We monitored the amplitude changes of coda transmission waves around 500 kHz across the frictional interface of a simulated 1. 5-meter-long fault during normal stress holding test.We find that the amplitude of coda tr...We monitored the amplitude changes of coda transmission waves around 500 kHz across the frictional interface of a simulated 1. 5-meter-long fault during normal stress holding test.We find that the amplitude of coda transmission waves increases with the logarithm of stationary contact time. Localized increase amounted to a level ranging from 4% to 16%along the fault is observed during the 1-hour experiment. We discuss that the frictional strength at mesoscopic scale,which is related to the amplitude of coda transmission waves,is responsible for the phenomenon. Combining the reported method with other complementary approaches will enhance the understanding of fault mechanism either at laboratory or on-site applications.展开更多
The paper studies CO2 degassing and controlling factors under the condition of contact metamorphism in the Shuangshan area, southern Tan-Lu fault belt and the method of calculating the amount of CO2 degassing. The res...The paper studies CO2 degassing and controlling factors under the condition of contact metamorphism in the Shuangshan area, southern Tan-Lu fault belt and the method of calculating the amount of CO2 degassing. The results show that the amount of CO2 degassing is controlled by the characteristics of the country rocks, including the thermal conductivity, penetrability, porosity and connectivity. Compositions, size and depth of intrusive rock also have an important influence on CO2 degassing, i.e., they generated numerous cracks in the country rocks, and thus allowed the easy flow and accumulation of fluids. The amount of CO2 flux in contact metamorphism is calculated quantitatively based on the metamorphic reaction and time-integrated fluid flux. The value （0.729- 2.446×10^4 mol/cm^2） of CO2 flux suggests that CO2 was provided mainly by the contact metamorphic reaction. The generation and releasing of CO2 are positively correlated with the degree of metamorphism, and XCO2 in fluids gradually increases from dolomite zone to calcite zone, but in the zone of grossular, fluid flux is the largest and XCO2 sharply decreases due to involvement of magmatic water. This study presents evidence that a large amount of industrial-scale CO2 can be produced during contact metamorphism. On the basis of theoretical and practical studies, a cone model has been proposed to response CO2 degassing for the contact metamorphism, and it can be used to explore CO2 accumulations beyond the oil-gas basins. This model can also be applied to the study of inorganic genesis of CO2 accumulations.展开更多
The geological and tectonic impact of the collision between the Congo Craton and the Pan-African Ridge of Central Africa was considerable, with the formation of various tectonic faults, fractures, dykes and folds. The...The geological and tectonic impact of the collision between the Congo Craton and the Pan-African Ridge of Central Africa was considerable, with the formation of various tectonic faults, fractures, dykes and folds. The present gravity analysis is based on the analysis of EGM 2008 gravity data using different operators. Oasis Montaj software was used to process the data. The Bouguer anomaly map was used to identify the main local and regional anomalies. In addition, maps of the horizontal and vertical gradients of the Tilt angle analytical signal revealed several short-wavelength anomalies such as folds, dykes, fractures and faults. The map of superimposed maxima was used to create the structural map of the study area. For its part, the quantitative study provided an opportunity to assess the depths at which the anomalies originated. The deepest anomalies are more than 17 km deep and lie to the south of the study area. Examination of these various maps reveals that the various geological faults mentioned above generally follow ENE-WSW, ESE-WNW, NE-SW, NW-SE, E-W and even N-S directions. All of these directions appear to be closely linked to the geological history of the region. It is quite clear that the study area was the site of intense tectonic movements caused by the collision between the Congo craton and the Pan-African chain of Central Africa.展开更多
In welded-contact boundary conditions, some stress components are not required to be continuous across the boundary between two elastic half-spaces. The purpose of this note is to study the modifications in the stress...In welded-contact boundary conditions, some stress components are not required to be continuous across the boundary between two elastic half-spaces. The purpose of this note is to study the modifications in the stress field of a long inclined strike-slip, dip-slip or tensile fault caused by the welded-contact boundary conditions across the interface between two elastic half-spaces. The Poisson’s ratios of the two half-spaces do not appear in the stress field of a strike-slip fault. In the case of a dip-slip fault, the Poisson’s ratio of the half-space in which the fault lies, has a significant influence on the stress field across the interface. However, for a tensile fault, the modification in the stress field is significantly affected by the Poisson’s ratios of both the half-spaces.展开更多
