To elucidate the influence of confining pressure on microcrack evolution and macroscopic failure mechanisms in granite,a multi-perspective approach was adopted.This approach combined triaxial compression tests,acousti...To elucidate the influence of confining pressure on microcrack evolution and macroscopic failure mechanisms in granite,a multi-perspective approach was adopted.This approach combined triaxial compression tests,acoustic emission(AE)monitoring,and PFC simulations.The results show that:1)Confining pressure exhibits a pronounced linear correlation with both yield strength and compressive strength.The enhancement of confining pressure significantly improves the deformability of granite and promotes a progressive shift in failure mechanism from brittle rupture to ductile deformation;2)Increasing confining pressure elevates the stress threshold for microcrack initiation and suppresses crack propagation.As a result,the proportion of shear cracks increases(based on AE analysis)from 18.71%to 61.2%,marking a transition in the dominant failure mode from tensile to shear;3)Confining pressure facilitates the development of grain boundary shear cracks(GBSCs),establishing the primary damage pathways.In addition,local stress concentrations under high confinement conditions trigger intragranular cracking.This highlights the regulatory effect of confining pressure on microcrack evolution.展开更多
The stability of slopes and tunnels is controlled by rock discontinuities,and the rock discontinuities roughness and the sliding direction play a signifcant role in shear failure.However,three-dimensional roughness ev...The stability of slopes and tunnels is controlled by rock discontinuities,and the rock discontinuities roughness and the sliding direction play a signifcant role in shear failure.However,three-dimensional roughness evaluation considering shear directions is scare,and the internal shear fracturing processes,micromechanical mechanisms and failure precursor of rock discontinuities are not well understood.Therefore,this study proposes a novel roughness evaluation index to quantitatively analyze the anisotropic characteristics of rock discontinuities.In conjunction with shear tests,a novel 3D-GBM modelling method considering the micromineral constituent and particle size distribution characteristics of granite as well as the geometric shape of discontinuities was realized.The strength,macro and micro-fracture characteristics,visual anisotropic shear evolution process and microfailure mechanism of granite discontinuities at diferent roughness and shear direction were investigated.Finally,the spatial and temporal evolutions of AE parameter b-value and magnitude M were further analyzed to reveal the shear fracture precursor of granite discontinuities.展开更多
Microbially induced calcium carbonate precipitation(MICP)technology can induce calcium carbonate crystals with cementation and stable performance in the process of microbial metabolism or enzymization through the regu...Microbially induced calcium carbonate precipitation(MICP)technology can induce calcium carbonate crystals with cementation and stable performance in the process of microbial metabolism or enzymization through the regulation of environmental factors MICP can be used as a cementing agent to cement cohesionless sand particles to form the materials with the characteristics of higher strength,better durability and environmental friendli-ness,as well as a good engineering application prospect.In this paper,the shear strength of sand column was tested by triaxial compression tests,and the strength index was obtained.In order to further study the micro-strength mechanism and the failure process,based on the discrete element method,a numerical model of MICP cemented sand column was established considering the factors of matrix soil particle gradation,particle mor-phology,content ratio of induced calcium carbonate,pore distribution characteristics,inter-particle cementation and so on.The failure process of MICP cemented sand column under load was analysed by numerical simulation,and the reliability of the numerical model was tested by combining with the stress intensity curve of samples under test conditions.The results indicate that compared with the actual triaxial tests of MICP cemented sand column,although there are deviations in stress and strain,cohesion and internal friction angle,the numerical simulation shows similar development law and intensity amplitude,and the same failure trend.The work in this paper verifies the reliability of the numerical model and provides a theoretical basis for the subsequent analysis of the factors influencing the geotechnical mechanical properties of biomineralized materials.展开更多
In order to investigate the failure process of brittle rock under triaxial compression through both experimental and numerical approaches, the particle simulation method was used in numerical simulations and the simul...In order to investigate the failure process of brittle rock under triaxial compression through both experimental and numerical approaches, the particle simulation method was used in numerical simulations and the simulated results were compared with those of the experiment. The numerical simulation results, such as fracture propagation, microcrack distribution, stress-strain response, and damage patterns, were discussed in detail. The simulated results under various confining pressures （0-60 MPa） are in good agreement with the experimental results. The simulated results reveal that rock failure is caused by axial splitting under uniaxial compression. As the confining pressure increases, rock failure occurs in a few localized shear planes and the rock mechanical behavior is changed from brittle to ductile. Consequently, the peak failure strength, microcrack numbers, and the shear plane angle increase, but the ratio of tensile to shear microcracks decreases. The damage formation during the compression simulations indicates that the particle simulation method can produce similar behaviors as those observed through laboratory compression tests.展开更多
Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting.The stability of the surrounding rock is po...Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting.The stability of the surrounding rock is poor,and it is difficult to control.In this paper,a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber group under different dynamic loads.The results showed that under dynamic loading,the vertical stress of the surrounding rock of the chamber group increased in an oscillatory form.The maximum stress concentration coefficient reached 4.09.The damage degree of the roof was greater than that of the two sides.The deformation of the roof was approximately 1.2 times that of the two sides.For the chamber closer to the power source,the stress oscillation amplitude of the surrounding rock was larger,and the failure was more serious.The force of the anchorage structure showed a phased increasing characteristic;additionally,the force of the anchorage structure on the adjacent side of the chambers was greater than that on the other side.This study reveals the deformation and failure evolution laws of the surrounding rock of large section chamber groups under dynamic loading.展开更多
This paper focuses on the research of a semi-submersible platform equipped with a DP-assisted mooring system. Based on the working principles of the DP-assisted mooring system and the model of the platform motion, a t...This paper focuses on the research of a semi-submersible platform equipped with a DP-assisted mooring system. Based on the working principles of the DP-assisted mooring system and the model of the platform motion, a time domain simulation program is applied to analyze the impact, in the case of one line failure, on the platform motion, power consumption of the thrusters and the tension of the mooring lines. The results show that, under the 10-year wind dominant, a one line failure will have little impact on the tension of the mooring lines. When the failure line is windward, the power consumption will increase greatly with a weakened position of accuracy. However when the failure line is leeward, the power consumption will be reduced with a partly strengthened oosition of accuracy.展开更多
Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured ...Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured zone in the roadway.This will provide the basis numerical simulation to calculate the surrounding rock fractured zone in a roadway.Using the single factor and multi-factor orthogonal test method,the evolution law of roadway surrounding rock displacements,plastic zone and stress distribution under different conditions is studied.It reveals the roadway surrounding rock burst evolution process,and obtains five kinds of failure modes in deep soft rock roadway.Using the fuzzy mathematics clustering analysis method,the deep soft surrounding rock failure model in Zhujixi mine can be classified and patterns recognized.Compared to the identification results and the results detected by geological radar of surrounding rock loose circle,the reliability of the results of the pattern recognition is verified and lays the foundations for the support design of deep soft rock roadways.展开更多
Rainfall is one of the most important factors contributing to landslides, and gentle bedding incline, high-rainfall induced landslides are common throughout the world. Field observations and theoretical analyses have ...Rainfall is one of the most important factors contributing to landslides, and gentle bedding incline, high-rainfall induced landslides are common throughout the world. Field observations and theoretical analyses have been used to assess slope instability caused by permeability variation. In this study, the influence of rainfall infiltration on gentle bedding incline slope behaviour was investigated using a centrifuge physical simulation test. The magnitude, pattern and development of pore water and earth pressure at the interface;the shear failure surface features;and the corresponding deformation and failure processes were considered. A model with interbedded sand and mud was created, and a centrifuge was used to simulate both natural and rainfall conditions. The weak intercalation was composed of single-material silty clay, and the landslide mass was composed of red-bed sandstone. A combination of photography, pore water pressure measurements and earth pressure measurements were used to examine the relationship between the pore water pressure, earth pressure and failure modes. When the slope experiences overall instability, the curves of the earth pressure and pore water pressure dramatically decrease. The results reveal that the failure shear surface largely depends on the differential creep caused by the properties of the rock mass and the rainfall infiltration.展开更多
Electromechanical product's reliability is affected by uncertainty as well as performance degeneration during its life cycle.The present reliability and performance integrating modeling methods have obvious defici...Electromechanical product's reliability is affected by uncertainty as well as performance degeneration during its life cycle.The present reliability and performance integrating modeling methods have obvious deficiencies in long period reliability analysis and assessment when applied to such system.A novel integrating modeling method based on physics of failure(PoF)and a simulation algorithm that considers uncertainty and degeneration are proposed in this paper to compute maintenance free operation period or maintenance free operation period survivability which is used to assess long period reliability of system.Furthermore,the concept design of this kind of software based on the above theory is also introduced.A case study of servo valve demonstrates the feasibility of the method and usability of the software in this research.展开更多
