Granite residual soil slope is often destroyed,which poses great threats to Rong County in southeastern Guangxi,China.Heavy rainfall and fissures are the major triggering and internal factors.The fissure that controls...Granite residual soil slope is often destroyed,which poses great threats to Rong County in southeastern Guangxi,China.Heavy rainfall and fissures are the major triggering and internal factors.The fissure that controls the slope stability and the associated failure mechanisms remain unclear.The purpose of this study was to identify the controlling fissures through field investigation,elucidate the effect of its position,and analyze the failure process and hydrological response of residual soil slope through artificial flume model tests.The results comprised five aspects.(1)Surface weathering and unloading fissures could affect slope stability.(2)The failure processes with different fissure positions exhibited inconsistent characteristics.(3)The volume moisture content(VMC)had the most direct response at the fissure tip.The corresponding infiltration rate was the highest.The response time of pore water pressure(PWP)was longer than that of VMC.Fluctuations in PWP were associated with VMC and changes in the soil microstructure due to local deformation.(4)Slope failure was accompanied by serious soil erosion.This could be attributed to the infiltration direction and the interaction between soil and water.(5)Fissured soil slopes experienced five similar failure processes:sheet erosion and partial failure of the slope foot,occurrence of preferential flow and enlargement of the sliding area,creep deformation and tension fissure emergence,block sliding and gully erosion,and flow-slip.展开更多
Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in undergroun...Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in underground engineering.To reveal the effect of this way,the uniaxial compression experiments with PSC monitoring were conducted on three types of coal-rock combination samples with different strength combinations.The mechanism explanation of PSCs are investigated by resistivity test,atomic force microscopy(AFM)and computed tomography(CT)methods,and a PSC flow model based on progressive failure process is proposed.The influence of strength combinations on PSCs in the progressive failure process are emphasized.The results show the PSC responses between rock part,coal part and the two components are different,which are affected by multi-scale fracture characteristics and electrical properties.As the rock strength decreases,the progressive failure process changes obviously with the influence range of interface constraint effect decreasing,resulting in the different responses of PSC strength and direction in different parts to fracture behaviors.The PSC flow model is initially validated by the relationship between the accumulated charges of different parts.The results are expected to provide a new reference and method for mining design and roadway quality assessment.展开更多
The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is consider...The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is considered. First, based on the assumption of cumulative shock, the probabilistic models for hard failure and soft failure are built respectively. On this basis, the dependent competing failure model involving degradation and shock processes is established. Furthermore, the situation of the shifting-threshold is also considered, in which the hard failure threshold value decreases to a lower level after the arrival of a certain number of shocks. A case study of fatigue crack growth is given to illustrate the proposed models. Numerical results show that shock has a significant effect on the failure process; meanwhile, the effect will be magnified when the value of the hard threshold shifts to a lower level.展开更多
No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. TE (the...No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. TE (the time that the end of impact force) and TF (the time that members are broken) are two key times in the failure process. Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear. Then three steps of energy transfer are summarized, i.e. energy applying, energy loss and energy transfer, energy consump-tion. Based on the three steps, energy transfer process for the failure reticulated dome under once impact is introduced. Energy transmissibility and local loss ratio are put forward firstly to obtain EL F(the energy left in the main reticulated dome) from the initial kinetic energy of impactor. More-over, the distribution of failure modes is decided by EL F which leads to the maximum dynamic re-sponse of the reticulated dome, but not by the initial impact kinetic energy of impactor.展开更多
In order to resolve grid distortions in finite element method(FEM), the meshless numerical method which is called general particle dynamics(GPD) was presented to simulate the large deformation and failure of geomateri...In order to resolve grid distortions in finite element method(FEM), the meshless numerical method which is called general particle dynamics(GPD) was presented to simulate the large deformation and failure of geomaterials. The Mohr-Coulomb strength criterion was implemented into the code to describe the elasto-brittle behaviours of geomaterials while the solid-structure(reinforcing pile) interaction was simulated as an elasto-brittle material. The Weibull statistical approach was applied to describing the heterogeneity of geomaterials. As an application of general particle dynamics to slopes, the interaction between the slopes and the reinforcing pile was modelled. The contact between the geomaterials and the reinforcing pile was modelled by using the coupling condition associated with a Lennard-Jones repulsive force. The safety factor, corresponding to the minimum shear strength reduction factor "R", was obtained, and the slip surface of the slope was determined. The numerical results are in good agreement with those obtained from limit equilibrium method and finite element method. It indicates that the proposed geomaterial-structure interaction algorithm works well in the GPD framework.展开更多
Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The res...Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The results show that the propagation phenomenon of stress wave in the surrounding rock of tunnel and the failure process of surrounding rock under explosive stress waves are reproduced realistically by using numerical code RFPA2O; from the failure process of surrounding rock, the place at which surrounding rock fractures is transferred because of tunnel reinforcing, and the rockfall and collapse caused by failure of surrounding rock are restrained by tunnel reinforcing; furthermore, the absolute values of peak values of major principal stress, and the minimal principal stress and shear stress at center point of tunnel roof are reduced because of tunnel reinforcing, and the displacement at center point of runnel roof is reduced as well, consequently the stability of tunnel increases.展开更多
Due to the extreme complexity of mechanical response of soft surrounding rock(SR) around a tunnel under high geostatic stress conditions, the integration of physical and numerical modeling techniques was adopted. Base...Due to the extreme complexity of mechanical response of soft surrounding rock(SR) around a tunnel under high geostatic stress conditions, the integration of physical and numerical modeling techniques was adopted. Based on the similarity theory, new composite-similar material was developed, which showed good agreement with the similarity relation and successfully simulated physico-mechanical properties(PMP) of deep buried soft rock. And the 800 mm×800 mm×200 mm physical model(PM) was conducted, in which the endoscopic camera technique was adopted to track the entire process of failure of the model all the time. The experimental results indicate that the deformation of SR around a underground cavern possessed the characteristics of development by stages and in delay, and the initial damage of SR could induce rapid failure in the later stage, and the whole process could be divided into three stages, including the localized extension of crack(the horizontal load(HL) was in the range of 130 k N to 170 k N, the vertical load(VL) was in the range of 119 k N to 153.8 k N), rapid crack coalescence(the HL was in the range of 170 k N to 210 k N, the VL was in the range of 153.8 k N to 182.5 k N) and residual strength(the HL was greater than 210 k N, the VL was greater than 182.5 k N). Under the high stress conditions, the phenomenon of deformation localization in the SR became serious and different space positions show different deformation characteristics. In order to further explore the deformation localization and progressive failure phenomenon of soft SR around the deeply buried tunnel, applying the analysis software of FLAC3 D three-dimensional explicit finite-difference method, based on the composite strain-softening model of Mohr-Coulomb shear failure and tensile failure, the calculation method of large deformation was adopted. Then, the comparative analysis between the PM experiment and numerical simulation of the three centered arch tunnels was implemented and the relationship of deformation localization and progressive failure of SR around a tunnel under high stress conditions was discussed.展开更多
In order to study the failure process of an anchorage structure and the evolution law of the body＇s defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods （DSCM）. T...In order to study the failure process of an anchorage structure and the evolution law of the body＇s defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods （DSCM）. The stress distribution of the anchorage interface was investigated using the particle flow numerical simulation method. The results indicate that there are three stages in the deformation and fail- ure process of an anchorage structure： elastic bonding stage, a de-bonding stage and a failure stage. The stress distribution in the interface controls the stability of the structure. In the elastic bonding stage, the shear stress peak point of the interface is close to the loading end, and the displacement field gradually develops into a ＂V＂ shape, in the de-bonding stage, there is a shear stress plateau in the center of the anchorage section, and shear strain localization begins to form in the deformation field. In the failure stage, the bonding of the interface fails rapidly and the shear stress peak point moves to the anchorage free end. The anchorage structure moves integrally along the macro-cracl~ The de-bonding stage is a research focus in the deformation and failure process of an anchorage structure, and plays an important guiding role in roadway support design and prediction of the stability of the surrounding rock.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
