During the electromagnetic railgun launch process,high temperature and high current conditions can lead to armature wear,affecting armature/rail contact and degrading launch performance.This paper starts with the anal...During the electromagnetic railgun launch process,high temperature and high current conditions can lead to armature wear,affecting armature/rail contact and degrading launch performance.This paper starts with the analysis of the metal liquid film formation at the armature/rail contact interface.1D and 3D models are developed based on the characteristic relational equation obtained from the melt liquid film model.These models incorporate thermodynamic equilibrium phase diagram,transient heat and mass transfer model,copper-aluminum alloy reaction model,nonlinear electrical conductivity relational equation and nonlinear thermal conductivity relational equation to analyze the temperature distribution and copper-aluminum intermetallic compounds(Cu-Al IMCs)formation in the melt liquid film.The wear mechanism and influence law of armature are explained in detail from different perspectives to un-derstand and predict the transition and gouging phenomena at the contact interface.The model's validity is confirmed by the results of electromagnetic launch experiments,providing insights for future structure design and material selection of the armature and rail.展开更多
Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margi...Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margin zone(MZ)to the slip central zone(CZ)of the fault gouge in the Beichuan-Yingxiu surface rupture zone of the Wenchuan Earthquake.Results show that the clay minerals contents increase from the MZ to CZ,and the quartz and plagioclase contents slight decrease.An increasing enrichment in Al_(2)O_(3),Fe_(2)O_(3),and K_(2)O are observed toward the CZ;the decomposition of quartz and plagioclase,as well as the depletion of Si O_(2),Ca O,Na_2O,and P_(2)O_(5)suggest that the alkaline-earth elements are carried away by the fluids.It can be explained that the stronger coseismic actions in the CZ allow more clay minerals to form,decompose quartz and plagioclase,and alter plagioclase to chlorite.The mass loss in the CZ is larger than that in MZ,which is maybe due to the more concentrated stress in the strongly deformed CZ,however other causes will not be excluded.展开更多
Fault zones are usually filled with fault gouge and accompanied by fault water.The coupled effect of fault gouge and water significantly impacts the slip behavior of the fault,which may weaken the fault structure and ...Fault zones are usually filled with fault gouge and accompanied by fault water.The coupled effect of fault gouge and water significantly impacts the slip behavior of the fault,which may weaken the fault structure and further induce rupture propagation and earthquakes.In this study,we carried out a laboratory experiment to investigate the fluid-induced slip behavior of fault filled with gouge.The friction evolution characteristic associated with fluid pressure and effective stress was investigated during the slip process.In addition,the role transformation process of the gouge on the slip behavior of fault was revealed.The experimental result indicates that the friction on the filled fault surface is significantly affected by fault gouge.The rupture of the gouge promotes fault slip and the fluid pressure plays a vital role in the initiation of fault slip.The fault gouge enhances the shearing strength of the fault and acts as a barrier before the initial slip under fluid injection.Nevertheless,the fault gouge would accelerate the fault slip and transform into lubricant after the initial slip.展开更多
Carbonaceous materials in seismic fault zones may considerably influence seismic fault slip;however,the formation mechanism of carbonaceous materials remains unclear.In this study,we proposed a novel hypothesis for th...Carbonaceous materials in seismic fault zones may considerably influence seismic fault slip;however,the formation mechanism of carbonaceous materials remains unclear.In this study,we proposed a novel hypothesis for the formation of carbonaceous materials in fault gouge.Thus,we conducted a CO_(2) hydrogenation experiment in a high-temperature reactor at a co-seismic temperature,with fault gouge formed during the Wenchuan earthquake as the catalyst.Our experimental results demonstrate that carbonaceous materials in fault zones are formed on the fault gouge during the chemical reaction process,suggesting that the carbonaceous materials are possibly generated from the catalytic hydrogenation of CO_(2),followed by thermal cracking of its products.The results of this study provide a theoretical basis for understanding fault behavior and earthquake physics.展开更多
This paper investigates the frictional behavior of the infilled rock fracture under dynamic normal stress.A series of direct shear tests were conducted on saw-cut granite fractures infilled with quartz using a selfdev...This paper investigates the frictional behavior of the infilled rock fracture under dynamic normal stress.A series of direct shear tests were conducted on saw-cut granite fractures infilled with quartz using a selfdeveloped dynamic shear apparatus,and the effects of normal load oscillation amplitude,normal load oscillation period and sliding velocity were studied.The test results reveal that the shear response can be divided into three stages over a whole loading-unloading process,characterized by different time spans and stress variations.Generally,a smaller oscillation amplitude,a longer oscillation period and a fast shear velocity promote the stability of the friction system,which is also confirmed by the Coulomb failure criterion calculated based on the observed periodic apparent friction coefficient.The dynamic strengthening/weakening phenomenon is dependent on the oscillation amplitude and product of sliding velocity and oscillation period(vT).Also,the rate and state friction law incorporating the parameter a that characterizes the normal stress variation is employed to describe the dynamic friction coefficient but exhibits an incompetent performance when handling intensive variation in normal stress.Finally,the potential seismicity induced by oscillating normal stress based on the observed stress drop is analyzed.This work helps us understand the sliding process and stability evolution of natural faults,and its benefits for relative hazard mitigation.展开更多