A general failure probability simulation and deviation evaluation methods were presented for fuzzy safety state and fuzzy failure state. And the corresponding number integral method was simultaneously established. As ...A general failure probability simulation and deviation evaluation methods were presented for fuzzy safety state and fuzzy failure state. And the corresponding number integral method was simultaneously established. As the distribution of state variable and the membership of the state variable to the fuzzy safety set were normal, the general failure probability of the single failure mode had precise analytic solution, which was used to verify the precision of the presented methods. The results show that the evaluation of the simulation method convergences to the analytic solution with the number increase of the sampling. The above methods for the single failure mode was extended to the multi-mode by the expansion and probability principles. The presented methods were applied to the engineering problem. For the number of significant mode is not too many, the high precision solution can be given by the presented number simulation and number integral methods, which is illustrated by the engineering examples. In addition, the application scope of the methods was discussed.展开更多
Based on an essential assumption of meso-heterogeneity of material, the macro characteristic of composite reinfiorced with particles, the crack initiation, propagation and the failure process in composite were studied...Based on an essential assumption of meso-heterogeneity of material, the macro characteristic of composite reinfiorced with particles, the crack initiation, propagation and the failure process in composite were studied by using a numerical code. The composite is subjected to a uniaxial tension, aact stiff or soft particles are distributed at random manner but without overlapping or contacting. The effect of reinforcement particle properties on the fracture process aact mechanism of composite with brittle matrix, furthermore, the influence of the particle volumetric fraction is also investigated. Numerical results present the different failure mode and re-produce the crack initiation, propagation aurl coalescence in brittle aurl heterogeneons matrix. The mechanism of sach failure was also elucidated.展开更多
Considering the heterogeneity of geomechanical materials, seismicity during brittle rock failure under compressive loading on the sample with an original weak zone is simulated by using rock failure process analysis c...Considering the heterogeneity of geomechanical materials, seismicity during brittle rock failure under compressive loading on the sample with an original weak zone is simulated by using rock failure process analysis code (RFPA2D). The run-through process of weak zone, the forming of new fault and associated micro-seismicities are studied. The modeling demonstrates the total process of source development of earthquake from deformation, micro-failure to collapse and the behavior of temporal-spatial distribution of micro-seismicities. The stress, strain and the temporal-spatial distribution of micro-seismicities life-likely portrayed the phenomena of localization and temporal-spatial transitions, which is similar to those observed in our real crust. Also, the results obtained in simulations are in agreement with or similar to the reported experimental observations.展开更多
The reliability assessment model of k /N system is built based on Copula function theory considering the failure correlativity existing among components,and then a simulation strategy is presented on the foundation of...The reliability assessment model of k /N system is built based on Copula function theory considering the failure correlativity existing among components,and then a simulation strategy is presented on the foundation of agent technique.The components and equipment entity model are designed according to the modeling technique above to describe the operation relationship during the mission phase,and then the simulation system for the assessment of product reliability is completed.And at last,an example is given with different material support programs.The research result has shown that the relevance existing in components has effect on the confirmation and optimization of maintenance strategy.展开更多
In the engineering.to ensure the quality and safety,it is necessary to carry out reliability analysis on it.When conducting reliability analysis in engineering.a 1arge rumber of small1 failure probability problems wil...In the engineering.to ensure the quality and safety,it is necessary to carry out reliability analysis on it.When conducting reliability analysis in engineering.a 1arge rumber of small1 failure probability problems will be encountered.For such problems,the traditional Monte Carlo method needs a 1ot of samples,and the calculation efficiency is extremely 1ow,while the subset sinmulation method can efficiently estimate the relLability index of the small failure probability problem with litle samples.Therefore,this paper takes the application of the subset simulation method in the reliability analysis of the small failure probability structure as the object,constructs the reliability analysis method of the single failure mode of the system and applies the method to a mathematical example and a single-story gate.Through the rigid frame example,it can be seen that this method is beneficial to improve the calculation efficiency and accuracy.展开更多
Among various power system disturbances,cascading failures are considered the most serious and extreme threats to grid operations,potentially leading to significant stability issues or even widespread power blackouts....Among various power system disturbances,cascading failures are considered the most serious and extreme threats to grid operations,potentially leading to significant stability issues or even widespread power blackouts.Simulating power systems’behaviors during cascading failures is of great importance to comprehend how failures originate and propagate,as well as to develop effective preventive and mitigative control strategies.The intricate mechanism of cascading failures,characterized by multi-timescale dynamics,presents exceptional challenges for their simulations.This paper provides a comprehensive review of simulation models for cascading failures,providing a systematic categorization and a comparison of these models.The challenges and potential research directions for the future are also discussed.展开更多
