A two-dimensional finite element method （FEM） model that incorporates faults, elastic rock physical properties, topographical load due to gravity and far-field plate velocity boundary conditions was used to recogniz...A two-dimensional finite element method （FEM） model that incorporates faults, elastic rock physical properties, topographical load due to gravity and far-field plate velocity boundary conditions was used to recognize the seismogenic stress state along the fold-and-thrust belt of the Precordillera-Sierras Pampeanas ranges of western Argentina. A plane strain model with nine experiments was presented here to examine the fault strength with two major rock phyical properties： cohesion and angle of internal friction. Mohr-Coulomb failure criterion with bulk rock properties were applied to analyse faults. The stress field at any point of the model was assumed to be comprised of gravitational and tectonic components. The analysis was focused to recognize the seismogenic shear strain concentrated in the internal-cristaline domain of the orogene shown by the modeling. Modeling results are presented in terms of four parameters, i. e., （i） distributions, orientations, and magnitudes of principal stresses （σ1 and σ3）, （ii） displacement vector1 （iii） strain distribution, and （iv） maximum shear stress （τmax） contour line within the model. The simulation results show that the compressive stress is distributed in and around the fault systems. The overall orientation of of σ1 is in horizontal directions, although reorientations do occur within some stress weaker parts, especially subsequent to the faults. A large-scale shear stress is accumulating along the active faults of Tapias-Villicum Fault （TVF）, Salinas-Berros Fault （SBF）, Ampacama-Niquizanga Fault （ANF） and Las Charas Fault （CF）, which could act as local stress and strain modulators to localize the earthquakesoccurrence.展开更多
The hazards of fault reactivation caused by fluid injection are a growing concern.However,traditional evaluation methods of fault stability are likely to underestimate the risk in fault segments with a high clay conte...The hazards of fault reactivation caused by fluid injection are a growing concern.However,traditional evaluation methods of fault stability are likely to underestimate the risk in fault segments with a high clay content.Therefore,an extended evaluation method of fault stability(ECPP)incorporating the heterogeneity in friction strength caused by variation in the clay content within the fault zone is established in this study.After characterizing the current stress field of the BZ34-2 Oilfield in the Huanghekou Sag,Bohai Bay Basin,the reactivation potential of faults is evaluated using both traditional and ECPP methods.Traditional evaluation of fault stability shows that all faults are stable in the present stress field.Faults oriented ENE have a relatively high risk.The maximum sustainable fluid pressure Δp is approximately 8.8-8.9 MPa and 9.3-9.9 MPa.When considering the heterogeneity in fault friction strength,the fault stability is clearly controlled by the clay content of the faults.The high-risk fault segments assessed using traditional methods are no longer obvious,which reflects the importance of incorporating friction strength heterogeneity in the process of fault evaluation.Moreover,the results also show that most fault segments are activated when the fault zone is dominated by montmorillonite,reflecting the strong influence of clay mineral types on fault stability.The factors influencing the heterogeneity of fault friction strength are very complicated in actual situations.Therefore,future work should focus on establishing a database through a large number of experiments and investigating the relationship between the friction coefficient and the main controlling factors.展开更多
We analyze the influences of interstitial atoms on the generalized stacking fault energy （GSFE）, strength, and ductility of Ni by first-principles calculations. Surface energies and GSFE curves are calculated for t...We analyze the influences of interstitial atoms on the generalized stacking fault energy （GSFE）, strength, and ductility of Ni by first-principles calculations. Surface energies and GSFE curves are calculated for the （112） （111） and / 101） （ 1 1 1） systems. Because of the anisotropy of the single crystal, the addition of interstitials tends to promote the strength of Ni by slipping along the （10T） direction while facilitating plastic deformation by slipping along the （115） direction. There is a different impact on the mechanical behavior of Ni when the interstitials are located in the slip plane. The evaluation of the Rice criterion reveals that the addition of the interstitials H and O increases the brittleness in Ni and promotes the probability of cleavage fracture, while the addition of S and N tends to increase the ductility. Besides, P, H, and S have a negligible effect on the deformation tendency in Ni, while the tendency of partial dislocation is more prominent with the addition of N and O. The addition of interstitial atoms tends to increase the high-energy barrier γmax, thereby the second partial resulting from the dislocation tends to reside and move on to the next layer.展开更多