This paper experimentally explores the frictional sliding behavior of two simulated gouges:one,a series of quartz–smectite mixtures,and the other,powdered natural rocks,aiming to evaluate and codify the effect of min...This paper experimentally explores the frictional sliding behavior of two simulated gouges:one,a series of quartz–smectite mixtures,and the other,powdered natural rocks,aiming to evaluate and codify the effect of mineralogy on gouge dilation and frictional strength,stability,and healing.Specifically,velocity-stepping and slide-hold-slide experiments were performed in a double direct shear configuration to analyze frictional constitutive parameters at room temperature,under normal stresses of 10,20,and 40 MPa.Gouge dilation was measured based on the applied step-wise changes in shear velocity.The frictional response of the quartz–smectite mixtures and powdered natural rocks are affected by their phyllosilicate content.Frictional strength and healing rates decrease with increasing phyllosilicate content,and at 20 wt.%a transition from velocity-weakening to velocity-strengthening behavior was noted.For both suites of gouges,dilation is positively correlated with frictional strength and healing rates,and negatively correlated with frictional stability.Changes in the permeability of gouge-filled faults were estimated from changes in mean porosity,indexed through measured magnitudes of gouge dilation.This combined analysis implies that the reactivation of caprock faults filled with phyllosilicaterich gouges may have a strong influence on permeability evolution in caprock faults.展开更多
Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar a...Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.展开更多
The frictional strength and sliding stability of faults are crucial in interpreting earthquake mechanisms and cycles.Herein,we report friction experiments on basalt fractures,using a self-designed triaxial apparatus t...The frictional strength and sliding stability of faults are crucial in interpreting earthquake mechanisms and cycles.Herein,we report friction experiments on basalt fractures,using a self-designed triaxial apparatus that allows direct shear of samples under coupled hydro-mechanical conditions.Velocitystepping(VS)and slide-hold-slide(SHS)experiments are performed on both bare and gouge-bearing surfaces of Xiashan basalt subjected to cyclic shear velocities at 1e30 mm/s,effective normal stresses of 1e5 MPa,and pore pressures of 70e300 kPa.The measured basalt friction coefficients are in the range of 0.67e0.74,which is sensitive to gouge thickness,normal stress,and water.Specifically,a reduction in friction coefficient is observed with an increment in gouge thickness,normal stress,and pore pressure.Based on the microscopic observation of the pre-and post-shearing sliding surfaces,this weakening effect in friction coefficient can be attributed to powder lubrication.Furthermore,the VS test results reveal predominantly velocity-strengthening behavior at investigated slip velocities,and this velocity strengthening behavior does not appear to be influenced by variations in normal stress,gouge thickness,and water.However,changes in sliding velocity and normal stress can lead to a shift between stable and unstable sliding.Specifically,stable sliding is favored by high sliding velocities and low normal stress applied in this study.Finally,we analyze the experimental data by calculating the rate-and-state parameters using the rate-and state-dependent friction(RSF)theory.Importantly,the calculated friction rate parameter(a-b)supports the velocity-strengthening behavior.Both frictional relaxation(Dmc)during hold periods and frictional healing(Dm)upon re-shearing are linearly proportional to the logarithmic hold time,which may be attributed to the growth in true contact area with hold time.This study sheds light on the roles of sliding velocity,and gouge thickness in controlling frictional strength and stability of basalt fractures.展开更多
Although friction characteristics of fault gouge are important to understand reactivation of fault,behavior of earthquake,and mechanism of slope failure,analysis results of fault gouge have low accuracy mostly than th...Although friction characteristics of fault gouge are important to understand reactivation of fault,behavior of earthquake,and mechanism of slope failure,analysis results of fault gouge have low accuracy mostly than those of soils or rocks due to its high heterogeneity and low strength.Therefore,to improve the accuracy of analysis results,we conducted simple regression analysis and structural equation model analysis and selected major influential factors of friction characteristics among many factors,and then we deduced advanced regression model with the highest coefficient of determination(R^(2)) via multiple regression analysis.Whereas most coefficients of determination in simple regression analysis are below0.3-0.4,coefficient of determination in multiple regression analysis is remarkably large as 0.657.展开更多
Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion w...Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion while extruding or grinding. The field investigation encompassed sample collecting from the Bailong River fault system of the western segment of the Qinling Orogenic Belt （QOB）; 44 samples of fault gouges were collected for quartz micro-morphology analysis. These samples were analyzed using field emission scanning electron microscopy. In addition, 14 samples were tested for thermo-luminescence dating. The results showed that most of the surface textures of quartz grains are characterized by fish scale, moss-like texture, and stalactite. However, a small amount of orange peel-like fractures and worm-hole-like shaped surface texture were observed. Moreover, a few typical conchoids or subconchoidal fractures in quartz grains can be seen. This implies that the Bailong River Fault was active repeatedly during the Quaternary period, but the main motion period is the Pleistocene. The 14 thermo-luminescence dating values showed two age groups： 343.29-184.06 ka and 92.18-13.87 ka. These study data reveal that fault movement started during the Pliocene, occurred frequently in the early-middle period of the Pleistocene, and the peak frequency of the motion was reached in the early Pleistocene. The fault motions were stopped terminated in the early Holocene. The results are significant for the natural disaster risk evaluation in the western segment of the QOB.展开更多
