 and JWQ—3, are accurately defined here. Additionally, frequency reduction and boundary smoothing of linked profiles are discussed. In research on groundwater prospecting in Tanggongta, Inner Mongolia, we used the above mentioned method and obtained the tomograms of linked profiles with good consistency. The absorption coefficient in the tomogram are not only reasonable and reliable, but also coincided with the result from rock parameter measurement. The depth, extension direction and water bearing structure of two aquifers were well detected. This result correctly guides hydrologic drilling there.
基金jointly supported by the project of Chinese National Natural Science Foundation(42107485)National Key R&D Program(2020YFC1512400,2018YFC800804)China Geological Survey(DD20190282,DD20221734,and DD20230323)。
文摘The construction of modern livable cities faces challenges in karst areas,including ground collapse and engineering problems.Wuhan,with a population of 13.74×10^(6) and approximately 1161 km^(2)of soluble rocks in the urban area of 8569.15 km^(2),predominantly consists of concealed karst areas where occasional ground collapse events occur,posing significant threats to underground engineering projects.To address these challenges,a comprehensive geological survey was conducted in Wuhan,focusing on major karstrelated issues.Geophysical methods offer advantages over drilling in detecting concealed karst areas due to their efficiency,non-destructiveness,and flexibility.This paper reviewed the karst geological characteristics in Wuhan and the geophysical exploration methods for karst,selected eight effective geophysical methods for field experimentation,evaluated their suitability,and proposed method combinations for different karst scenarios.The results show that different geophysical methods have varying applicability for karst detection in Wuhan,and combining multiple methods enhances detection effectiveness.The specific recommendations for method combinations provided in this study serve as a valuable reference for karst detection in Wuhan.