In this paper a two dimensional (2 D) model of earthquake fault rupturing was presented. It was estabilished on the basis of 1 D spring block model. Using this model, we studied the dynamical plane strain fractur...In this paper a two dimensional (2 D) model of earthquake fault rupturing was presented. It was estabilished on the basis of 1 D spring block model. Using this model, we studied the dynamical plane strain fracture problem, modeled the whole dynamical process of nucleating, expanding and propagating of fracture on a 2 D fault with homogeneous or inhomogeneous rupture strength distribution. Our studies show that under homogeneous prestress condition, the fault will gain enough momentum to tear strong obstacles in their propagating path. The rupturing fronts can also propagate forth around the isolated barriers. It is shown that the stopping conditions for rupturing processes play an important role in modeling whole earthquake process. We also studied the dynamical rupturing problems of the fault on which the rupture strength distribution is inhomogeneous, and modeled the earthquake sequence generated on a 2 D fault with the strength distribution of fractal structure. It possesses some similar features as a seismic sequence in the nature. These features mainly depend on the distribution of rupture strength on the fault plane and the level of initial stress drop. The modeling studies which were established on the basis of experiments and observations provided the physical basis for explaining some statistical rules of seismicity.展开更多
To estimate the near-fault inelastic response spectra, the accuracy of six existing strength reduction factors （R） proposed by different investigators were evaluated by using a suite of near-fault earthquake records...To estimate the near-fault inelastic response spectra, the accuracy of six existing strength reduction factors （R） proposed by different investigators were evaluated by using a suite of near-fault earthquake records with directivity-induced pulses. In the evaluation, the force-deformation relationship is modelled by elastic-perfectly plastic, bilinear and stiffness degrading models, and two site conditions, rock and soil, are considered. The R-value ratio （ratio of the R value obtained from the existing R-expressions （or the R-p-T relationships） to that from inelastic analyses） is used as a measurement parameter. Results show that the R-expressions proposed by Ordaz ＆ Perez-Rocha are the most suitable for near-fault ground motions, followed by the Newmark ＆ Hall and the Berrill et al. relationships. Based on an analysis using the near-fault ground motion dataset, new expressions of R that consider the effects of site conditions are presented and verified.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
Although the Indus-Tsangpo Suture(ITS) is the most spectacular thrust system of continent-continent collision in the world, fundamental questions about its strength evolution and deformation behavior transition remain...Although the Indus-Tsangpo Suture(ITS) is the most spectacular thrust system of continent-continent collision in the world, fundamental questions about its strength evolution and deformation behavior transition remain unanswered. Here we reported, for the first time, frictional melting-induced pseudotachylytes in the intensively deformed felsic rocks along the ITS zone in southern Tibet. This study reveals that pseudotachylytes induced profound weakness of the boundary fault between Indian and Asian plates. The intrinsically low strength of the foliated microlites crystallized from frictional melt or glass(i.e., pseudotachylyte) at seismogenic depths compared with the surrounding coarse-grained quartzofeldspathic rocks in the brittle and semi-brittle regime is sufficient to explain the localization of shear strain, the development of ductile shear zones embedded in strong wall rocks, and the transition from the strong to weak fault behaviors without invoking the presence of high fluid pressure or low friction coefficient metasomatic materials(e.g., smectite or lizardite) within the faults.展开更多
Computational complexity of complex system multiple fault diagnosis is a puzzle at all times. Based on the well known Mozetic＇s approach, a novel hierarchical model-based diagnosis methodology is put forward for impr...Computational complexity of complex system multiple fault diagnosis is a puzzle at all times. Based on the well known Mozetic＇s approach, a novel hierarchical model-based diagnosis methodology is put forward for improving efficency of multi-fault recognition and localization. Structural abstraction and weighted fault propagation graphs are combined to build diagnosis model. The graphs have weighted arcs with fault propagation probabilities and propagation strength. For solving the problem of coupled faults, two diagnosis strategies are used： one is the Lagrangian relaxation and the primal heuristic algorithms; another is the method of propagation strength. Finally, an applied example shows the applicability of the approach and experimental results are given to show the superiority of the presented technique.展开更多
Fe-Cr-Mn(W, V) austenite steels used as low radioactive structural materialsin fusion reactor have been investigated. The results show that the high temperature strength andthe creep fracture life of Fe-Cr-Mn(W, V) st...Fe-Cr-Mn(W, V) austenite steels used as low radioactive structural materialsin fusion reactor have been investigated. The results show that the high temperature strength andthe creep fracture life of Fe-Cr-Mn(W, V) steels can be effectively improved through (C+N)complex-strengthening, so can be the high temperature ductility. The strength and ductility of thesteels are superior to that of SUS316 steels and JPCAS below 673 K. The relationship betweenstrength, ductility and the formation temperature is related to the evolution of deformationmicrostructure. The fracture and microstructure observation above 673 K indicates that the main wayto further improve ductility at high temperature is the control of carbide coarsening at the grainboundaries.展开更多
基金the Ministry of Education, Culture, Sports, Science and Technology (Monbukagakusho) of Japan for its financial support of this research.