As the non-periodic inspections are common in practice,a two-stage inspection model based on a three-stage failure process is proposed. The two-stage inspection means that the system is inspected with the first inspec...As the non-periodic inspections are common in practice,a two-stage inspection model based on a three-stage failure process is proposed. The two-stage inspection means that the system is inspected with the first inspection interval T_1 and the second inspection interval T_2. Because of the three color schemes commonly used in industry,three stages are divided by the system lifetime:normal, minor defective and severe defective stages. Upon the failure of the system,replacement is carried out. Maintenance is done once identifying the severe defective stage. However,when the minor defective stage is identified by the second inspection interval T_2,action of halving the subsequent inspection interval is adopted.Otherwise,no action is required. Our objective function is to optimize the inspection intervals so as to minimize the expected cost per unit time. Finally,a numerical example is presented to illustrate the effectiveness of the proposed model.展开更多
RFPA is a numerical testing tool for realistic failure process analysis(RFPA)of rock,concrete,composites,and engineering structures.The RFPA solution offers perfect simulation tools for robust modelling of brittle mat...RFPA is a numerical testing tool for realistic failure process analysis(RFPA)of rock,concrete,composites,and engineering structures.The RFPA solution offers perfect simulation tools for robust modelling of brittle material failure and engineering structural damage.The RFPA family of 2D and 3D core products offers the full depth of analysis tools—from a conceptual simulation to advanced展开更多
Active tectonic movements and geological disasters frequently occur in the upper reaches of the Jinsha River,increasing the likelihood of landslides obstructing the river.Taking the ancient Rongcharong landslide dam f...Active tectonic movements and geological disasters frequently occur in the upper reaches of the Jinsha River,increasing the likelihood of landslides obstructing the river.Taking the ancient Rongcharong landslide dam failure events in the Suwalong reach as an example,this paper first analyzes the accuracy and applicability of the commonly used methods in calculating the peak flow of the dam failure,such as the empirical formula,the numerical method based on the physical mechanism,and the computational fluid dynamics(CFD)method.Then,the peak flood flow of the Rongcharong-dammed lake when it overflows the dam is determined to be 28393-64272 m~3/s.At the same time,the failure process of landslide dam due to flood erosion was elucidated using the CFD method,which can be divided into three stages:gradual erosion in the initial stage,rapid development in the middle stage,and gradual expansion in the final stage.Finally,the factors that affect the peak flow of floods are analyzed,and suggestions for emergency treatment of landslide dams are put forward.The findings of this research can serve as a valuable reference for disaster prevention and mitigation strategies to adapt to the increasing frequency of landslide-induced river blockages.展开更多
The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,co...The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,combining soft material with fractal,a composite pre-tightened multi-hierarchy tooth joint is proposed,and the bearing performance and failure process of the joint through experiments and finite element method under tensile load.First,the ultimate bearing capacity,load distribution ratio,and failure process of different hierarchies of teeth joints are studied through experiments.Then,the progressive damage models of different hierarchies of tooth joints are established,and experiments verify the validity of the finite element model.Finally,the effects of soft material and increasing tooth hierarchy on the failure process and bearing capacity of composite pre-tightened tooth joints are analyzed by the finite element method.The following conclusions can be drawn:(1)The embedding of soft materials changed the failure process of the joint.Increasing the tooth hierarchy can give the joint more load transfer paths,but the failure process of the joint is complicated.(2)Embedding soft materials and increasing the tooth hierarchy simultaneously can effectively improve the bearing capacity of composite pre-tightened tooth joints,which is 87.8%higher than that of traditional three-tooth joints.展开更多
Split Hopkinson pressure bar(SHPB)has been used to study the dynamic failure pattern of flattened mortar Brazilian disc under impact load.Each disc contains several prefabricated cracks paralleled to each other.Dynami...Split Hopkinson pressure bar(SHPB)has been used to study the dynamic failure pattern of flattened mortar Brazilian disc under impact load.Each disc contains several prefabricated cracks paralleled to each other.Dynamic FEM has also been adopted to simulate such failure behavior.The mechanism of crack initiation,propagation and cut-through have been scrutinized with both experimental and numerical approaches.Influence of the number of the prefabricated cracks on the specimen strength and acoustic emission(AE)performance can be observed and studied.The results show that the strength decreases and AE counts increases,when the number of the prefabricated cracks increases.展开更多
