The Macao Science Satellite-1(known as MSS-1)is the first scientific exploration satellite that was designed to measure the Earth's low latitude magnetic field at high resolution and with high precision by collect...The Macao Science Satellite-1(known as MSS-1)is the first scientific exploration satellite that was designed to measure the Earth's low latitude magnetic field at high resolution and with high precision by collecting data in a near-equatorial orbit.Magnetic field data from MSS-1's onboard Vector Fluxgate Magnetometer(VFM),collected at a sample rate of 50 Hz,allows us to detect and investigate sources of magnetic data contamination,from DC to relevant Nyquist frequency.Here we report two types of artificial disturbances in the VFM data.One is V-shaped events concentrated at night,with frequencies sweeping from the Nyquist frequency down to zero and back up.The other is 5-Hz events(ones that exhibit a distinct 5 Hz spectrum peak);these events are always accompanied by intervals of spiky signals,and are clearly related to the attitude control of the satellite.Our analyses show that VFM noise levels in daytime are systematically lower than in nighttime.The daily average noise levels exhibit a period of about 52 days.The V-shaped events are strongly correlated with higher VFM noise levels.展开更多
Source properties and stress fields are critical to understand fundamental mechanisms for fluid-induced earthquakes.In this study,we identify the focal mechanism solutions(FMSs)of 360 earthquakes with local magnitude ...Source properties and stress fields are critical to understand fundamental mechanisms for fluid-induced earthquakes.In this study,we identify the focal mechanism solutions(FMSs)of 360 earthquakes with local magnitude M_(L)≥1.5 in the Changning shale gas field from January 2016 to May 2017 by fitting three-component waveforms.We then constrain the directions of the maximum horizontal stress(σ_(H_(max)))for four dense earthquake clusters using the stress tensor inversion method.The stress drops of 121 earthquakes with M_(L)≥1.5 are calculated using the spectral ratio method.We examine the spatiotemporal heterogeneity of stress field,and discuss the cause of non-double-couple(non-DC)components in seismicity clusters.Following the Mohr-Coulomb criterion,we estimate the fluid overpressure thresholds from FMS for different seismic clusters,providing insights into potential physical mechanisms for induced seismicity.The FMS results indicate that shallow reverse earthquakes,with steep dip angles,characterize most events.The source mechanisms of earthquakes with M_(L)≥1.5 are dominated by DC components(>70%),but several earthquakes with M_(L)>3.0 and the microseismic events nearby during injection period display significant non-DC components(>30%).Stress inversion results reveal that the σ_(H_(max)) direction ranges from 120°to 128°.Stress drops of earthquakes range between 0.10 and 64.49 MPa,with high values occurring on reverse faults situated at a greater distance from the shale layer,accompanied by a moderate rotation(≤25°)in the trend of σ_(H_(max)).The seismic clusters close to the shale layer exhibit low fluid overpressure thresholds,prone to being triggered by high pore-pressure fluid.The integrated results suggest that the diffusion of high pore pressures is likely to be the primary factor for observed earthquakes.The present results are expected to offer valuable insights into the origin of anomalous seismicity near the shale gas sites.展开更多
This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture ...This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.展开更多
In low-permeability geothermal reservoirs,hydro-shearing of pre-existing natural fractures plays a crucial role in improving connectivity between injection and production wells,thereby enhancing heat extraction effici...In low-permeability geothermal reservoirs,hydro-shearing of pre-existing natural fractures plays a crucial role in improving connectivity between injection and production wells,thereby enhancing heat extraction efficiency.This process increases fracture conductivity through dilation caused by injectioninduced slip;however,it also carries the risk of inducing seismic events,posing significant challenges for geothermal operations.This study employs a coupled hydro-mechanical numerical model based on the boundary element method to simulate hydro-shearing under two distinct fluid injection scenarios:(1)monotonic injection and(2)cyclic injection regulated by a traffic light system(TLS).The model assesses the effectiveness of these injection regimes in enhancing fracture conductivity while mitigating seismic hazards.Results indicate that monotonic injection frequently triggers a cascade of seismic events,disrupting pressure and stress distributions on nearby faults and resulting in complex seismic and aseismic interactions.In contrast,TLS-regulated cyclic injection,when carefully managed,promotes stable slip behavior and improves fracture conductivity.This approach proves particularly effective over extended durations during the simultaneous stimulation of two parallel faults.However,in multi-stage stimulation scenariosdwhere natural fractures are stimulated sequentiallydTLS-based cyclic injection,while more efficient at enhancing conductivity,may increase seismicity risk with prolonged application,thereby limiting its safe operational window.展开更多