The anchoring capacity of the anchor cable is closely related to the bonding length and radial pressure conditions.Through field pull-out tests,theoretical analysis,numerical simulation,and industrial tests,this study...The anchoring capacity of the anchor cable is closely related to the bonding length and radial pressure conditions.Through field pull-out tests,theoretical analysis,numerical simulation,and industrial tests,this study clarifies the relationship between radial pressure and bonding length for the ultimate pullout force and reveals the microscopic failure process of the resin-rock interface in the anchoring system.The results show that the ultimate load increases with the increase of bonding length in three different stages:rapid,slow,and uniform growth.The new mechanical model developed considering radial pressure describes the inverse relationship between radial pressure and the plastic zone on the bonding section,and quantifies the reinforcing effect of confining pressure on the anchoring force.During the pull-out process of the anchor cable,the generation of failure cracks is in the order of orifice,bottom,and middle of the hole.Radial pressure can effectively enhance the ultimate pull-out force,alleviate the oscillation increase of pull-out force,and inhibit resin cracking,but will produce an external crushing zone.It also reveals the synergistic effect between bonding length and radial pressure,and successfully carries out industrial tests of anchor cable support,which ensures the stability of the stope roof and provides an important reference for the design of anchor cable support in deep high-stress mines.展开更多
Acquiring pristine deep lunar regolith cores with appropriate drilling tools is crucial for deciphering the lunar geological history.Conventional thick-walled drill bits are inherently limited in obtaining deep lunar ...Acquiring pristine deep lunar regolith cores with appropriate drilling tools is crucial for deciphering the lunar geological history.Conventional thick-walled drill bits are inherently limited in obtaining deep lunar regolith samples,whereas thin-walled coring bits offer a promising solution for lunar deep drilling.To support future lunar deep exploration missions,this study systematically investigates the failure mechanisms of lunar regolith induced by thin-walled drilling tools.Firstly,five thin-walled bit configurations were designed and evaluated based on drilling load,coring efficiency,and disturbance minimization,with Bit D demonstrating optimal overall performance.And the interaction mechanisms between differently configured coring bits and large-particle lunar regolith were elucidated.Coring experiments under critical drilling parameters revealed an operational window for the feed-to-rotation ratio(FRR of 2.0–2.5),effectively balancing drilling load and core recovery rate.Furthermore,a novel theoretical framework was developed to characterize dynamic drilling load parameters,supported by experimental validation.Based on these findings,practical strategies are proposed to mitigate drilling-induced disturbances,including parameter optimization and bit structural improvements.This research could provide valuable insights for designing advanced lunar deep drilling tools and developing drilling procedures.展开更多
The rock mass failure induced by deep mining exhibits pronounced spatial heterogeneity and diverse mechanisms,with its microseismic responses serving as effective indicators of regional failure evolution and instabili...The rock mass failure induced by deep mining exhibits pronounced spatial heterogeneity and diverse mechanisms,with its microseismic responses serving as effective indicators of regional failure evolution and instability mechanisms.Focusing on the Level VI stope sublayers in the Jinchuan#2 mining area,this study constructs a 24-parameter index system encompassing time-domain features,frequency-domain features,and multifractal characteristics.Through manifold learning,clustering analysis,and hybrid feature selection,15 key indicators were extracted to construct a classification framework for failure responses.Integrated with focal mechanism inversion and numerical simulation,the failure patterns and corresponding instability mechanisms across different structural zones were further identified.The results reveal that multiscale microseismic characteristics exhibit clear regional similarities.Based on the morphological features of radar plots derived from the 15 indicators,acoustic responses were classified into four typical types,each reflecting distinct local failure mechanisms,stress conditions,and plastic zone evolution.Moreover,considering dominant instability factors and rupture modes,four representative rock mass instability models were proposed for typical failure zones within the stope.These findings provide theoretical guidance and methodological support for hazard prediction,structural optimization,and disturbance control in deep metal mining areas.展开更多
现有的基于失效物理(physics of failure,PoF)模型的可靠性预计只能计算电子产品在寿命周期内经历单一典型任务剖面的失效时间。本文提出了一种基于失效物理模型,并利用蒙特卡罗仿真定量分析电子产品在寿命周期内实际经历多任务剖面的...现有的基于失效物理(physics of failure,PoF)模型的可靠性预计只能计算电子产品在寿命周期内经历单一典型任务剖面的失效时间。本文提出了一种基于失效物理模型,并利用蒙特卡罗仿真定量分析电子产品在寿命周期内实际经历多任务剖面的可靠性水平的新方法。将该方法应用于某机载电子设备的平均失效前时间(mean time to failure,MTTF)的计算,建立失效率和可靠度的时间函数,与目前国内工程实践中常用的失效率经验模型法以及设备可靠性强化试验的结果进行了对比分析。结果表明,该方法不仅可以计算可靠性参数,而且通过分析与计算过程可发现设计薄弱环节与可靠性参数的定量关系,有效指导设计改进。展开更多
基金Projects(U23A2060,42177143)supported by the National Natural Science Foundation of China。
文摘To elucidate the influence of confining pressure on microcrack evolution and macroscopic failure mechanisms in granite,a multi-perspective approach was adopted.This approach combined triaxial compression tests,acoustic emission(AE)monitoring,and PFC simulations.The results show that:1)Confining pressure exhibits a pronounced linear correlation with both yield strength and compressive strength.The enhancement of confining pressure significantly improves the deformability of granite and promotes a progressive shift in failure mechanism from brittle rupture to ductile deformation;2)Increasing confining pressure elevates the stress threshold for microcrack initiation and suppresses crack propagation.As a result,the proportion of shear cracks increases(based on AE analysis)from 18.71%to 61.2%,marking a transition in the dominant failure mode from tensile to shear;3)Confining pressure facilitates the development of grain boundary shear cracks(GBSCs),establishing the primary damage pathways.In addition,local stress concentrations under high confinement conditions trigger intragranular cracking.This highlights the regulatory effect of confining pressure on microcrack evolution.