The sanding process caused by karstification in dolomite creates a special sandy dolomite stratum,where the frequent catastrophic instability of the surrounding rock occurred during tunnel construction.In this study,t...The sanding process caused by karstification in dolomite creates a special sandy dolomite stratum,where the frequent catastrophic instability of the surrounding rock occurred during tunnel construction.In this study,the micro-origin and macro-performance of the sandy dolomite stratum are first discussed.Then,a numerical model based on the coupling method between the discontinuous deformation analysis and smoothed particle hydrodynamics is proposed to depict the heterogeneous dolomite formation with different sanding degrees.Following,the mechanical behaviors of the heterogeneous dolomite samples under uniaxial compression are studied after calibrating the numerical parameters with the two single materials sampled from the tunnel site respectively.Further,the instability disasters of the dolomite surrounding rock with different sanding degrees are reproduced,and the failure behaviors of tunnels are explained with respect to the stress distribution and plastic zone.The obtained results show that the rotation and dislocation of the remained dolomite block contribute to the unsmooth stress–strain curve and deterioration in uniaxial compressive strength.However,the block serves as the skeleton in the transmission of field stress in underground space,which improves the stability of the formation.展开更多
A cascading failure of landslide dams caused by strong earthquakes or torrential rains in mountainous river valleys can pose great threats to people’s lives,properties,and infrastructures.In this study,based on the t...A cascading failure of landslide dams caused by strong earthquakes or torrential rains in mountainous river valleys can pose great threats to people’s lives,properties,and infrastructures.In this study,based on the three-dimensional Reynoldsaveraged Navier-Stokes equations(RANS),the renormalization group(RNG)k-εturbulence model,suspended and bed load transport equations,and the instability discriminant formula of dam breach side slope,and the explicit finite volume method(FVM),a detailed numerical simulation model for calculating the hydro-morphodynamic characteristics of cascading dam breach process has been developed.The developed numerical model can simulate the breach hydrograph and the dam breach morphology evolution during the cascading failure process of landslide dams.A model test of the breaches of two cascading landslide dams has been used as the validation case.The comparison of the calculated and measured results indicates that the breach hydrograph and the breach morphology evolution process of the upstream and downstream dams are generally consistent with each other,and the relative errors of the key breaching parameters,i.e.,the peak breach flow and the time to peak of each dam,are less than±5%.Further,the comparison of the breach hydrographs of the upstream and downstream dams shows that there is an amplification effect of the breach flood on the cascading landslide dam failures.Three key parameters,i.e.,the distance between the upstream and the downstream dams,the river channel slope,and the downstream dam height,have been used to study the flood amplification effect.The parameter sensitivity analyses show that the peak breach flow at the downstream dam decreases with increasing distance between the upstream and the downstream dams,and the downstream dam height.Further,the peak breach flow at the downstream dam first increases and then decreases with steepening of the river channel slope.When the flood caused by the upstream dam failure flows to the downstream dam,it can produce a surge wave that overtops and erodes the dam crest,resulting in a lowering of the dam crest elevation.This has an impact on the failure occurrence time and the peak breach flow of the downstream dam.The influence of the surge wave on the downstream dam failure process is related to the volume of water that overtops the dam crest and the erosion characteristics of dam material.Moreover,the cascading failure case of the Xiaogangjian and Lower Xiaogangjian landslide dams has also been used as the representative case for validating the model.In comparisons of the calculated and measured breach hydrographs and final breach morphologies,the relative errors of the key dam breaching parameters are all within±10%,which verify the rationality of the model is applicable to real-world cases.Overall,the numerical model developed in this study can provide important technical support for the risk assessment and emergency treatment of failures of cascading landslide dams.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
A engineering system is usually repairable, and failure process of a repairable by a failure point process. The power law model is a commonly used approach to model syst the em is often described failure point process...A engineering system is usually repairable, and failure process of a repairable by a failure point process. The power law model is a commonly used approach to model syst the em is often described failure point process. This paper introduces the concept and model for the failure process of repairable system. The method of parameter estimation is developed, and failure observations are fitted into a power-law model by using the least square method. Two applications of the pressent model are discussed according to the practical failure data of the central cooling system of a nuclear power plant. One application is determining the optimal overhaul time, and the other is evaluating the quality of maintenance. This paper provides references for the overhaul decision making and maintenance quality evaluation in reality.展开更多