文摘A two-dimensional finite element method （FEM） model that incorporates faults, elastic rock physical properties, topographical load due to gravity and far-field plate velocity boundary conditions was used to recognize the seismogenic stress state along the fold-and-thrust belt of the Precordillera-Sierras Pampeanas ranges of western Argentina. A plane strain model with nine experiments was presented here to examine the fault strength with two major rock phyical properties： cohesion and angle of internal friction. Mohr-Coulomb failure criterion with bulk rock properties were applied to analyse faults. The stress field at any point of the model was assumed to be comprised of gravitational and tectonic components. The analysis was focused to recognize the seismogenic shear strain concentrated in the internal-cristaline domain of the orogene shown by the modeling. Modeling results are presented in terms of four parameters, i. e., （i） distributions, orientations, and magnitudes of principal stresses （σ1 and σ3）, （ii） displacement vector1 （iii） strain distribution, and （iv） maximum shear stress （τmax） contour line within the model. The simulation results show that the compressive stress is distributed in and around the fault systems. The overall orientation of of σ1 is in horizontal directions, although reorientations do occur within some stress weaker parts, especially subsequent to the faults. A large-scale shear stress is accumulating along the active faults of Tapias-Villicum Fault （TVF）, Salinas-Berros Fault （SBF）, Ampacama-Niquizanga Fault （ANF） and Las Charas Fault （CF）, which could act as local stress and strain modulators to localize the earthquakesoccurrence.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.42002152 and U20A2093)National Key Research and Development Program of China(Grant No.2022YFE0206800).
文摘The hazards of fault reactivation caused by fluid injection are a growing concern.However,traditional evaluation methods of fault stability are likely to underestimate the risk in fault segments with a high clay content.Therefore,an extended evaluation method of fault stability(ECPP)incorporating the heterogeneity in friction strength caused by variation in the clay content within the fault zone is established in this study.After characterizing the current stress field of the BZ34-2 Oilfield in the Huanghekou Sag,Bohai Bay Basin,the reactivation potential of faults is evaluated using both traditional and ECPP methods.Traditional evaluation of fault stability shows that all faults are stable in the present stress field.Faults oriented ENE have a relatively high risk.The maximum sustainable fluid pressure Δp is approximately 8.8-8.9 MPa and 9.3-9.9 MPa.When considering the heterogeneity in fault friction strength,the fault stability is clearly controlled by the clay content of the faults.The high-risk fault segments assessed using traditional methods are no longer obvious,which reflects the importance of incorporating friction strength heterogeneity in the process of fault evaluation.Moreover,the results also show that most fault segments are activated when the fault zone is dominated by montmorillonite,reflecting the strong influence of clay mineral types on fault stability.The factors influencing the heterogeneity of fault friction strength are very complicated in actual situations.Therefore,future work should focus on establishing a database through a large number of experiments and investigating the relationship between the friction coefficient and the main controlling factors.
基金supported by the National Natural Science Foundation of China(Grant No 51371123)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.2013140211003)+1 种基金the Natural Science Foundation of Shanxi Science Technological Commission,China(Grant No.2014011002)the Scientific and Technological Research Program of Chongqing Municipal Education Commission,China(Grant No.KJ131315)
文摘We analyze the influences of interstitial atoms on the generalized stacking fault energy （GSFE）, strength, and ductility of Ni by first-principles calculations. Surface energies and GSFE curves are calculated for the （112） （111） and / 101） （ 1 1 1） systems. Because of the anisotropy of the single crystal, the addition of interstitials tends to promote the strength of Ni by slipping along the （10T） direction while facilitating plastic deformation by slipping along the （115） direction. There is a different impact on the mechanical behavior of Ni when the interstitials are located in the slip plane. The evaluation of the Rice criterion reveals that the addition of the interstitials H and O increases the brittleness in Ni and promotes the probability of cleavage fracture, while the addition of S and N tends to increase the ductility. Besides, P, H, and S have a negligible effect on the deformation tendency in Ni, while the tendency of partial dislocation is more prominent with the addition of N and O. The addition of interstitial atoms tends to increase the high-energy barrier γmax, thereby the second partial resulting from the dislocation tends to reside and move on to the next layer.