A 3-D soil-pipe nonlinear finite element model with contact element is suggested and the influences of the rupture mode, thickness and rigidity of overlying soil on the response of buried pipeline are analyzed. The nu...A 3-D soil-pipe nonlinear finite element model with contact element is suggested and the influences of the rupture mode, thickness and rigidity of overlying soil on the response of buried pipeline are analyzed. The numerical results show that the soil rupture mode determines the location of the large deformation or failure of the pipeline, and the plastic de- formation of the pipeline occurs at the zone where the plastic deformation or rupture of the overlying soil appears. When the fault dip angle on bedrock is near 90°, two plastic deformation sections of the pipeline appear with the development of overlying soil rupture. And the thicker the overlying soil is, the longer the plastic deformation length of the pipeline is and the less its strain is. The plastic deformation length of the pipeline decreases while its maximum strain increases with the rigidity of overlying soil increasing.展开更多
Dynamic contact theory is applied to simulate the sliding of surface fault. Finite element method is used to analyze the effect of surface fault to site ground motions. Calculated results indicate that amplification e...Dynamic contact theory is applied to simulate the sliding of surface fault. Finite element method is used to analyze the effect of surface fault to site ground motions. Calculated results indicate that amplification effect is obvious in the area near surface fault, especially on the site that is in the downside fault. The results show that the effect of surface fault should be considered when important structure is constructed in the site with surface fault.展开更多
The industrial power systems are moving to digital networks,and unmanned systems are increasing recently with the technological development of information and communication technology.In particular,reliability of syst...The industrial power systems are moving to digital networks,and unmanned systems are increasing recently with the technological development of information and communication technology.In particular,reliability of system operation is very important for stable power supply.Most industrial power distribution facilities use a 154 kV or 22.9 kV extra HV(high voltage)power system,and a special monitoring system is required because a large loss occurs when an error occurs in the power facility in the field.Although digital protection relay(IED;intelligent electronic device)and FR(fault recorder)are applied to the field to protect the power system,various improvement activities are still ongoing.In this paper,a 22.9 kV high-voltage panel and its test bed,which are widely used in railway stations,tunnels,substations and large plants,were tested as test subjects.The developed fault detection system automatically starts the AL(auto-lock)circuit or outputs an alarm signal to user by monitoring in real time problems such as CT(current transformer)-open and poor-contact that the existing digital protection relay cannot cover.In addition,it is intended to increase the safety and reliability of the power system by blocking various accidents in the system in advance and accurately analyzing the causes of faults with the developed fault detection system.展开更多
基金sponsored by the National Natural Science Foundation of China(41874061)
文摘We monitored the amplitude changes of coda transmission waves around 500 kHz across the frictional interface of a simulated 1. 5-meter-long fault during normal stress holding test.We find that the amplitude of coda transmission waves increases with the logarithm of stationary contact time. Localized increase amounted to a level ranging from 4% to 16%along the fault is observed during the 1-hour experiment. We discuss that the frictional strength at mesoscopic scale,which is related to the amplitude of coda transmission waves,is responsible for the phenomenon. Combining the reported method with other complementary approaches will enhance the understanding of fault mechanism either at laboratory or on-site applications.
基金supported by grants from the Natural Science Foundation of China(grant Nos:40473021 and 40472074)the National Basic Research Program of China(grant No:2003CB214600).
文摘The paper studies CO2 degassing and controlling factors under the condition of contact metamorphism in the Shuangshan area, southern Tan-Lu fault belt and the method of calculating the amount of CO2 degassing. The results show that the amount of CO2 degassing is controlled by the characteristics of the country rocks, including the thermal conductivity, penetrability, porosity and connectivity. Compositions, size and depth of intrusive rock also have an important influence on CO2 degassing, i.e., they generated numerous cracks in the country rocks, and thus allowed the easy flow and accumulation of fluids. The amount of CO2 flux in contact metamorphism is calculated quantitatively based on the metamorphic reaction and time-integrated fluid flux. The value （0.729- 2.446×10^4 mol/cm^2） of CO2 flux suggests that CO2 was provided mainly by the contact metamorphic reaction. The generation and releasing of CO2 are positively correlated with the degree of metamorphism, and XCO2 in fluids gradually increases from dolomite zone to calcite zone, but in the zone of grossular, fluid flux is the largest and XCO2 sharply decreases due to involvement of magmatic water. This study presents evidence that a large amount of industrial-scale CO2 can be produced during contact metamorphism. On the basis of theoretical and practical studies, a cone model has been proposed to response CO2 degassing for the contact metamorphism, and it can be used to explore CO2 accumulations beyond the oil-gas basins. This model can also be applied to the study of inorganic genesis of CO2 accumulations.