In this paper, a new method is developed to model dependent failure behavior among failure mechanisms. Unlike the existing methods, the developed method models the root cause of the dependency explicitly, so that a de...In this paper, a new method is developed to model dependent failure behavior among failure mechanisms. Unlike the existing methods, the developed method models the root cause of the dependency explicitly, so that a deterministic model, rather than a probabilistic one, can be established. Three steps comprise the developed method. First, physics-of-failure（PoF） models are utilized to model each failure mechanism. Then, interactions among failure mechanisms are modeled as a combination of three basic relations, competition, superposition and coupling. This is the reason why the method is referred to as ＂compositional method＂. Finally, the PoF models and the interaction model are combined to develop a deterministic model of the dependent failure behavior. As a demonstration, the method is applied on an actual spool and the developed failure behavior model is validated by a wear test. The result demonstrates that the compositional method is an effective way to model dependent failure behavior.展开更多
Outburst floods caused by breaches of landslide dams may cause serious damages and loss of lives in downstream areas; for this reason the study of the dynamic of the process is of particular interest for hazard and ri...Outburst floods caused by breaches of landslide dams may cause serious damages and loss of lives in downstream areas; for this reason the study of the dynamic of the process is of particular interest for hazard and risk assessment. In this paper we report a field-scale landslide dam failure experiment conducted in Nantou County, in the central of Taiwan.The seismic signal generated during the dam failure was monitored using a broadband seismometer and the signal was used to study the dam failure process.We used the short-time Fourier transform(STFT) to obtain the time–frequency characteristics of the signal and analyzed the correlation between the power spectrum density(PSD) of the signal and the water level. The results indicate that the seismic signal generated during the process consisted of three components: a low-frequency band(0–1.5 Hz), an intermediate-frequency band(1.5–10 Hz) and a highfrequency band(10–45 Hz). We obtained the characteristics of each frequency band and the variations of the signal in various stages of the landslide dam failure process. We determined the cause for the signal changes in each frequency band and its relationship with the dam failure process. The PSD sediment flux estimation model was used to interpret the causes of variations in the signal energy before the dam failure and the clockwise hysteresis during the failure. Our results show that the seismic signal reflects the physical characteristics of the landslide dam failure process. The method and equipment used in this study may be used to monitor landslide dams and providing early warnings for dam failures.展开更多
基金financially supported by the National Natural Science Foundation of China(No.41901132)the Natural Scientific Project of Guangxi Zhuang Autonomous Region(Nos.2019GXNSFAA185015,2021GXNSFBA220025)+1 种基金the Interdisciplinary Scientific Research Foundation of Guangxi University(No.2022JCC026)the Project of Key Laboratory of Early Rapid Identification,Prevention and Control of Geological Diseases in Traffic Corridor of High Intensity Earthquake Mountainous Area of Yunnan Province(No.KLGDTC-2021-01)。
文摘Granite residual soil slope is often destroyed,which poses great threats to Rong County in southeastern Guangxi,China.Heavy rainfall and fissures are the major triggering and internal factors.The fissure that controls the slope stability and the associated failure mechanisms remain unclear.The purpose of this study was to identify the controlling fissures through field investigation,elucidate the effect of its position,and analyze the failure process and hydrological response of residual soil slope through artificial flume model tests.The results comprised five aspects.(1)Surface weathering and unloading fissures could affect slope stability.(2)The failure processes with different fissure positions exhibited inconsistent characteristics.(3)The volume moisture content(VMC)had the most direct response at the fissure tip.The corresponding infiltration rate was the highest.The response time of pore water pressure(PWP)was longer than that of VMC.Fluctuations in PWP were associated with VMC and changes in the soil microstructure due to local deformation.(4)Slope failure was accompanied by serious soil erosion.This could be attributed to the infiltration direction and the interaction between soil and water.(5)Fissured soil slopes experienced five similar failure processes:sheet erosion and partial failure of the slope foot,occurrence of preferential flow and enlargement of the sliding area,creep deformation and tension fissure emergence,block sliding and gully erosion,and flow-slip.
基金supported by National Key R&D Program of China(No.2022YFC3004705)the National Natural Science Foundation of China(Nos.52074280,52227901 and 52204249)National Natural Science Foundation of China Youth Fund(No.52104230).