The role of authigenic clay growth in clay gouge is increasingly recognized as a key to understanding the mechanics of berittle faulting and fault zone processes,including creep and seismogenesis,and providing new ins...The role of authigenic clay growth in clay gouge is increasingly recognized as a key to understanding the mechanics of berittle faulting and fault zone processes,including creep and seismogenesis,and providing new insights into the ongoing debate about the frictional strength of brittle fault(Haines and van der Pluijm,2012).However,neither the conditions nor the processes which展开更多
In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock...In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge.展开更多
This paper presents a strategy to generate interference-free tool paths for machining sculptured surfaces. The strategy proposed here is first to determine the tool path topology. The values of the step length and the...This paper presents a strategy to generate interference-free tool paths for machining sculptured surfaces. The strategy proposed here is first to determine the tool path topology. The values of the step length and the path interval are then calculated based on the machining tolerance requirements. After detecting and eliminating the tool interference, the interference-free tool path is generated. The effectiveness of the developed algorithm is demonstrated through simulation and actual cutting tests.展开更多
Based on the principles of differential geometry,the basic equations are derived for generating gouging free tool path in 5-axis NC face milling,the influence of surface's local geometry is discussed,and the condi...Based on the principles of differential geometry,the basic equations are derived for generating gouging free tool path in 5-axis NC face milling,the influence of surface's local geometry is discussed,and the conditions of using cutter with reasonable diameter are presented.展开更多
K-Ar dating of synkinematic illite is increasingly recognized as a central method to constrain the timing of shallow crustal faulting.Methods of efficient sample preparation and quantitative identification of illite p...K-Ar dating of synkinematic illite is increasingly recognized as a central method to constrain the timing of shallow crustal faulting.Methods of efficient sample preparation and quantitative identification of illite polytypes are critical to acquiring K-Ar isotope data for authigenic clays.In this respect,we compared the commonly used clay size separation method through centrifugation with vacuum filtration technology,showing that the former is prone to extract fractions with finer particle sizes under similar conditions,thus improving the error in the authigenic end-member age.Additionally,we demonstrated that the side-packed mounting method for X-ray diffraction analysis can significantly enhance the randomness in powder samples,thus improving the quantification accuracy compared with the front-packed and back-packed methods.The validity of our quantification method was confirmed by comparing Profex■modeling patterns with a suite of synthetic mixtures of known compositions,yielding an average analytical error of 3%.Dating results of these artificial mixtures and the reference materials indicated that a large range in percentages of detrital illite and a sufficient amount of age data will produce reliable results for ages of both extrapolated end-members.However,if the range is limited,the extrapolated age close to those of datasets is still reliable.展开更多
A great deal of important information referring to fault motion (such as fault activities period, intensity, frequency, and even dynamic background, etc.) can be revealed by resolving fault gouge, which are the specia...A great deal of important information referring to fault motion (such as fault activities period, intensity, frequency, and even dynamic background, etc.) can be revealed by resolving fault gouge, which are the special result of fault motion while extruding or grinding. Based on the field investigation, collected from Bailongjiang fault system of Western Qinling Orogenic (QO) Belt, 44 samples of fault gouge were for quartz micro-morphology observation and statistics by the field emission SEM, and 14 samples were tested by thermo-luminescence dating. The results showed that most of the micro-morphology of quartz grains are fish scale and orange-haut fractures, but a small amount of moss-like, stalactitic, and subconchoidal fractures. Also very few decay of quartz grains and typical conchoids fracture quartz grains can be seen. This implied that the Bailongjiang fault system was motioned repeatedly in Quaternary period but main motion period was Pleistocene. 14 thermo-luminescence dating values showed herewith two groups as 343.29-184.06 ka and 92.18-13.87 ka. Therefore, the conclusions can be reached that the fault system were motioned starting at Pliocene epoch, frequently in the middle of Pleistocene (343.29-184.06 ka), and peak frequency in late Pleistocene (92.18-13.87 ka). The fault system motions have stopped at Holocene. The results are significant for the natural disaster risk evaluation in western QO region.展开更多
