In this present context, mathematical modeling of the propagation of surface waves in a fluid saturated poro-elastic medium under the influence of initial stress has been considered using time dependent higher order f...In this present context, mathematical modeling of the propagation of surface waves in a fluid saturated poro-elastic medium under the influence of initial stress has been considered using time dependent higher order finite difference method (FDM). We have proved that the accuracy of this finite-difference scheme is 2M when we use 2nd order time domain finite-difference and 2M-th order space domain finite-difference. It also has been shown that the dispersion curves of Love waves are less dispersed for higher order FDM than of lower order FDM. The effect of initial stress, porosity and anisotropy of the layer in the propagation of Love waves has been studied here. The numerical results have been shown graphically. As a particular case, the phase velocity in a non porous elastic solid layer derived in this paper is in perfect agreement with that of Liu et al. (2009).展开更多
This paper is based on the surface wave seismogram of South Sandwich Island earthquake(Ms=6.4) recorded by Antarctic General Bernardo O'Higgins Station. We computed a group velocity dispersion of Love surface wave...This paper is based on the surface wave seismogram of South Sandwich Island earthquake(Ms=6.4) recorded by Antarctic General Bernardo O'Higgins Station. We computed a group velocity dispersion of Love surface wave and obtained lithosphere structure by using the method of the matchedfilter frequencytime analysis and grid dispersion inversion. Our result shows that crust structure below Antarctic Peninsula may be divided into three layers and their thickness are respectively 5 km,8 km and 10 km. Upper mantle velocity is 5.32 km/s and gradually changes into 5.11 4.9 km/s below 53 km.The mininum velocity is 4.8 km/s. It can be referred that Antarctic mantle is also of layered structure.展开更多
Steel-concrete composite structures(SCCS)have been widely used as primary load-bearing components in large-scale civil infrastructures.As the basis of the co-working ability of steel plate and concrete,the bonding sta...Steel-concrete composite structures(SCCS)have been widely used as primary load-bearing components in large-scale civil infrastructures.As the basis of the co-working ability of steel plate and concrete,the bonding status plays an essential role in guaranteeing the structural performance of SCCS.Accordingly,efficient non-destructive testing(NDT)on interfacial debondings in SCCS has become a prominent research area.Multi-channel analysis of surface waves(MASW)has been validated as an effective NDT technique for interfacial debonding detection for SCCS.However,the feasibility of MASW must be validated using experimental measurements.This study establishes a high-frequency data synchronous acquisition system with 32 channels to perform comparative verification experiments in depth.First,the current sensing approaches for high-frequency vibration and stress waves are summarized.Secondly,three types of contact sensors,namely,piezoelectric lead-zirconate-titanate(PZT)patches,accelerometers,and ultrasonic transducers,are selected for MASW measurement.Then,the selection and optimization of the force hammer head are performed.Comparative experiments are carried out for the optimal selection of ultrasonic transducers,PZT patches,and accelerometers for MASW measurement.In addition,the influence of different pasting methods on the output signal of the sensor array is discussed.Experimental results indicate that optimized PZT patches,acceleration sensors,and ultrasonic transducers can provide efficient data acquisition for MASW-based non-destructive experiments.The research findings in this study lay a solid foundation for analyzing the recognition accuracy of contact MASW measurement using different sensor arrays.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
Shallow surface wave methods are mostly used for investigation of the surface velocity structure in environmental and engineering geophysics in non-desert areas. For the special geological features of the Takelamagan ...Shallow surface wave methods are mostly used for investigation of the surface velocity structure in environmental and engineering geophysics in non-desert areas. For the special geological features of the Takelamagan Desert area, we use the multi-channel analysis of surface wave （MASW） method to process multi-channel shallow surface wave records to determine the near surface velocity structure in the desert area. We also process, analyze, and compare the surface waves in many-trace records extracted from the oil exploration shot gathers in the area. We show that the MASW method can determine detailed shallow velocity structure in desert areas and the many-trace records can be used to get detailed deep geological structure. The combination of the two different datasets can obtain the exact velocity structure upper 60 m depth in the survey area.展开更多
High-resolution shallow seismic methods are the most widely used geophysical methods in near surface characterization. However, in many cases interpreting the seismic images can be misleading. In this article, we pres...High-resolution shallow seismic methods are the most widely used geophysical methods in near surface characterization. However, in many cases interpreting the seismic images can be misleading. In this article, we present three case studies where results from P-wave seismic reflection, SH-wave seismic reflection, and multi-channel analysis of surface wave （MASW） surveys were incorrectly interpreted because of inadequate constraints on either the surveyed sites surface or subsurface conditions. A P-wave reflection survey feature was first interpreted as a shallow fault zone but it was later determined to result from a high level of background noise as the acquisition passed through a road intersection. A SH-wave seismic reflection survey feature was interpreted to be a reverse dip-slip fault but targeted drilling showed it was deep local erosion into the bedrock surface. Finally, in an MASW survey, a steeply dipping feature was first interpreted as a bedrock valley. However, later exploratory drilling showed the feature to be a shallow layer of very soft lake sediment that severely damped most of the applied surface wave frequency band. Although initial interpretations were incorrect, they stimulated discussions among geophysicists and geologists and underscored the need for meaningful cooperation and discourse between the scientists before, during, and after geophysical data acquisition.展开更多
文摘In this present context, mathematical modeling of the propagation of surface waves in a fluid saturated poro-elastic medium under the influence of initial stress has been considered using time dependent higher order finite difference method (FDM). We have proved that the accuracy of this finite-difference scheme is 2M when we use 2nd order time domain finite-difference and 2M-th order space domain finite-difference. It also has been shown that the dispersion curves of Love waves are less dispersed for higher order FDM than of lower order FDM. The effect of initial stress, porosity and anisotropy of the layer in the propagation of Love waves has been studied here. The numerical results have been shown graphically. As a particular case, the phase velocity in a non porous elastic solid layer derived in this paper is in perfect agreement with that of Liu et al. (2009).