In subsurface projects where the host rock is of low permeability,fractures play an important role in fluid circulation.Both the geometrical and mechanical properties of the fracture are relevant to the permeability o...In subsurface projects where the host rock is of low permeability,fractures play an important role in fluid circulation.Both the geometrical and mechanical properties of the fracture are relevant to the permeability of the fracture.To evaluate this relationship,we numerically generated self-affine fractures reproducing the scaling relationship of the power spectral density(PSD)of the measured fracture surfaces.The fractures were then subjected to a uniform and stepwise increase in normal stress.A fast Fourier transform(FFT)-based elastic contact model was used to simulate the fracture closure.The evolution of fracture contact area,fracture closure,and fracture normal stiffness were determined throughout the whole process.In addition,the fracture permeability at each step was calculated by the local cubic law(LCL).The influences of roughness exponent and correlation length on the fracture hydraulic and mechanical behaviors were investigated.Based on the power law of normal stiffness versus normal stress,the corrected cubic law and the linear relationship between fracture closure and mechanical aperture were obtained from numerical modeling of a set of fractures.Then,we derived a fracture normal stiffness-permeability equation which incorporates fracture geometric parameters such as the root-mean-square(RMS),roughness exponent,and correlation length,which can describe the fracture flow under an effective medium regime and a percolation regime.Finally,we interpreted the flow transition behavior from the effective medium regime to the percolation regime during fracture closure with the established stiffness-permeability function.展开更多
Understanding the hydromechanical behavior and permeability stress sensitivity of hydraulic fractures is fundamental for geotechnical applications associated with fluid injection.This paper presents a three-dimensiona...Understanding the hydromechanical behavior and permeability stress sensitivity of hydraulic fractures is fundamental for geotechnical applications associated with fluid injection.This paper presents a three-dimensional(3D)benchmark model of a laboratory experiment on graywacke to examine the dynamic hydraulic fracturing process under a polyaxial stress state.In the numerical model,injection pressures after breakdown(postbreakdown)are varied to study the impact on fracture growth.The fluid pressure front and crack front are identified in the numerical model to analyze the dynamic relationship between fluid diffusion and fracture propagation.Following the hydraulic fracturing test,the polyaxial stresses are rotated to investigate the influence of the stress field rotation on the fracture slip behavior and permeability.The results show that fracture propagation guides fluid diffusion under a high postbreakdown injection pressure.The crack front runs ahead of the fluid pressure front.Under a low postbreakdown injection pressure,the fluid pressure front gradually reaches the crack front,and fluid diffusion is the main driving factor of fracture propagation.Under polyaxial stress conditions,fluid injection not only opens tensile fractures but also induces hydroshearing.When the polyaxial stress is rotated,the fracture slip direction of a fully extended fracture is consistent with the shear stress direction.The fracture slip direction of a partly extended fracture is influenced by the increase in shear stress.Normal stress affects the permeability evolution by changing the average mechanical aperture.Shear stress can induce shearing and sliding on the fracture plane,thereby increasing permeability.展开更多
INTRODUCTION.On May 1st,2024,around 2:10 a.m.,a catastrophic collapse occurred along the Meilong Expressway near Meizhou City,Guangdong Province,China,at coordinates 24°29′24″N and 116°40′25″E.This colla...INTRODUCTION.On May 1st,2024,around 2:10 a.m.,a catastrophic collapse occurred along the Meilong Expressway near Meizhou City,Guangdong Province,China,at coordinates 24°29′24″N and 116°40′25″E.This collapse resulted in a pavement failure of approximately 17.9 m in length and covering an area of about 184.3 m^(2)(Chinanews,2024).展开更多
Purpose–This study solves the key problem that the static level monitoring is susceptible to temperature interference and affects the accuracy in slope instability/deformation monitoring.The purpose is to develop a r...Purpose–This study solves the key problem that the static level monitoring is susceptible to temperature interference and affects the accuracy in slope instability/deformation monitoring.The purpose is to develop a reliable temperature compensation method for the system,improve the accuracy of slope stability monitoring and provide support for improving the safety and safety monitoring of engineering spoil slope and other projects.Design/methodology/approach–Combined with theoretical analysis and experimental verification,the temperature compensation method is explored.The working principle of the hydrostatic leveling monitoring system is analyzed and the data processing formula,the temperature error calculation formula and the calculation formula for eliminating the error