ESR dating has been widely used in seismic assessment. In this paper, we collected fault gouge samples systematically for ESR (Electron Spin Resonance) dating, and sediment samples of overlying strata, and offset stra...ESR dating has been widely used in seismic assessment. In this paper, we collected fault gouge samples systematically for ESR (Electron Spin Resonance) dating, and sediment samples of overlying strata, and offset strata for OSL (Optically Stimulated Luminescence) dating along Xiaoshan-Qiuchuan fault (XQF) trending NE-SW, Xiaofeng-Sanmen fault (XSF) trending NW-SE, and Changhua-Putuo fault (CPF) trending E-W. In the same fault outcrop, the ESR data of fault gouge is greater than the OSL data of the strata offset by fault. Therefore, the ESR data of fault gouge colleted in Hangzhou region do not represent the time of weak fault movement in Late Quaternary region, but represent the strong fault movements in Late Cenozoic. The episode of fault movement in Late Cenozoic could be speculated according to the ESR data: 1.000.58 Ma, there were strong fault movements along the XSF, XQF and CPF in Hangzhou region; 0.580.45 Ma, the fault movements of all faults became weaker and did not zero ESR signals significantly for ESR dating of fault movements; 0.450.20 Ma, there were strong fault movements along part of XQF; 0.10.01 Ma, there were fault movements along the XSF only, but the fault movements were not strong enough to reset the ESR signal; Since 0.01 Ma, the Hangzhou region tends to be stable. In addition, the XSF might be the division line of fault segmentation of XQF; there were strong fault movements along the southwest segment of XQF during 0.45 Ma to 0.20 Ma; while the fault movements along the northeast segment of XQF mainly occurred during 1.000.58 Ma.展开更多
How to find more effective way to stabilize the borehole wall in the fault gouge section is the key technical challenge to control the stability of the borehole wall in the Wenchuan fault gouge section during the proc...How to find more effective way to stabilize the borehole wall in the fault gouge section is the key technical challenge to control the stability of the borehole wall in the Wenchuan fault gouge section during the process of core drilling. Here we try to describe the characters of deep fault gouge in fracture zones from the undisturbed fault gouge samples which are obtained during the core drilling. The X- Ray Diffraction （XRD）, X-Ray Fluorescence （XRF） and Scanning Electron Microscope （SEM） provided the detailed information of the fault gouge＇s microscopic characteristics on the density, moisture content, expansibility, dispersity, permeability, tensile strength and other main physical-mechanical properties. Based on these systematic experimental studies above and analysis of the fault gouge instability mechanism, a new technical procedure to stabilize the borehole wall is proposed -- a low water and a low loss low permeability drilling fluid system that consists of 4% day ＋ 0.5% CMC-HV ＋ 2% S-1 ＋ 3%sulfonated asphalt ＋ 1% SMC ＋ 0.5% X-1 ＋ 0-5% T type lubricant ＋ barite for core drilling in fault gouge sections.展开更多
The process and result of fractal research of natural fault gouge collected from the active fault zone at northern edge of Western Qinling Mt. by using optical and electronic microscope technics were introduced in thi...The process and result of fractal research of natural fault gouge collected from the active fault zone at northern edge of Western Qinling Mt. by using optical and electronic microscope technics were introduced in this paper. The fractal dimension of this fault gouge is D =2.594±0.122 (2 D plane D =1.594±0.122), and its upper limit of fractal dimension occurs at grain size at 9.6～19.2 mm. The study result shows that this gouge is fractal, and its characteristic displacement parameter of stick slip friction can be determined by upper limit of fractal dimension. The feature of protolith which affect fractality and the significance of gouge fractal to seismic fault changes are also disscussed in the paper.展开更多
The relative age of fractures can be determined through structural analyses in the field or through the detailed mineralogical (XRD) and chemical analyses (AAS method, volumetric, and gravimetric analysis) of fault go...The relative age of fractures can be determined through structural analyses in the field or through the detailed mineralogical (XRD) and chemical analyses (AAS method, volumetric, and gravimetric analysis) of fault gouge in the laboratory. The aim of this work was to compare these approaches. It was hypothesised that the two methods would yield consistent results. The studied faults were located in the Rychleby Mts, part of the Sudetic Marginal Fault Zone. The relative age of the faults was determined in the field through the application of the intersection law. The fault gouges were sampled in a crystalline limestone quarry near the village of Vápenná. The mineralogical composition of the fault gouges has been established by XRD analysis of powder samples and analysis of preferentially oriented clay minerals. From our result, it is clear that these two approaches yielded consistent results with regard to the relative age of the faults.展开更多
文摘During the electromagnetic railgun launch process,high temperature and high current conditions can lead to armature wear,affecting armature/rail contact and degrading launch performance.This paper starts with the analysis of the metal liquid film formation at the armature/rail contact interface.1D and 3D models are developed based on the characteristic relational equation obtained from the melt liquid film model.These models incorporate thermodynamic equilibrium phase diagram,transient heat and mass transfer model,copper-aluminum alloy reaction model,nonlinear electrical conductivity relational equation and nonlinear thermal conductivity relational equation to analyze the temperature distribution and copper-aluminum intermetallic compounds(Cu-Al IMCs)formation in the melt liquid film.The wear mechanism and influence law of armature are explained in detail from different perspectives to un-derstand and predict the transition and gouging phenomena at the contact interface.The model's validity is confirmed by the results of electromagnetic launch experiments,providing insights for future structure design and material selection of the armature and rail.