基金Financial support to complete this study was provided in part by National Natural Science Foundation of China(52109119)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(China Institute of Water Resources and Hydropower Research)(IWHR-SKL-202202)+1 种基金the China Postdoctoral Science Foundation Project(2022M723408)the Systematic Project of Guangxi Key Laboratory of Disaster Prevention and Engineering Safety(2020ZDK007)。
文摘The stability of slopes and tunnels is controlled by rock discontinuities,and the rock discontinuities roughness and the sliding direction play a signifcant role in shear failure.However,three-dimensional roughness evaluation considering shear directions is scare,and the internal shear fracturing processes,micromechanical mechanisms and failure precursor of rock discontinuities are not well understood.Therefore,this study proposes a novel roughness evaluation index to quantitatively analyze the anisotropic characteristics of rock discontinuities.In conjunction with shear tests,a novel 3D-GBM modelling method considering the micromineral constituent and particle size distribution characteristics of granite as well as the geometric shape of discontinuities was realized.The strength,macro and micro-fracture characteristics,visual anisotropic shear evolution process and microfailure mechanism of granite discontinuities at diferent roughness and shear direction were investigated.Finally,the spatial and temporal evolutions of AE parameter b-value and magnitude M were further analyzed to reveal the shear fracture precursor of granite discontinuities.
基金sponsored by the National Natural Science Foundation of China(Grant No.12002173,12262027)Research start-up project of Inner Mongolia University of Technology(No.2200000924)key Lab.of University of Geological Hazards and Geotechnical Engineering Defense in Sandy and Drought Regions,Inner Mongolia Autonomous.
文摘Microbially induced calcium carbonate precipitation(MICP)technology can induce calcium carbonate crystals with cementation and stable performance in the process of microbial metabolism or enzymization through the regulation of environmental factors MICP can be used as a cementing agent to cement cohesionless sand particles to form the materials with the characteristics of higher strength,better durability and environmental friendli-ness,as well as a good engineering application prospect.In this paper,the shear strength of sand column was tested by triaxial compression tests,and the strength index was obtained.In order to further study the micro-strength mechanism and the failure process,based on the discrete element method,a numerical model of MICP cemented sand column was established considering the factors of matrix soil particle gradation,particle mor-phology,content ratio of induced calcium carbonate,pore distribution characteristics,inter-particle cementation and so on.The failure process of MICP cemented sand column under load was analysed by numerical simulation,and the reliability of the numerical model was tested by combining with the stress intensity curve of samples under test conditions.The results indicate that compared with the actual triaxial tests of MICP cemented sand column,although there are deviations in stress and strain,cohesion and internal friction angle,the numerical simulation shows similar development law and intensity amplitude,and the same failure trend.The work in this paper verifies the reliability of the numerical model and provides a theoretical basis for the subsequent analysis of the factors influencing the geotechnical mechanical properties of biomineralized materials.
基金supported by the Graduate Degree Thesis Innovation Foundation of Central South University (No.2009ssxt226)
文摘In order to investigate the failure process of brittle rock under triaxial compression through both experimental and numerical approaches, the particle simulation method was used in numerical simulations and the simulated results were compared with those of the experiment. The numerical simulation results, such as fracture propagation, microcrack distribution, stress-strain response, and damage patterns, were discussed in detail. The simulated results under various confining pressures （0-60 MPa） are in good agreement with the experimental results. The simulated results reveal that rock failure is caused by axial splitting under uniaxial compression. As the confining pressure increases, rock failure occurs in a few localized shear planes and the rock mechanical behavior is changed from brittle to ductile. Consequently, the peak failure strength, microcrack numbers, and the shear plane angle increase, but the ratio of tensile to shear microcracks decreases. The damage formation during the compression simulations indicates that the particle simulation method can produce similar behaviors as those observed through laboratory compression tests.