settlement value are derived.The temperature compensation method is established and verified by the field test of the engineering spoil slope which is disturbed by a debris flow.Findings–The experimental results show that this method can reduce the error of the static level monitoring system by about 40%.The field test shows that the fluctuation of slope settlement monitoring value is reduced after temperature compensation and the monitoring value is consistent with the actual situation,which has certain practicability.Originality/value–The originality of this study is to derive a theoretical formula for quantifying/eliminating temperature errors in static leveling and to establish a practical temperature compensation method.The accuracy of the system is improved,which provides a reference for slope stability monitoring under complex environment(especially railway geotechnical engineering)and promotes the development of precision monitoring technology.展开更多
In this study,we employed Bayesian inversion coupled with the summation-by-parts and simultaneousapproximation-term(SBP-SAT)forward simulation method to elucidate the mechanisms behind mininginduced seismic events cau...In this study,we employed Bayesian inversion coupled with the summation-by-parts and simultaneousapproximation-term(SBP-SAT)forward simulation method to elucidate the mechanisms behind mininginduced seismic events caused by fault slip and their potential effects on rockbursts.Through Bayesian inversion,it is determined that the sources near fault FQ14 have a significant shear component.Additionally,we analyzed the stress and displacement fields of high-energy events,along with the hypocenter distribution of aftershocks,which aided in identifying the slip direction of the critically stressed fault FQ14.We also performed forward modeling to capture the complex dynamics of fault slip under varying friction laws and shear fracture modes.The selection of specific friction laws for fault slip models was based on their ability to accurately replicate observed slip behavior under various external loading conditions,thereby enhancing the applicability of our findings.Our results suggest that the slip behavior of fault FQ14 can be effectively understood by comparing different scenarios.展开更多
To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main compon...To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main components:a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state,a quantitative relationship between critical irreversible deformation and complex stress state,and evolution characteristics of strength parameters.The proposed model is implemented in a self-developed numerical code,i.e.CASRock.The reliability of the model is validated through experiments.It is indicated that the time-dependent fracturing potential index(xTFPI)at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage.The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress,thereby highlighting the 3D stress-dependent characteristic of the model.Finally,the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed.展开更多
Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et ...Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et al.,2022,2023).The North Atlantic region is a prime example of the interaction between plate tectonic movements and thermal instabilities in the Earth's mantle.The opening of the Labrador Sea/Baffin Bay and the North Atlantic,the widespread volcanism and the localized uplift of the topography in Greenland and the North Atlantic are traditionally attributed to the thermal effect of the Iceland mantle plume.展开更多
Satellite Interferometric Synthetic Aperture Radar(InSAR)is widely used for topographic,geological and natural resource investigations.However,most of the existing InSAR studies of ground deformation are based on rela...Satellite Interferometric Synthetic Aperture Radar(InSAR)is widely used for topographic,geological and natural resource investigations.However,most of the existing InSAR studies of ground deformation are based on relatively short periods and single sensors.This paper introduces a new multi-sensor InSAR time series data fusion method for time-overlapping and time-interval datasets,to address cases when partial overlaps and/or temporal gaps exist.A new Power Exponential Knothe Model(PEKM)fits and fuses overlaps in the deformation curves,while a Long Short-Term Memory(LSTM)neural network predicts and fuses any temporal gaps in the series.Taking the city of Wuhan(China)as experiment area,COSMO-SkyMed(2011-2015),TerraSAR-X(2015-2019)and Sentinel-1(2019-2021)SAR datasets were fused to map long-term surface deformation over the last decade.An independent 2011-2020 InSAR time series analysis based on 230 COSMO-SkyMed scenes was also used as reference for comparison.The correlation coefficient between the results of the fusion algorithm and the reference data is 0.87 in the time overlapping region and 0.97 in the time-interval dataset.The correlation coefficient of the overall results is 0.78,which fully demonstrates that the algorithm proposed in our paper achieves a similar trend as the reference deformation curve.The experimental results are consistent with existing studies of surface deformation at Wuhan,demonstrating the accuracy of the proposed new fusion method to provide robust time series for the analysis of long-term land subsidence mechanisms.展开更多