基金supported by the research grant from Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2019-02)。
文摘Geochemistry of the fault gouge record information on fault behaviors and environmental conditions.We investigated variations in the mineralogical and geochemical compositions of the fault gouge sampled from the margin zone(MZ)to the slip central zone(CZ)of the fault gouge in the Beichuan-Yingxiu surface rupture zone of the Wenchuan Earthquake.Results show that the clay minerals contents increase from the MZ to CZ,and the quartz and plagioclase contents slight decrease.An increasing enrichment in Al_(2)O_(3),Fe_(2)O_(3),and K_(2)O are observed toward the CZ;the decomposition of quartz and plagioclase,as well as the depletion of Si O_(2),Ca O,Na_2O,and P_(2)O_(5)suggest that the alkaline-earth elements are carried away by the fluids.It can be explained that the stronger coseismic actions in the CZ allow more clay minerals to form,decompose quartz and plagioclase,and alter plagioclase to chlorite.The mass loss in the CZ is larger than that in MZ,which is maybe due to the more concentrated stress in the strongly deformed CZ,however other causes will not be excluded.
文摘Fault zones are usually filled with fault gouge and accompanied by fault water.The coupled effect of fault gouge and water significantly impacts the slip behavior of the fault,which may weaken the fault structure and further induce rupture propagation and earthquakes.In this study,we carried out a laboratory experiment to investigate the fluid-induced slip behavior of fault filled with gouge.The friction evolution characteristic associated with fluid pressure and effective stress was investigated during the slip process.In addition,the role transformation process of the gouge on the slip behavior of fault was revealed.The experimental result indicates that the friction on the filled fault surface is significantly affected by fault gouge.The rupture of the gouge promotes fault slip and the fluid pressure plays a vital role in the initiation of fault slip.The fault gouge enhances the shearing strength of the fault and acts as a barrier before the initial slip under fluid injection.Nevertheless,the fault gouge would accelerate the fault slip and transform into lubricant after the initial slip.
文摘Carbonaceous materials in seismic fault zones may considerably influence seismic fault slip;however,the formation mechanism of carbonaceous materials remains unclear.In this study,we proposed a novel hypothesis for the formation of carbonaceous materials in fault gouge.Thus,we conducted a CO_(2) hydrogenation experiment in a high-temperature reactor at a co-seismic temperature,with fault gouge formed during the Wenchuan earthquake as the catalyst.Our experimental results demonstrate that carbonaceous materials in fault zones are formed on the fault gouge during the chemical reaction process,suggesting that the carbonaceous materials are possibly generated from the catalytic hydrogenation of CO_(2),followed by thermal cracking of its products.The results of this study provide a theoretical basis for understanding fault behavior and earthquake physics.
基金the National Natural Science Foundation of China(Nos.51904359,51978677 and 52111530089)the Guangdong Provincial Department of Science and Technology(No.2019ZT08G090)+2 种基金the Enhanced National Key Basic Research Program(No.2019-JCJQ-ZD-352-00-04)the Science and Technology Program for Sustainable Development of Shenzhen(No.KCXFZ202002011008532)the Open Research Fund of the State Key Laboratory of Coal Resources and Safe Mining,CUMT(No.SKLCRSM20KF002).