基金financial support from the National Key R&D Program of China(No.2018YFC0604703)National Natural Science Foundation of China(Nos.51804181,51874190,and 52074168)Key R&D Program of Shandong Province(No.2019GSF111020)。
文摘Large and super-large section chamber groups in coal mines are frequently affected by dynamic loads resulting from production activities such as roadway driving and blasting.The stability of the surrounding rock is poor,and it is difficult to control.In this paper,a similar simulation test was used to study the deformation and evolution laws of the surrounding rock of a triangle-shaped chamber group under different dynamic loads.The results showed that under dynamic loading,the vertical stress of the surrounding rock of the chamber group increased in an oscillatory form.The maximum stress concentration coefficient reached 4.09.The damage degree of the roof was greater than that of the two sides.The deformation of the roof was approximately 1.2 times that of the two sides.For the chamber closer to the power source,the stress oscillation amplitude of the surrounding rock was larger,and the failure was more serious.The force of the anchorage structure showed a phased increasing characteristic;additionally,the force of the anchorage structure on the adjacent side of the chambers was greater than that on the other side.This study reveals the deformation and failure evolution laws of the surrounding rock of large section chamber groups under dynamic loading.
基金Suppirted by the Programme of Introducing Talents of Discipline to Universities(B07019)
文摘This paper focuses on the research of a semi-submersible platform equipped with a DP-assisted mooring system. Based on the working principles of the DP-assisted mooring system and the model of the platform motion, a time domain simulation program is applied to analyze the impact, in the case of one line failure, on the platform motion, power consumption of the thrusters and the tension of the mooring lines. The results show that, under the 10-year wind dominant, a one line failure will have little impact on the tension of the mooring lines. When the failure line is windward, the power consumption will increase greatly with a weakened position of accuracy. However when the failure line is leeward, the power consumption will be reduced with a partly strengthened oosition of accuracy.
基金provided by the National Natural Science Foundation of China(Nos.51322401,51309222,51323004,51579239 and 51574223)the Opening Project Fund of Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation(No.CDPM2014KF03)+2 种基金the State Key Laboratory for GeoMechanics Opening Project Fund of Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and MitigationDeep Underground Engineering,China University of Mining&Technology(No.SKLGDUEK1305)China Postdoctoral Science Foundation(Nos.2014M551700and 2013M531424)
文摘Based on the safety coefficient method,which assigns rock failure criteria to calculate the rock mass unit,the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the fractured zone in the roadway.This will provide the basis numerical simulation to calculate the surrounding rock fractured zone in a roadway.Using the single factor and multi-factor orthogonal test method,the evolution law of roadway surrounding rock displacements,plastic zone and stress distribution under different conditions is studied.It reveals the roadway surrounding rock burst evolution process,and obtains five kinds of failure modes in deep soft rock roadway.Using the fuzzy mathematics clustering analysis method,the deep soft surrounding rock failure model in Zhujixi mine can be classified and patterns recognized.Compared to the identification results and the results detected by geological radar of surrounding rock loose circle,the reliability of the results of the pattern recognition is verified and lays the foundations for the support design of deep soft rock roadways.
文摘Rainfall is one of the most important factors contributing to landslides, and gentle bedding incline, high-rainfall induced landslides are common throughout the world. Field observations and theoretical analyses have been used to assess slope instability caused by permeability variation. In this study, the influence of rainfall infiltration on gentle bedding incline slope behaviour was investigated using a centrifuge physical simulation test. The magnitude, pattern and development of pore water and earth pressure at the interface;the shear failure surface features;and the corresponding deformation and failure processes were considered. A model with interbedded sand and mud was created, and a centrifuge was used to simulate both natural and rainfall conditions. The weak intercalation was composed of single-material silty clay, and the landslide mass was composed of red-bed sandstone. A combination of photography, pore water pressure measurements and earth pressure measurements were used to examine the relationship between the pore water pressure, earth pressure and failure modes. When the slope experiences overall instability, the curves of the earth pressure and pore water pressure dramatically decrease. The results reveal that the failure shear surface largely depends on the differential creep caused by the properties of the rock mass and the rainfall infiltration.