文摘Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in underground engineering.To reveal the effect of this way,the uniaxial compression experiments with PSC monitoring were conducted on three types of coal-rock combination samples with different strength combinations.The mechanism explanation of PSCs are investigated by resistivity test,atomic force microscopy(AFM)and computed tomography(CT)methods,and a PSC flow model based on progressive failure process is proposed.The influence of strength combinations on PSCs in the progressive failure process are emphasized.The results show the PSC responses between rock part,coal part and the two components are different,which are affected by multi-scale fracture characteristics and electrical properties.As the rock strength decreases,the progressive failure process changes obviously with the influence range of interface constraint effect decreasing,resulting in the different responses of PSC strength and direction in different parts to fracture behaviors.The PSC flow model is initially validated by the relationship between the accumulated charges of different parts.The results are expected to provide a new reference and method for mining design and roadway quality assessment.
基金The National Natural Science Foundation of China(No.50405021)Graduate Training Innovative Projects Foundation of Jiangsu Province(No.CXLX12_0081)
文摘The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is considered. First, based on the assumption of cumulative shock, the probabilistic models for hard failure and soft failure are built respectively. On this basis, the dependent competing failure model involving degradation and shock processes is established. Furthermore, the situation of the shifting-threshold is also considered, in which the hard failure threshold value decreases to a lower level after the arrival of a certain number of shocks. A case study of fatigue crack growth is given to illustrate the proposed models. Numerical results show that shock has a significant effect on the failure process; meanwhile, the effect will be magnified when the value of the hard threshold shifts to a lower level.
基金Supported by National Natural Science Foundation of China(No.90715034)
文摘No failure, moderate failure, severe failure, and slight failure are the four failure modes generalized observed in the dynamic response of the single-layer reticulated dome under vertical impact load on apex. TE (the time that the end of impact force) and TF (the time that members are broken) are two key times in the failure process. Characteristics of dynamic responses at the two key times are shown in order to make the failure mechanism clear. Then three steps of energy transfer are summarized, i.e. energy applying, energy loss and energy transfer, energy consump-tion. Based on the three steps, energy transfer process for the failure reticulated dome under once impact is introduced. Energy transmissibility and local loss ratio are put forward firstly to obtain EL F(the energy left in the main reticulated dome) from the initial kinetic energy of impactor. More-over, the distribution of failure modes is decided by EL F which leads to the maximum dynamic re-sponse of the reticulated dome, but not by the initial impact kinetic energy of impactor.
基金Projects(51325903,51279218)supported by the National Natural Science Foundation of ChinaProject(cstc2013kjrcljrccj0001)supported by the Natural Science Foundation Project of CQ CSTC,ChinaProject(20130191110037)supported by Research fund by the Doctoral Program of Higher Education of China
文摘In order to resolve grid distortions in finite element method(FEM), the meshless numerical method which is called general particle dynamics(GPD) was presented to simulate the large deformation and failure of geomaterials. The Mohr-Coulomb strength criterion was implemented into the code to describe the elasto-brittle behaviours of geomaterials while the solid-structure(reinforcing pile) interaction was simulated as an elasto-brittle material. The Weibull statistical approach was applied to describing the heterogeneity of geomaterials. As an application of general particle dynamics to slopes, the interaction between the slopes and the reinforcing pile was modelled. The contact between the geomaterials and the reinforcing pile was modelled by using the coupling condition associated with a Lennard-Jones repulsive force. The safety factor, corresponding to the minimum shear strength reduction factor "R", was obtained, and the slip surface of the slope was determined. The numerical results are in good agreement with those obtained from limit equilibrium method and finite element method. It indicates that the proposed geomaterial-structure interaction algorithm works well in the GPD framework.
基金Projects(50874020, 50504005 and 50490274) supported by the National Natural Science Foundation of ChinaPorject(2007CB209407) supported by Major State Basic Research Development Program of ChinaProject(2005038250) supported by Postdoctoral Science Foundation of China
文摘Based on mesoscopic damage mechanics, numerical code RFPA2D （dynamic edition） was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The results show that the propagation phenomenon of stress wave in the surrounding rock of tunnel and the failure process of surrounding rock under explosive stress waves are reproduced realistically by using numerical code RFPA2O; from the failure process of surrounding rock, the place at which surrounding rock fractures is transferred because of tunnel reinforcing, and the rockfall and collapse caused by failure of surrounding rock are restrained by tunnel reinforcing; furthermore, the absolute values of peak values of major principal stress, and the minimal principal stress and shear stress at center point of tunnel roof are reduced because of tunnel reinforcing, and the displacement at center point of runnel roof is reduced as well, consequently the stability of tunnel increases.