文摘This paper investigates the frictional behavior of the infilled rock fracture under dynamic normal stress.A series of direct shear tests were conducted on saw-cut granite fractures infilled with quartz using a selfdeveloped dynamic shear apparatus,and the effects of normal load oscillation amplitude,normal load oscillation period and sliding velocity were studied.The test results reveal that the shear response can be divided into three stages over a whole loading-unloading process,characterized by different time spans and stress variations.Generally,a smaller oscillation amplitude,a longer oscillation period and a fast shear velocity promote the stability of the friction system,which is also confirmed by the Coulomb failure criterion calculated based on the observed periodic apparent friction coefficient.The dynamic strengthening/weakening phenomenon is dependent on the oscillation amplitude and product of sliding velocity and oscillation period(vT).Also,the rate and state friction law incorporating the parameter a that characterizes the normal stress variation is employed to describe the dynamic friction coefficient but exhibits an incompetent performance when handling intensive variation in normal stress.Finally,the potential seismicity induced by oscillating normal stress based on the observed stress drop is analyzed.This work helps us understand the sliding process and stability evolution of natural faults,and its benefits for relative hazard mitigation.
基金supported by the National Natural Science Foundation of China (Nos. 41672268 and 41772286)the Petro China Innovation Foundation (2018D-5007-0202)the US Department of Energy (DEFE0023354)
文摘This paper experimentally explores the frictional sliding behavior of two simulated gouges:one,a series of quartz–smectite mixtures,and the other,powdered natural rocks,aiming to evaluate and codify the effect of mineralogy on gouge dilation and frictional strength,stability,and healing.Specifically,velocity-stepping and slide-hold-slide experiments were performed in a double direct shear configuration to analyze frictional constitutive parameters at room temperature,under normal stresses of 10,20,and 40 MPa.Gouge dilation was measured based on the applied step-wise changes in shear velocity.The frictional response of the quartz–smectite mixtures and powdered natural rocks are affected by their phyllosilicate content.Frictional strength and healing rates decrease with increasing phyllosilicate content,and at 20 wt.%a transition from velocity-weakening to velocity-strengthening behavior was noted.For both suites of gouges,dilation is positively correlated with frictional strength and healing rates,and negatively correlated with frictional stability.Changes in the permeability of gouge-filled faults were estimated from changes in mean porosity,indexed through measured magnitudes of gouge dilation.This combined analysis implies that the reactivation of caprock faults filled with phyllosilicaterich gouges may have a strong influence on permeability evolution in caprock faults.
基金financially supported by the Vietnam National Foundation for Science and Technology Development(NAFOSTED) under grant number 105.032011.11 to Bui Hoang Bac
文摘Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.
基金funded by National Natural Science Foundation of China(Grant Nos.51509154 and 42077247)Natural Science Foundation of Zhejiang Province(Grant No.LGJ20E090001).
文摘The frictional strength and sliding stability of faults are crucial in interpreting earthquake mechanisms and cycles.Herein,we report friction experiments on basalt fractures,using a self-designed triaxial apparatus that allows direct shear of samples under coupled hydro-mechanical conditions.Velocitystepping(VS)and slide-hold-slide(SHS)experiments are performed on both bare and gouge-bearing surfaces of Xiashan basalt subjected to cyclic shear velocities at 1e30 mm/s,effective normal stresses of 1e5 MPa,and pore pressures of 70e300 kPa.The measured basalt friction coefficients are in the range of 0.67e0.74,which is sensitive to gouge thickness,normal stress,and water.Specifically,a reduction in friction coefficient is observed with an increment in gouge thickness,normal stress,and pore pressure.Based on the microscopic observation of the pre-and post-shearing sliding surfaces,this weakening effect in friction coefficient can be attributed to powder lubrication.Furthermore,the VS test results reveal predominantly velocity-strengthening behavior at investigated slip velocities,and this velocity strengthening behavior does not appear to be influenced by variations in normal stress,gouge thickness,and water.However,changes in sliding velocity and normal stress can lead to a shift between stable and unstable sliding.Specifically,stable sliding is favored by high sliding velocities and low normal stress applied in this study.Finally,we analyze the experimental data by calculating the rate-and-state parameters using the rate-and state-dependent friction(RSF)theory.Importantly,the calculated friction rate parameter(a-b)supports the velocity-strengthening behavior.Both frictional relaxation(Dmc)during hold periods and frictional healing(Dm)upon re-shearing are linearly proportional to the logarithmic hold time,which may be attributed to the growth in true contact area with hold time.This study sheds light on the roles of sliding velocity,and gouge thickness in controlling frictional strength and stability of basalt fractures.
基金supported by Postdoctoral Fellowship Program funded by the Ministry of Education of the Republic of Korea through the Chungbuk National University in 2020。
文摘Although friction characteristics of fault gouge are important to understand reactivation of fault,behavior of earthquake,and mechanism of slope failure,analysis results of fault gouge have low accuracy mostly than those of soils or rocks due to its high heterogeneity and low strength.Therefore,to improve the accuracy of analysis results,we conducted simple regression analysis and structural equation model analysis and selected major influential factors of friction characteristics among many factors,and then we deduced advanced regression model with the highest coefficient of determination(R^(2)) via multiple regression analysis.Whereas most coefficients of determination in simple regression analysis are below0.3-0.4,coefficient of determination in multiple regression analysis is remarkably large as 0.657.