A comprehensive understanding of shale’s bedding anisotropy is crucial for shale-related engineering activities,such as hydraulic fracturing,drilling and underground excavation.In this study,seven Brazilian tests wer...A comprehensive understanding of shale’s bedding anisotropy is crucial for shale-related engineering activities,such as hydraulic fracturing,drilling and underground excavation.In this study,seven Brazilian tests were conducted on shale samples at different bedding orientations with respect to the loading direction(0°,45°and 90°)and the disc end face(0°,45°and 90°).An acoustic emission(AE)system was employed to capture the evolution of damage and the temporal-spatial distribution of microcracks under splitting-tensile stress.The results show that the Brazilian tensile strength decreases with increasing bedding inclination with respect to the disc end face,while it increases with the angle between bedding and loading directions.Increasing the bedding inclination with respect to the end face facilitates the reduction in b value and enhances the shale’s resistance to microcrack growth during the loading process.Misalignment between the bedding orientation and the end face suppresses the growth of mixed tensile-shear microcracks,while reducing the bedding angle relative to the loading direction is beneficial for creating mixed tensile-shear and tensile cracks.The observed microscopic failure characteristics are attributed to the competing effects of bedding activation and breakage of shale matrix at different bedding inclinations.The temporal-spatial distribution of microcracks,characterized by AE statistics including the correlation dimension and spatial correlation length,illustrates that the fractal evolution of microcracks is independent of bedding anisotropy,whereas the spatial distribution shows a stronger correlation.The evolution features of correlation dimension and spatial correlation length could be potentially used as precursors for shale splitting failure.These findings may be useful for predicting rock mass instability and analyzing the causes of catastrophic rupture.展开更多
Life exists in the universe and therefore the astrophysical properties of the universe must be such that they allow the origin of life. We connect astrobiology and astrophysics via one astrobiological quantity—the pr...Life exists in the universe and therefore the astrophysical properties of the universe must be such that they allow the origin of life. We connect astrobiology and astrophysics via one astrobiological quantity—the probability of the origin of life. We show how this probability, if it is very low, will allow us to answer profound astrophysical questions such as the type of universe we live in, the fate of our universe, whether neutron stars, white and brown dwarfs evaporate and whether protons decay.展开更多
The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission will explore global dynamics of the magnetosphere under varying solar wind and interplane...The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions,and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere.Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission.Here,we describe current community efforts to prepare for SMILE,and the benefits and context various experiments that have explicitly expressed support for SMILE can offer.A dedicated group of international scientists representing many different experiment types and geographical locations,the Ground-based and Additional Science Working Group,is facilitating these efforts.Preparations include constructing an online SMILE Data Fusion Facility,the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar,and the consideration of particular observing strategies and spacecraft conjunctions.We anticipate growing interest and community engagement with the SMILE mission,and we welcome novel ideas and insights from the solar-terrestrial community.展开更多
基金supported by the National Key R&D Program of China(Grant2022YFF0503700)the National Natural Science Foundation of China(42474200 and 42174186)。
文摘The Macao Science Satellite-1(known as MSS-1)is the first scientific exploration satellite that was designed to measure the Earth's low latitude magnetic field at high resolution and with high precision by collecting data in a near-equatorial orbit.Magnetic field data from MSS-1's onboard Vector Fluxgate Magnetometer(VFM),collected at a sample rate of 50 Hz,allows us to detect and investigate sources of magnetic data contamination,from DC to relevant Nyquist frequency.Here we report two types of artificial disturbances in the VFM data.One is V-shaped events concentrated at night,with frequencies sweeping from the Nyquist frequency down to zero and back up.The other is 5-Hz events(ones that exhibit a distinct 5 Hz spectrum peak);these events are always accompanied by intervals of spiky signals,and are clearly related to the attitude control of the satellite.Our analyses show that VFM noise levels in daytime are systematically lower than in nighttime.The daily average noise levels exhibit a period of about 52 days.The V-shaped events are strongly correlated with higher VFM noise levels.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U20A20266 and 12302503)Scientific and technological research projects in Sichuan province(Grant No.2024NSFSC0973).