基金Projects(51374257,50804060)supported by the National Natural Science Foundation of ChinaProject(NCET-09-0844)supported by the New Century Excellent Talent Foundation from MOE of China
文摘Due to the extreme complexity of mechanical response of soft surrounding rock(SR) around a tunnel under high geostatic stress conditions, the integration of physical and numerical modeling techniques was adopted. Based on the similarity theory, new composite-similar material was developed, which showed good agreement with the similarity relation and successfully simulated physico-mechanical properties(PMP) of deep buried soft rock. And the 800 mm×800 mm×200 mm physical model(PM) was conducted, in which the endoscopic camera technique was adopted to track the entire process of failure of the model all the time. The experimental results indicate that the deformation of SR around a underground cavern possessed the characteristics of development by stages and in delay, and the initial damage of SR could induce rapid failure in the later stage, and the whole process could be divided into three stages, including the localized extension of crack(the horizontal load(HL) was in the range of 130 k N to 170 k N, the vertical load(VL) was in the range of 119 k N to 153.8 k N), rapid crack coalescence(the HL was in the range of 170 k N to 210 k N, the VL was in the range of 153.8 k N to 182.5 k N) and residual strength(the HL was greater than 210 k N, the VL was greater than 182.5 k N). Under the high stress conditions, the phenomenon of deformation localization in the SR became serious and different space positions show different deformation characteristics. In order to further explore the deformation localization and progressive failure phenomenon of soft SR around the deeply buried tunnel, applying the analysis software of FLAC3 D three-dimensional explicit finite-difference method, based on the composite strain-softening model of Mohr-Coulomb shear failure and tensile failure, the calculation method of large deformation was adopted. Then, the comparative analysis between the PM experiment and numerical simulation of the three centered arch tunnels was implemented and the relationship of deformation localization and progressive failure of SR around a tunnel under high stress conditions was discussed.
基金financially supported by the National Key Basic Research Program of China (No.2010CB226805)the National Natural Science Foundation of China (Nos.51474136 and 51474013)+1 种基金the Opening Project Fund of State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology (No.MDPC2013KF06)the Research Award Fund for the Excellent Youth of Shandong University of Science and Technology (No.2011KYJQ106)
文摘In order to study the failure process of an anchorage structure and the evolution law of the body＇s defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods （DSCM）. The stress distribution of the anchorage interface was investigated using the particle flow numerical simulation method. The results indicate that there are three stages in the deformation and fail- ure process of an anchorage structure： elastic bonding stage, a de-bonding stage and a failure stage. The stress distribution in the interface controls the stability of the structure. In the elastic bonding stage, the shear stress peak point of the interface is close to the loading end, and the displacement field gradually develops into a ＂V＂ shape, in the de-bonding stage, there is a shear stress plateau in the center of the anchorage section, and shear strain localization begins to form in the deformation field. In the failure stage, the bonding of the interface fails rapidly and the shear stress peak point moves to the anchorage free end. The anchorage structure moves integrally along the macro-cracl~ The de-bonding stage is a research focus in the deformation and failure process of an anchorage structure, and plays an important guiding role in roadway support design and prediction of the stability of the surrounding rock.
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.
文摘As the non-periodic inspections are common in practice,a two-stage inspection model based on a three-stage failure process is proposed. The two-stage inspection means that the system is inspected with the first inspection interval T_1 and the second inspection interval T_2. Because of the three color schemes commonly used in industry,three stages are divided by the system lifetime:normal, minor defective and severe defective stages. Upon the failure of the system,replacement is carried out. Maintenance is done once identifying the severe defective stage. However,when the minor defective stage is identified by the second inspection interval T_2,action of halving the subsequent inspection interval is adopted.Otherwise,no action is required. Our objective function is to optimize the inspection intervals so as to minimize the expected cost per unit time. Finally,a numerical example is presented to illustrate the effectiveness of the proposed model.