基金National Natural Science Foundation of China(No.61304218)Beijing Natural Science Foundation,China(No.3153027)
文摘Electromechanical product's reliability is affected by uncertainty as well as performance degeneration during its life cycle.The present reliability and performance integrating modeling methods have obvious deficiencies in long period reliability analysis and assessment when applied to such system.A novel integrating modeling method based on physics of failure(PoF)and a simulation algorithm that considers uncertainty and degeneration are proposed in this paper to compute maintenance free operation period or maintenance free operation period survivability which is used to assess long period reliability of system.Furthermore,the concept design of this kind of software based on the above theory is also introduced.A case study of servo valve demonstrates the feasibility of the method and usability of the software in this research.
文摘A general failure probability simulation and deviation evaluation methods were presented for fuzzy safety state and fuzzy failure state. And the corresponding number integral method was simultaneously established. As the distribution of state variable and the membership of the state variable to the fuzzy safety set were normal, the general failure probability of the single failure mode had precise analytic solution, which was used to verify the precision of the presented methods. The results show that the evaluation of the simulation method convergences to the analytic solution with the number increase of the sampling. The above methods for the single failure mode was extended to the multi-mode by the expansion and probability principles. The presented methods were applied to the engineering problem. For the number of significant mode is not too many, the high precision solution can be given by the presented number simulation and number integral methods, which is illustrated by the engineering examples. In addition, the application scope of the methods was discussed.
文摘Based on an essential assumption of meso-heterogeneity of material, the macro characteristic of composite reinfiorced with particles, the crack initiation, propagation and the failure process in composite were studied by using a numerical code. The composite is subjected to a uniaxial tension, aact stiff or soft particles are distributed at random manner but without overlapping or contacting. The effect of reinforcement particle properties on the fracture process aact mechanism of composite with brittle matrix, furthermore, the influence of the particle volumetric fraction is also investigated. Numerical results present the different failure mode and re-produce the crack initiation, propagation aurl coalescence in brittle aurl heterogeneons matrix. The mechanism of sach failure was also elucidated.
基金The Development Program on National Key Basic Researches under the Project Mechanism and Prediction of Continental Strong Earthquakes (G19980407) State Natural Science Foundation (49974009).
文摘Considering the heterogeneity of geomechanical materials, seismicity during brittle rock failure under compressive loading on the sample with an original weak zone is simulated by using rock failure process analysis code (RFPA2D). The run-through process of weak zone, the forming of new fault and associated micro-seismicities are studied. The modeling demonstrates the total process of source development of earthquake from deformation, micro-failure to collapse and the behavior of temporal-spatial distribution of micro-seismicities. The stress, strain and the temporal-spatial distribution of micro-seismicities life-likely portrayed the phenomena of localization and temporal-spatial transitions, which is similar to those observed in our real crust. Also, the results obtained in simulations are in agreement with or similar to the reported experimental observations.
文摘The reliability assessment model of k /N system is built based on Copula function theory considering the failure correlativity existing among components,and then a simulation strategy is presented on the foundation of agent technique.The components and equipment entity model are designed according to the modeling technique above to describe the operation relationship during the mission phase,and then the simulation system for the assessment of product reliability is completed.And at last,an example is given with different material support programs.The research result has shown that the relevance existing in components has effect on the confirmation and optimization of maintenance strategy.
基金funded by the Sichuan Science and Technology Innovation Seedling Project Funding Project (Grant No.2021112).
文摘In the engineering.to ensure the quality and safety,it is necessary to carry out reliability analysis on it.When conducting reliability analysis in engineering.a 1arge rumber of small1 failure probability problems will be encountered.For such problems,the traditional Monte Carlo method needs a 1ot of samples,and the calculation efficiency is extremely 1ow,while the subset sinmulation method can efficiently estimate the relLability index of the small failure probability problem with litle samples.Therefore,this paper takes the application of the subset simulation method in the reliability analysis of the small failure probability structure as the object,constructs the reliability analysis method of the single failure mode of the system and applies the method to a mathematical example and a single-story gate.Through the rigid frame example,it can be seen that this method is beneficial to improve the calculation efficiency and accuracy.
基金supported by UT-Battelle,LLC under Contract No.DE-AC05-00OR22725 with the U.S.Department of Energy.
文摘Among various power system disturbances,cascading failures are considered the most serious and extreme threats to grid operations,potentially leading to significant stability issues or even widespread power blackouts.Simulating power systems’behaviors during cascading failures is of great importance to comprehend how failures originate and propagate,as well as to develop effective preventive and mitigative control strategies.The intricate mechanism of cascading failures,characterized by multi-timescale dynamics,presents exceptional challenges for their simulations.This paper provides a comprehensive review of simulation models for cascading failures,providing a systematic categorization and a comparison of these models.The challenges and potential research directions for the future are also discussed.