文摘Source properties and stress fields are critical to understand fundamental mechanisms for fluid-induced earthquakes.In this study,we identify the focal mechanism solutions(FMSs)of 360 earthquakes with local magnitude M_(L)≥1.5 in the Changning shale gas field from January 2016 to May 2017 by fitting three-component waveforms.We then constrain the directions of the maximum horizontal stress(σ_(H_(max)))for four dense earthquake clusters using the stress tensor inversion method.The stress drops of 121 earthquakes with M_(L)≥1.5 are calculated using the spectral ratio method.We examine the spatiotemporal heterogeneity of stress field,and discuss the cause of non-double-couple(non-DC)components in seismicity clusters.Following the Mohr-Coulomb criterion,we estimate the fluid overpressure thresholds from FMS for different seismic clusters,providing insights into potential physical mechanisms for induced seismicity.The FMS results indicate that shallow reverse earthquakes,with steep dip angles,characterize most events.The source mechanisms of earthquakes with M_(L)≥1.5 are dominated by DC components(>70%),but several earthquakes with M_(L)>3.0 and the microseismic events nearby during injection period display significant non-DC components(>30%).Stress inversion results reveal that the σ_(H_(max)) direction ranges from 120°to 128°.Stress drops of earthquakes range between 0.10 and 64.49 MPa,with high values occurring on reverse faults situated at a greater distance from the shale layer,accompanied by a moderate rotation(≤25°)in the trend of σ_(H_(max)).The seismic clusters close to the shale layer exhibit low fluid overpressure thresholds,prone to being triggered by high pore-pressure fluid.The integrated results suggest that the diffusion of high pore pressures is likely to be the primary factor for observed earthquakes.The present results are expected to offer valuable insights into the origin of anomalous seismicity near the shale gas sites.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB2390300)the National Natural Science Foundation of China(Grant No.42172292)Yinlin Ji is grateful for the support by the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(Contract No.VH-NG-1516).
文摘This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.
基金the financial support of the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(Contract number VHNG-1516).
文摘In low-permeability geothermal reservoirs,hydro-shearing of pre-existing natural fractures plays a crucial role in improving connectivity between injection and production wells,thereby enhancing heat extraction efficiency.This process increases fracture conductivity through dilation caused by injectioninduced slip;however,it also carries the risk of inducing seismic events,posing significant challenges for geothermal operations.This study employs a coupled hydro-mechanical numerical model based on the boundary element method to simulate hydro-shearing under two distinct fluid injection scenarios:(1)monotonic injection and(2)cyclic injection regulated by a traffic light system(TLS).The model assesses the effectiveness of these injection regimes in enhancing fracture conductivity while mitigating seismic hazards.Results indicate that monotonic injection frequently triggers a cascade of seismic events,disrupting pressure and stress distributions on nearby faults and resulting in complex seismic and aseismic interactions.In contrast,TLS-regulated cyclic injection,when carefully managed,promotes stable slip behavior and improves fracture conductivity.This approach proves particularly effective over extended durations during the simultaneous stimulation of two parallel faults.However,in multi-stage stimulation scenariosdwhere natural fractures are stimulated sequentiallydTLS-based cyclic injection,while more efficient at enhancing conductivity,may increase seismicity risk with prolonged application,thereby limiting its safe operational window.
基金supported by the China Postdoctoral Science Foundation Funded Project(Grant No.2023M740385)the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20233326)the support by the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(Contract No.VH-NG-1516).