基金granted by Geological Survey Project(Grant No.1212011120072)the Project of the National Key Technology R&D Program(Grant No.2011BAK12B09)the Project of the National Natural Science Foundation of China(Grant No.41072269)
文摘Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion while extruding or grinding. The field investigation encompassed sample collecting from the Bailong River fault system of the western segment of the Qinling Orogenic Belt （QOB）; 44 samples of fault gouges were collected for quartz micro-morphology analysis. These samples were analyzed using field emission scanning electron microscopy. In addition, 14 samples were tested for thermo-luminescence dating. The results showed that most of the surface textures of quartz grains are characterized by fish scale, moss-like texture, and stalactite. However, a small amount of orange peel-like fractures and worm-hole-like shaped surface texture were observed. Moreover, a few typical conchoids or subconchoidal fractures in quartz grains can be seen. This implies that the Bailong River Fault was active repeatedly during the Quaternary period, but the main motion period is the Pleistocene. The 14 thermo-luminescence dating values showed two age groups： 343.29-184.06 ka and 92.18-13.87 ka. These study data reveal that fault movement started during the Pliocene, occurred frequently in the early-middle period of the Pleistocene, and the peak frequency of the motion was reached in the early Pleistocene. The fault motions were stopped terminated in the early Holocene. The results are significant for the natural disaster risk evaluation in the western segment of the QOB.
基金financed by the National Youth Sciences Foundation of China (No. 41502044)
文摘The role of authigenic clay growth in clay gouge is increasingly recognized as a key to understanding the mechanics of berittle faulting and fault zone processes,including creep and seismogenesis,and providing new insights into the ongoing debate about the frictional strength of brittle fault(Haines and van der Pluijm,2012).However,neither the conditions nor the processes which
文摘In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge.
文摘This paper presents a strategy to generate interference-free tool paths for machining sculptured surfaces. The strategy proposed here is first to determine the tool path topology. The values of the step length and the path interval are then calculated based on the machining tolerance requirements. After detecting and eliminating the tool interference, the interference-free tool path is generated. The effectiveness of the developed algorithm is demonstrated through simulation and actual cutting tests.
文摘Based on the principles of differential geometry,the basic equations are derived for generating gouging free tool path in 5-axis NC face milling,the influence of surface's local geometry is discussed,and the conditions of using cutter with reasonable diameter are presented.
基金funded by the National Natural Science Foundation of China(Nos.42072240 and 41602218)Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(No.GML2019ZD0201)the Fund from the Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Chinese Academy of Geological Sciences(Nos.J1901-30 and J1908)。
文摘K-Ar dating of synkinematic illite is increasingly recognized as a central method to constrain the timing of shallow crustal faulting.Methods of efficient sample preparation and quantitative identification of illite polytypes are critical to acquiring K-Ar isotope data for authigenic clays.In this respect,we compared the commonly used clay size separation method through centrifugation with vacuum filtration technology,showing that the former is prone to extract fractions with finer particle sizes under similar conditions,thus improving the error in the authigenic end-member age.Additionally,we demonstrated that the side-packed mounting method for X-ray diffraction analysis can significantly enhance the randomness in powder samples,thus improving the quantification accuracy compared with the front-packed and back-packed methods.The validity of our quantification method was confirmed by comparing Profex■modeling patterns with a suite of synthetic mixtures of known compositions,yielding an average analytical error of 3%.Dating results of these artificial mixtures and the reference materials indicated that a large range in percentages of detrital illite and a sufficient amount of age data will produce reliable results for ages of both extrapolated end-members.However,if the range is limited,the extrapolated age close to those of datasets is still reliable.
文摘A great deal of important information referring to fault motion (such as fault activities period, intensity, frequency, and even dynamic background, etc.) can be revealed by resolving fault gouge, which are the special result of fault motion while extruding or grinding. Based on the field investigation, collected from Bailongjiang fault system of Western Qinling Orogenic (QO) Belt, 44 samples of fault gouge were for quartz micro-morphology observation and statistics by the field emission SEM, and 14 samples were tested by thermo-luminescence dating. The results showed that most of the micro-morphology of quartz grains are fish scale and orange-haut fractures, but a small amount of moss-like, stalactitic, and subconchoidal fractures. Also very few decay of quartz grains and typical conchoids fracture quartz grains can be seen. This implied that the Bailongjiang fault system was motioned repeatedly in Quaternary period but main motion period was Pleistocene. 14 thermo-luminescence dating values showed herewith two groups as 343.29-184.06 ka and 92.18-13.87 ka. Therefore, the conclusions can be reached that the fault system were motioned starting at Pliocene epoch, frequently in the middle of Pleistocene (343.29-184.06 ka), and peak frequency in late Pleistocene (92.18-13.87 ka). The fault system motions have stopped at Holocene. The results are significant for the natural disaster risk evaluation in western QO region.