文摘This paper is based on the surface wave seismogram of South Sandwich Island earthquake(Ms=6.4) recorded by Antarctic General Bernardo O'Higgins Station. We computed a group velocity dispersion of Love surface wave and obtained lithosphere structure by using the method of the matchedfilter frequencytime analysis and grid dispersion inversion. Our result shows that crust structure below Antarctic Peninsula may be divided into three layers and their thickness are respectively 5 km,8 km and 10 km. Upper mantle velocity is 5.32 km/s and gradually changes into 5.11 4.9 km/s below 53 km.The mininum velocity is 4.8 km/s. It can be referred that Antarctic mantle is also of layered structure.
基金National Natural Science Foundation of China under Grant (Nos.52192662,52020105005,51908320)the Beijing Nova Program under Grant No.20220484012+1 种基金the Interdisciplinary Research Project for Young Teachers of USTB (Fundamental Research Funds for the Central Universities,FRF-IDRY-22-013)the Key Laboratory for Intelligent Infrastructure and Monitoring of Fujian Province (Huaqiao University,IIM-01-05)。
文摘Steel-concrete composite structures(SCCS)have been widely used as primary load-bearing components in large-scale civil infrastructures.As the basis of the co-working ability of steel plate and concrete,the bonding status plays an essential role in guaranteeing the structural performance of SCCS.Accordingly,efficient non-destructive testing(NDT)on interfacial debondings in SCCS has become a prominent research area.Multi-channel analysis of surface waves(MASW)has been validated as an effective NDT technique for interfacial debonding detection for SCCS.However,the feasibility of MASW must be validated using experimental measurements.This study establishes a high-frequency data synchronous acquisition system with 32 channels to perform comparative verification experiments in depth.First,the current sensing approaches for high-frequency vibration and stress waves are summarized.Secondly,three types of contact sensors,namely,piezoelectric lead-zirconate-titanate(PZT)patches,accelerometers,and ultrasonic transducers,are selected for MASW measurement.Then,the selection and optimization of the force hammer head are performed.Comparative experiments are carried out for the optimal selection of ultrasonic transducers,PZT patches,and accelerometers for MASW measurement.In addition,the influence of different pasting methods on the output signal of the sensor array is discussed.Experimental results indicate that optimized PZT patches,acceleration sensors,and ultrasonic transducers can provide efficient data acquisition for MASW-based non-destructive experiments.The research findings in this study lay a solid foundation for analyzing the recognition accuracy of contact MASW measurement using different sensor arrays.
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.
文摘Shallow surface wave methods are mostly used for investigation of the surface velocity structure in environmental and engineering geophysics in non-desert areas. For the special geological features of the Takelamagan Desert area, we use the multi-channel analysis of surface wave （MASW） method to process multi-channel shallow surface wave records to determine the near surface velocity structure in the desert area. We also process, analyze, and compare the surface waves in many-trace records extracted from the oil exploration shot gathers in the area. We show that the MASW method can determine detailed shallow velocity structure in desert areas and the many-trace records can be used to get detailed deep geological structure. The combination of the two different datasets can obtain the exact velocity structure upper 60 m depth in the survey area.
文摘High-resolution shallow seismic methods are the most widely used geophysical methods in near surface characterization. However, in many cases interpreting the seismic images can be misleading. In this article, we present three case studies where results from P-wave seismic reflection, SH-wave seismic reflection, and multi-channel analysis of surface wave （MASW） surveys were incorrectly interpreted because of inadequate constraints on either the surveyed sites surface or subsurface conditions. A P-wave reflection survey feature was first interpreted as a shallow fault zone but it was later determined to result from a high level of background noise as the acquisition passed through a road intersection. A SH-wave seismic reflection survey feature was interpreted to be a reverse dip-slip fault but targeted drilling showed it was deep local erosion into the bedrock surface. Finally, in an MASW survey, a steeply dipping feature was first interpreted as a bedrock valley. However, later exploratory drilling showed the feature to be a shallow layer of very soft lake sediment that severely damped most of the applied surface wave frequency band. Although initial interpretations were incorrect, they stimulated discussions among geophysicists and geologists and underscored the need for meaningful cooperation and discourse between the scientists before, during, and after geophysical data acquisition.