文摘In subsurface projects where the host rock is of low permeability,fractures play an important role in fluid circulation.Both the geometrical and mechanical properties of the fracture are relevant to the permeability of the fracture.To evaluate this relationship,we numerically generated self-affine fractures reproducing the scaling relationship of the power spectral density(PSD)of the measured fracture surfaces.The fractures were then subjected to a uniform and stepwise increase in normal stress.A fast Fourier transform(FFT)-based elastic contact model was used to simulate the fracture closure.The evolution of fracture contact area,fracture closure,and fracture normal stiffness were determined throughout the whole process.In addition,the fracture permeability at each step was calculated by the local cubic law(LCL).The influences of roughness exponent and correlation length on the fracture hydraulic and mechanical behaviors were investigated.Based on the power law of normal stiffness versus normal stress,the corrected cubic law and the linear relationship between fracture closure and mechanical aperture were obtained from numerical modeling of a set of fractures.Then,we derived a fracture normal stiffness-permeability equation which incorporates fracture geometric parameters such as the root-mean-square(RMS),roughness exponent,and correlation length,which can describe the fracture flow under an effective medium regime and a percolation regime.Finally,we interpreted the flow transition behavior from the effective medium regime to the percolation regime during fracture closure with the established stiffness-permeability function.
基金supported by the Knowledge Innovation Program of Wuhan-Basic Research (Grant No.2022010801010159)support from the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES (Contract number VH-NG-1516)supported by the Swedish Radiation Safety Authority (Project SSM2020-2758).
文摘Understanding the hydromechanical behavior and permeability stress sensitivity of hydraulic fractures is fundamental for geotechnical applications associated with fluid injection.This paper presents a three-dimensional(3D)benchmark model of a laboratory experiment on graywacke to examine the dynamic hydraulic fracturing process under a polyaxial stress state.In the numerical model,injection pressures after breakdown(postbreakdown)are varied to study the impact on fracture growth.The fluid pressure front and crack front are identified in the numerical model to analyze the dynamic relationship between fluid diffusion and fracture propagation.Following the hydraulic fracturing test,the polyaxial stresses are rotated to investigate the influence of the stress field rotation on the fracture slip behavior and permeability.The results show that fracture propagation guides fluid diffusion under a high postbreakdown injection pressure.The crack front runs ahead of the fluid pressure front.Under a low postbreakdown injection pressure,the fluid pressure front gradually reaches the crack front,and fluid diffusion is the main driving factor of fracture propagation.Under polyaxial stress conditions,fluid injection not only opens tensile fractures but also induces hydroshearing.When the polyaxial stress is rotated,the fracture slip direction of a fully extended fracture is consistent with the shear stress direction.The fracture slip direction of a partly extended fracture is influenced by the increase in shear stress.Normal stress affects the permeability evolution by changing the average mechanical aperture.Shear stress can induce shearing and sliding on the fracture plane,thereby increasing permeability.
基金supported by the National Natural Science Foundation of China(Nos.42371094,41907253)partially supported by the Interdisciplinary Cultivation Program of Xidian University(No.21103240005)the Postdoctoral Fellowship Program of CPSF(No.GZB20240589)。
文摘INTRODUCTION.On May 1st,2024,around 2:10 a.m.,a catastrophic collapse occurred along the Meilong Expressway near Meizhou City,Guangdong Province,China,at coordinates 24°29′24″N and 116°40′25″E.This collapse resulted in a pavement failure of approximately 17.9 m in length and covering an area of about 184.3 m^(2)(Chinanews,2024).
基金funded by the Scientific Research Project of China Academy of Railway Sciences Group Co.,Ltd(No.2024YJ332 and No.2024QT005)Scientific Research Special Project of China State Railway Group Co.,Ltd(No.TICSTR-2024-Ⅳ-007).