文摘In this paper a two dimensional (2 D) model of earthquake fault rupturing was presented. It was estabilished on the basis of 1 D spring block model. Using this model, we studied the dynamical plane strain fracture problem, modeled the whole dynamical process of nucleating, expanding and propagating of fracture on a 2 D fault with homogeneous or inhomogeneous rupture strength distribution. Our studies show that under homogeneous prestress condition, the fault will gain enough momentum to tear strong obstacles in their propagating path. The rupturing fronts can also propagate forth around the isolated barriers. It is shown that the stopping conditions for rupturing processes play an important role in modeling whole earthquake process. We also studied the dynamical rupturing problems of the fault on which the rupture strength distribution is inhomogeneous, and modeled the earthquake sequence generated on a 2 D fault with the strength distribution of fractal structure. It possesses some similar features as a seismic sequence in the nature. These features mainly depend on the distribution of rupture strength on the fault plane and the level of initial stress drop. The modeling studies which were established on the basis of experiments and observations provided the physical basis for explaining some statistical rules of seismicity.
基金Foundation for Research and Science and Technology of New Zealand, Contract Number: C05X0208 and C05X0301the Foundation for Western Transportation Science and Technology Research, Contract No. 200831800098
文摘To estimate the near-fault inelastic response spectra, the accuracy of six existing strength reduction factors （R） proposed by different investigators were evaluated by using a suite of near-fault earthquake records with directivity-induced pulses. In the evaluation, the force-deformation relationship is modelled by elastic-perfectly plastic, bilinear and stiffness degrading models, and two site conditions, rock and soil, are considered. The R-value ratio （ratio of the R value obtained from the existing R-expressions （or the R-p-T relationships） to that from inelastic analyses） is used as a measurement parameter. Results show that the R-expressions proposed by Ordaz ＆ Perez-Rocha are the most suitable for near-fault ground motions, followed by the Newmark ＆ Hall and the Berrill et al. relationships. Based on an analysis using the near-fault ground motion dataset, new expressions of R that consider the effects of site conditions are presented and verified.
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supported by the National Natural Science Foundation of China(No.40921001 and No.40921001)the Geological Survey of China(No.1212010818094)to Xuthe Natural Sciences and Engineering Research Council of Canada to Ji
文摘Although the Indus-Tsangpo Suture(ITS) is the most spectacular thrust system of continent-continent collision in the world, fundamental questions about its strength evolution and deformation behavior transition remain unanswered. Here we reported, for the first time, frictional melting-induced pseudotachylytes in the intensively deformed felsic rocks along the ITS zone in southern Tibet. This study reveals that pseudotachylytes induced profound weakness of the boundary fault between Indian and Asian plates. The intrinsically low strength of the foliated microlites crystallized from frictional melt or glass(i.e., pseudotachylyte) at seismogenic depths compared with the surrounding coarse-grained quartzofeldspathic rocks in the brittle and semi-brittle regime is sufficient to explain the localization of shear strain, the development of ductile shear zones embedded in strong wall rocks, and the transition from the strong to weak fault behaviors without invoking the presence of high fluid pressure or low friction coefficient metasomatic materials(e.g., smectite or lizardite) within the faults.
文摘Computational complexity of complex system multiple fault diagnosis is a puzzle at all times. Based on the well known Mozetic＇s approach, a novel hierarchical model-based diagnosis methodology is put forward for improving efficency of multi-fault recognition and localization. Structural abstraction and weighted fault propagation graphs are combined to build diagnosis model. The graphs have weighted arcs with fault propagation probabilities and propagation strength. For solving the problem of coupled faults, two diagnosis strategies are used： one is the Lagrangian relaxation and the primal heuristic algorithms; another is the method of propagation strength. Finally, an applied example shows the applicability of the approach and experimental results are given to show the superiority of the presented technique.
文摘Fe-Cr-Mn(W, V) austenite steels used as low radioactive structural materialsin fusion reactor have been investigated. The results show that the high temperature strength andthe creep fracture life of Fe-Cr-Mn(W, V) steels can be effectively improved through (C+N)complex-strengthening, so can be the high temperature ductility. The strength and ductility of thesteels are superior to that of SUS316 steels and JPCAS below 673 K. The relationship betweenstrength, ductility and the formation temperature is related to the evolution of deformationmicrostructure. The fracture and microstructure observation above 673 K indicates that the main wayto further improve ductility at high temperature is the control of carbide coarsening at the grainboundaries.