基金Project of the Tenth Five-year Plan of Hangzhou Goverment and Earthquake Administration of Hangzhou (HZZFCG-2005-A4)
文摘ESR dating has been widely used in seismic assessment. In this paper, we collected fault gouge samples systematically for ESR (Electron Spin Resonance) dating, and sediment samples of overlying strata, and offset strata for OSL (Optically Stimulated Luminescence) dating along Xiaoshan-Qiuchuan fault (XQF) trending NE-SW, Xiaofeng-Sanmen fault (XSF) trending NW-SE, and Changhua-Putuo fault (CPF) trending E-W. In the same fault outcrop, the ESR data of fault gouge is greater than the OSL data of the strata offset by fault. Therefore, the ESR data of fault gouge colleted in Hangzhou region do not represent the time of weak fault movement in Late Quaternary region, but represent the strong fault movements in Late Cenozoic. The episode of fault movement in Late Cenozoic could be speculated according to the ESR data: 1.000.58 Ma, there were strong fault movements along the XSF, XQF and CPF in Hangzhou region; 0.580.45 Ma, the fault movements of all faults became weaker and did not zero ESR signals significantly for ESR dating of fault movements; 0.450.20 Ma, there were strong fault movements along part of XQF; 0.10.01 Ma, there were fault movements along the XSF only, but the fault movements were not strong enough to reset the ESR signal; Since 0.01 Ma, the Hangzhou region tends to be stable. In addition, the XSF might be the division line of fault segmentation of XQF; there were strong fault movements along the southwest segment of XQF during 0.45 Ma to 0.20 Ma; while the fault movements along the northeast segment of XQF mainly occurred during 1.000.58 Ma.
基金supported by the Land&Resources Ministry of China,the China Geological Survey and the research institute of prospecting technology in the Chinese Academy of Geological Sciences,sincere thanks heresupported by National Natural Science Foundation of China(Grant Nos.41272331,51204027)the State Key Laboratory of Geohazard Prevention&Geoenvironment Protection(Grant Nos.SKLGP2012Z007,SKLGP2014Z001,SKLGP2015Z010)
文摘How to find more effective way to stabilize the borehole wall in the fault gouge section is the key technical challenge to control the stability of the borehole wall in the Wenchuan fault gouge section during the process of core drilling. Here we try to describe the characters of deep fault gouge in fracture zones from the undisturbed fault gouge samples which are obtained during the core drilling. The X- Ray Diffraction （XRD）, X-Ray Fluorescence （XRF） and Scanning Electron Microscope （SEM） provided the detailed information of the fault gouge＇s microscopic characteristics on the density, moisture content, expansibility, dispersity, permeability, tensile strength and other main physical-mechanical properties. Based on these systematic experimental studies above and analysis of the fault gouge instability mechanism, a new technical procedure to stabilize the borehole wall is proposed -- a low water and a low loss low permeability drilling fluid system that consists of 4% day ＋ 0.5% CMC-HV ＋ 2% S-1 ＋ 3%sulfonated asphalt ＋ 1% SMC ＋ 0.5% X-1 ＋ 0-5% T type lubricant ＋ barite for core drilling in fault gouge sections.
文摘The process and result of fractal research of natural fault gouge collected from the active fault zone at northern edge of Western Qinling Mt. by using optical and electronic microscope technics were introduced in this paper. The fractal dimension of this fault gouge is D =2.594±0.122 (2 D plane D =1.594±0.122), and its upper limit of fractal dimension occurs at grain size at 9.6～19.2 mm. The study result shows that this gouge is fractal, and its characteristic displacement parameter of stick slip friction can be determined by upper limit of fractal dimension. The feature of protolith which affect fractality and the significance of gouge fractal to seismic fault changes are also disscussed in the paper.
文摘The relative age of fractures can be determined through structural analyses in the field or through the detailed mineralogical (XRD) and chemical analyses (AAS method, volumetric, and gravimetric analysis) of fault gouge in the laboratory. The aim of this work was to compare these approaches. It was hypothesised that the two methods would yield consistent results. The studied faults were located in the Rychleby Mts, part of the Sudetic Marginal Fault Zone. The relative age of the faults was determined in the field through the application of the intersection law. The fault gouges were sampled in a crystalline limestone quarry near the village of Vápenná. The mineralogical composition of the fault gouges has been established by XRD analysis of powder samples and analysis of preferentially oriented clay minerals. From our result, it is clear that these two approaches yielded consistent results with regard to the relative age of the faults.