文摘Purpose–This study solves the key problem that the static level monitoring is susceptible to temperature interference and affects the accuracy in slope instability/deformation monitoring.The purpose is to develop a reliable temperature compensation method for the system,improve the accuracy of slope stability monitoring and provide support for improving the safety and safety monitoring of engineering spoil slope and other projects.Design/methodology/approach–Combined with theoretical analysis and experimental verification,the temperature compensation method is explored.The working principle of the hydrostatic leveling monitoring system is analyzed and the data processing formula,the temperature error calculation formula and the calculation formula for eliminating the error settlement value are derived.The temperature compensation method is established and verified by the field test of the engineering spoil slope which is disturbed by a debris flow.Findings–The experimental results show that this method can reduce the error of the static level monitoring system by about 40%.The field test shows that the fluctuation of slope settlement monitoring value is reduced after temperature compensation and the monitoring value is consistent with the actual situation,which has certain practicability.Originality/value–The originality of this study is to derive a theoretical formula for quantifying/eliminating temperature errors in static leveling and to establish a practical temperature compensation method.The accuracy of the system is improved,which provides a reference for slope stability monitoring under complex environment(especially railway geotechnical engineering)and promotes the development of precision monitoring technology.
基金the Graduate Innovation Program of China University of Mining and Technology,the Fundamental Research Funds for the Central Universities(Grant No.2023WLKXJ017)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX23_2776)the Shandong Energy Group(Grant No.SNKJ2022BJ03-R28)。
文摘In this study,we employed Bayesian inversion coupled with the summation-by-parts and simultaneousapproximation-term(SBP-SAT)forward simulation method to elucidate the mechanisms behind mininginduced seismic events caused by fault slip and their potential effects on rockbursts.Through Bayesian inversion,it is determined that the sources near fault FQ14 have a significant shear component.Additionally,we analyzed the stress and displacement fields of high-energy events,along with the hypocenter distribution of aftershocks,which aided in identifying the slip direction of the critically stressed fault FQ14.We also performed forward modeling to capture the complex dynamics of fault slip under varying friction laws and shear fracture modes.The selection of specific friction laws for fault slip models was based on their ability to accurately replicate observed slip behavior under various external loading conditions,thereby enhancing the applicability of our findings.Our results suggest that the slip behavior of fault FQ14 can be effectively understood by comparing different scenarios.
基金supported by the National Natural Science Foundation of China(Grant No.52125903)the China Postdoctoral Science Foundation(Grant No.2023M730367)the Fundamental Research Funds for Central Public Welfare Research Institutes of China(Grant No.CKSF2023323/YT).
文摘To investigate the long-term stability of deep rocks,a three-dimensional(3D)time-dependent model that accounts for excavation-induced damage and complex stress state is developed.This model comprises three main components:a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state,a quantitative relationship between critical irreversible deformation and complex stress state,and evolution characteristics of strength parameters.The proposed model is implemented in a self-developed numerical code,i.e.CASRock.The reliability of the model is validated through experiments.It is indicated that the time-dependent fracturing potential index(xTFPI)at a given time during the attenuation creep stage shows a negative correlation with the extent of excavationinduced damage.The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress,thereby highlighting the 3D stress-dependent characteristic of the model.Finally,the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed.
文摘Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et al.,2022,2023).The North Atlantic region is a prime example of the interaction between plate tectonic movements and thermal instabilities in the Earth's mantle.The opening of the Labrador Sea/Baffin Bay and the North Atlantic,the widespread volcanism and the localized uplift of the topography in Greenland and the North Atlantic are traditionally attributed to the thermal effect of the Iceland mantle plume.
基金funded by the National Natural Science Foundation of China[grant number 42250610212]the China Scholarship Council[No.202106270150].
文摘Satellite Interferometric Synthetic Aperture Radar(InSAR)is widely used for topographic,geological and natural resource investigations.However,most of the existing InSAR studies of ground deformation are based on relatively short periods and single sensors.This paper introduces a new multi-sensor InSAR time series data fusion method for time-overlapping and time-interval datasets,to address cases when partial overlaps and/or temporal gaps exist.A new Power Exponential Knothe Model(PEKM)fits and fuses overlaps in the deformation curves,while a Long Short-Term Memory(LSTM)neural network predicts and fuses any temporal gaps in the series.Taking the city of Wuhan(China)as experiment area,COSMO-SkyMed(2011-2015),TerraSAR-X(2015-2019)and Sentinel-1(2019-2021)SAR datasets were fused to map long-term surface deformation over the last decade.An independent 2011-2020 InSAR time series analysis based on 230 COSMO-SkyMed scenes was also used as reference for comparison.The correlation coefficient between the results of the fusion algorithm and the reference data is 0.87 in the time overlapping region and 0.97 in the time-interval dataset.The correlation coefficient of the overall results is 0.78,which fully demonstrates that the algorithm proposed in our paper achieves a similar trend as the reference deformation curve.The experimental results are consistent with existing studies of surface deformation at Wuhan,demonstrating the accuracy of the proposed new fusion method to provide robust time series for the analysis of long-term land subsidence mechanisms.