基金Financial supports for this work,provided by the National Natural Science Foundation Project of China(No.52374152)the Guangxi Science and Technology Plan Project of China(No.2022AB31023)the National Basic Research Development Program of China(No.2022YFC2904602)are gratefully acknowledged。
文摘The anchoring capacity of the anchor cable is closely related to the bonding length and radial pressure conditions.Through field pull-out tests,theoretical analysis,numerical simulation,and industrial tests,this study clarifies the relationship between radial pressure and bonding length for the ultimate pullout force and reveals the microscopic failure process of the resin-rock interface in the anchoring system.The results show that the ultimate load increases with the increase of bonding length in three different stages:rapid,slow,and uniform growth.The new mechanical model developed considering radial pressure describes the inverse relationship between radial pressure and the plastic zone on the bonding section,and quantifies the reinforcing effect of confining pressure on the anchoring force.During the pull-out process of the anchor cable,the generation of failure cracks is in the order of orifice,bottom,and middle of the hole.Radial pressure can effectively enhance the ultimate pull-out force,alleviate the oscillation increase of pull-out force,and inhibit resin cracking,but will produce an external crushing zone.It also reveals the synergistic effect between bonding length and radial pressure,and successfully carries out industrial tests of anchor cable support,which ensures the stability of the stope roof and provides an important reference for the design of anchor cable support in deep high-stress mines.
基金supported by the National Natural Science Foundation of China(Nos.52225403,52434004,and 52404365)the National Key Research and Development Program of China(No.2023YFF0615404)the Scientific Instrument Developing Project of Shenzhen University.
文摘Acquiring pristine deep lunar regolith cores with appropriate drilling tools is crucial for deciphering the lunar geological history.Conventional thick-walled drill bits are inherently limited in obtaining deep lunar regolith samples,whereas thin-walled coring bits offer a promising solution for lunar deep drilling.To support future lunar deep exploration missions,this study systematically investigates the failure mechanisms of lunar regolith induced by thin-walled drilling tools.Firstly,five thin-walled bit configurations were designed and evaluated based on drilling load,coring efficiency,and disturbance minimization,with Bit D demonstrating optimal overall performance.And the interaction mechanisms between differently configured coring bits and large-particle lunar regolith were elucidated.Coring experiments under critical drilling parameters revealed an operational window for the feed-to-rotation ratio(FRR of 2.0–2.5),effectively balancing drilling load and core recovery rate.Furthermore,a novel theoretical framework was developed to characterize dynamic drilling load parameters,supported by experimental validation.Based on these findings,practical strategies are proposed to mitigate drilling-induced disturbances,including parameter optimization and bit structural improvements.This research could provide valuable insights for designing advanced lunar deep drilling tools and developing drilling procedures.
基金financial support from the Distinguished Youth Funds of the National Natural Science Foundation of China(No.52425403)the Hunan Province Graduate Research Innovation Project of China(No.CX20230168)。
文摘The rock mass failure induced by deep mining exhibits pronounced spatial heterogeneity and diverse mechanisms,with its microseismic responses serving as effective indicators of regional failure evolution and instability mechanisms.Focusing on the Level VI stope sublayers in the Jinchuan#2 mining area,this study constructs a 24-parameter index system encompassing time-domain features,frequency-domain features,and multifractal characteristics.Through manifold learning,clustering analysis,and hybrid feature selection,15 key indicators were extracted to construct a classification framework for failure responses.Integrated with focal mechanism inversion and numerical simulation,the failure patterns and corresponding instability mechanisms across different structural zones were further identified.The results reveal that multiscale microseismic characteristics exhibit clear regional similarities.Based on the morphological features of radar plots derived from the 15 indicators,acoustic responses were classified into four typical types,each reflecting distinct local failure mechanisms,stress conditions,and plastic zone evolution.Moreover,considering dominant instability factors and rupture modes,four representative rock mass instability models were proposed for typical failure zones within the stope.These findings provide theoretical guidance and methodological support for hazard prediction,structural optimization,and disturbance control in deep metal mining areas.
文摘现有的基于失效物理(physics of failure,PoF)模型的可靠性预计只能计算电子产品在寿命周期内经历单一典型任务剖面的失效时间。本文提出了一种基于失效物理模型,并利用蒙特卡罗仿真定量分析电子产品在寿命周期内实际经历多任务剖面的可靠性水平的新方法。将该方法应用于某机载电子设备的平均失效前时间(mean time to failure,MTTF)的计算,建立失效率和可靠度的时间函数,与目前国内工程实践中常用的失效率经验模型法以及设备可靠性强化试验的结果进行了对比分析。结果表明,该方法不仅可以计算可靠性参数,而且通过分析与计算过程可发现设计薄弱环节与可靠性参数的定量关系,有效指导设计改进。