文摘The geological and tectonic impact of the collision between the Congo Craton and the Pan-African Ridge of Central Africa was considerable, with the formation of various tectonic faults, fractures, dykes and folds. The present gravity analysis is based on the analysis of EGM 2008 gravity data using different operators. Oasis Montaj software was used to process the data. The Bouguer anomaly map was used to identify the main local and regional anomalies. In addition, maps of the horizontal and vertical gradients of the Tilt angle analytical signal revealed several short-wavelength anomalies such as folds, dykes, fractures and faults. The map of superimposed maxima was used to create the structural map of the study area. For its part, the quantitative study provided an opportunity to assess the depths at which the anomalies originated. The deepest anomalies are more than 17 km deep and lie to the south of the study area. Examination of these various maps reveals that the various geological faults mentioned above generally follow ENE-WSW, ESE-WNW, NE-SW, NW-SE, E-W and even N-S directions. All of these directions appear to be closely linked to the geological history of the region. It is quite clear that the study area was the site of intense tectonic movements caused by the collision between the Congo craton and the Pan-African chain of Central Africa.
文摘In welded-contact boundary conditions, some stress components are not required to be continuous across the boundary between two elastic half-spaces. The purpose of this note is to study the modifications in the stress field of a long inclined strike-slip, dip-slip or tensile fault caused by the welded-contact boundary conditions across the interface between two elastic half-spaces. The Poisson’s ratios of the two half-spaces do not appear in the stress field of a strike-slip fault. In the case of a dip-slip fault, the Poisson’s ratio of the half-space in which the fault lies, has a significant influence on the stress field across the interface. However, for a tensile fault, the modification in the stress field is significantly affected by the Poisson’s ratios of both the half-spaces.
基金supported by the National Natural Science Foundation of China (50778166)the Basic Research Fund of State Level Research Institutes,Institute of Engineering Mechanics of China Earthquake Administration (2007B09)the National Scientific and Technological Support Project from Min-istry of Science and Technology (2006BAC13B02)
文摘A 3-D soil-pipe nonlinear finite element model with contact element is suggested and the influences of the rupture mode, thickness and rigidity of overlying soil on the response of buried pipeline are analyzed. The numerical results show that the soil rupture mode determines the location of the large deformation or failure of the pipeline, and the plastic de- formation of the pipeline occurs at the zone where the plastic deformation or rupture of the overlying soil appears. When the fault dip angle on bedrock is near 90°, two plastic deformation sections of the pipeline appear with the development of overlying soil rupture. And the thicker the overlying soil is, the longer the plastic deformation length of the pipeline is and the less its strain is. The plastic deformation length of the pipeline decreases while its maximum strain increases with the rigidity of overlying soil increasing.
文摘Dynamic contact theory is applied to simulate the sliding of surface fault. Finite element method is used to analyze the effect of surface fault to site ground motions. Calculated results indicate that amplification effect is obvious in the area near surface fault, especially on the site that is in the downside fault. The results show that the effect of surface fault should be considered when important structure is constructed in the site with surface fault.
基金This study was conducted by the Ministry of Land,Infrastructure and Transport’s Research Project on Railway Technology-Projects(21RTRP-B146037-04).
文摘The industrial power systems are moving to digital networks,and unmanned systems are increasing recently with the technological development of information and communication technology.In particular,reliability of system operation is very important for stable power supply.Most industrial power distribution facilities use a 154 kV or 22.9 kV extra HV(high voltage)power system,and a special monitoring system is required because a large loss occurs when an error occurs in the power facility in the field.Although digital protection relay(IED;intelligent electronic device)and FR(fault recorder)are applied to the field to protect the power system,various improvement activities are still ongoing.In this paper,a 22.9 kV high-voltage panel and its test bed,which are widely used in railway stations,tunnels,substations and large plants,were tested as test subjects.The developed fault detection system automatically starts the AL(auto-lock)circuit or outputs an alarm signal to user by monitoring in real time problems such as CT(current transformer)-open and poor-contact that the existing digital protection relay cannot cover.In addition,it is intended to increase the safety and reliability of the power system by blocking various accidents in the system in advance and accurately analyzing the causes of faults with the developed fault detection system.