基金supported by the National Natural Science Foundation of China (Grant No.52364004)the Basic Research Project of Guizhou University (Grant No.[2023]40)support by the Helmholtz Association’s Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES (Contract No.VH-NG-1516).
文摘A comprehensive understanding of shale’s bedding anisotropy is crucial for shale-related engineering activities,such as hydraulic fracturing,drilling and underground excavation.In this study,seven Brazilian tests were conducted on shale samples at different bedding orientations with respect to the loading direction(0°,45°and 90°)and the disc end face(0°,45°and 90°).An acoustic emission(AE)system was employed to capture the evolution of damage and the temporal-spatial distribution of microcracks under splitting-tensile stress.The results show that the Brazilian tensile strength decreases with increasing bedding inclination with respect to the disc end face,while it increases with the angle between bedding and loading directions.Increasing the bedding inclination with respect to the end face facilitates the reduction in b value and enhances the shale’s resistance to microcrack growth during the loading process.Misalignment between the bedding orientation and the end face suppresses the growth of mixed tensile-shear microcracks,while reducing the bedding angle relative to the loading direction is beneficial for creating mixed tensile-shear and tensile cracks.The observed microscopic failure characteristics are attributed to the competing effects of bedding activation and breakage of shale matrix at different bedding inclinations.The temporal-spatial distribution of microcracks,characterized by AE statistics including the correlation dimension and spatial correlation length,illustrates that the fractal evolution of microcracks is independent of bedding anisotropy,whereas the spatial distribution shows a stronger correlation.The evolution features of correlation dimension and spatial correlation length could be potentially used as precursors for shale splitting failure.These findings may be useful for predicting rock mass instability and analyzing the causes of catastrophic rupture.
文摘Life exists in the universe and therefore the astrophysical properties of the universe must be such that they allow the origin of life. We connect astrobiology and astrophysics via one astrobiological quantity—the probability of the origin of life. We show how this probability, if it is very low, will allow us to answer profound astrophysical questions such as the type of universe we live in, the fate of our universe, whether neutron stars, white and brown dwarfs evaporate and whether protons decay.
基金supported by Royal Society grant DHFR1211068funded by UKSA+14 种基金STFCSTFC grant ST/M001083/1funded by STFC grant ST/W00089X/1supported by NERC grant NE/W003309/1(E3d)funded by NERC grant NE/V000748/1support from NERC grants NE/V015133/1,NE/R016038/1(BAS magnetometers),and grants NE/R01700X/1 and NE/R015848/1(EISCAT)supported by NERC grant NE/T000937/1NSFC grants 42174208 and 41821003supported by the Research Council of Norway grant 223252PRODEX arrangement 4000123238 from the European Space Agencysupport of the AUTUMN East-West magnetometer network by the Canadian Space Agencysupported by NASA’s Heliophysics U.S.Participating Investigator Programsupport from grant NSF AGS 2027210supported by grant Dnr:2020-00106 from the Swedish National Space Agencysupported by the German Research Foundation(DFG)under number KR 4375/2-1 within SPP"Dynamic Earth"。
文摘The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions,and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere.Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission.Here,we describe current community efforts to prepare for SMILE,and the benefits and context various experiments that have explicitly expressed support for SMILE can offer.A dedicated group of international scientists representing many different experiment types and geographical locations,the Ground-based and Additional Science Working Group,is facilitating these efforts.Preparations include constructing an online SMILE Data Fusion Facility,the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar,and the consideration of particular observing strategies and spacecraft conjunctions.We anticipate growing interest and community engagement with the SMILE mission,and we welcome novel ideas and insights from the solar-terrestrial community.