文摘RFPA is a numerical testing tool for realistic failure process analysis(RFPA)of rock,concrete,composites,and engineering structures.The RFPA solution offers perfect simulation tools for robust modelling of brittle material failure and engineering structural damage.The RFPA family of 2D and 3D core products offers the full depth of analysis tools—from a conceptual simulation to advanced
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0904)the National Natural Science Foundation of China(No.42307247)。
文摘Active tectonic movements and geological disasters frequently occur in the upper reaches of the Jinsha River,increasing the likelihood of landslides obstructing the river.Taking the ancient Rongcharong landslide dam failure events in the Suwalong reach as an example,this paper first analyzes the accuracy and applicability of the commonly used methods in calculating the peak flow of the dam failure,such as the empirical formula,the numerical method based on the physical mechanism,and the computational fluid dynamics(CFD)method.Then,the peak flood flow of the Rongcharong-dammed lake when it overflows the dam is determined to be 28393-64272 m~3/s.At the same time,the failure process of landslide dam due to flood erosion was elucidated using the CFD method,which can be divided into three stages:gradual erosion in the initial stage,rapid development in the middle stage,and gradual expansion in the final stage.Finally,the factors that affect the peak flow of floods are analyzed,and suggestions for emergency treatment of landslide dams are put forward.The findings of this research can serve as a valuable reference for disaster prevention and mitigation strategies to adapt to the increasing frequency of landslide-induced river blockages.
基金funded by the National Natural Science Foundation of China(52478138).
文摘The connection efficiency of composite pre-tightened multi-tooth joint is low because of uneven load distribution and single load transmission path.In this paper,based on the principle of bio-tooth(suture)structure,combining soft material with fractal,a composite pre-tightened multi-hierarchy tooth joint is proposed,and the bearing performance and failure process of the joint through experiments and finite element method under tensile load.First,the ultimate bearing capacity,load distribution ratio,and failure process of different hierarchies of teeth joints are studied through experiments.Then,the progressive damage models of different hierarchies of tooth joints are established,and experiments verify the validity of the finite element model.Finally,the effects of soft material and increasing tooth hierarchy on the failure process and bearing capacity of composite pre-tightened tooth joints are analyzed by the finite element method.The following conclusions can be drawn:(1)The embedding of soft materials changed the failure process of the joint.Increasing the tooth hierarchy can give the joint more load transfer paths,but the failure process of the joint is complicated.(2)Embedding soft materials and increasing the tooth hierarchy simultaneously can effectively improve the bearing capacity of composite pre-tightened tooth joints,which is 87.8%higher than that of traditional three-tooth joints.
基金Funded by the National Natural Science Foundation of China(Nos.51678170,51878190)。
文摘Split Hopkinson pressure bar(SHPB)has been used to study the dynamic failure pattern of flattened mortar Brazilian disc under impact load.Each disc contains several prefabricated cracks paralleled to each other.Dynamic FEM has also been adopted to simulate such failure behavior.The mechanism of crack initiation,propagation and cut-through have been scrutinized with both experimental and numerical approaches.Influence of the number of the prefabricated cracks on the specimen strength and acoustic emission(AE)performance can be observed and studied.The results show that the strength decreases and AE counts increases,when the number of the prefabricated cracks increases.
基金This work was supported by China Scholarship Council(Grant No.202108050072)Japan Society for the Promotion of Science KAKENHI(Grant No.JP19KK0121)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection open fund(Grant No.SKLGP2018K009)。
文摘The sanding process caused by karstification in dolomite creates a special sandy dolomite stratum,where the frequent catastrophic instability of the surrounding rock occurred during tunnel construction.In this study,the micro-origin and macro-performance of the sandy dolomite stratum are first discussed.Then,a numerical model based on the coupling method between the discontinuous deformation analysis and smoothed particle hydrodynamics is proposed to depict the heterogeneous dolomite formation with different sanding degrees.Following,the mechanical behaviors of the heterogeneous dolomite samples under uniaxial compression are studied after calibrating the numerical parameters with the two single materials sampled from the tunnel site respectively.Further,the instability disasters of the dolomite surrounding rock with different sanding degrees are reproduced,and the failure behaviors of tunnels are explained with respect to the stress distribution and plastic zone.The obtained results show that the rotation and dislocation of the remained dolomite block contribute to the unsmooth stress–strain curve and deterioration in uniaxial compressive strength.However,the block serves as the skeleton in the transmission of field stress in underground space,which improves the stability of the formation.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U22A20602,U2040221).
文摘A cascading failure of landslide dams caused by strong earthquakes or torrential rains in mountainous river valleys can pose great threats to people’s lives,properties,and infrastructures.In this study,based on the three-dimensional Reynoldsaveraged Navier-Stokes equations(RANS),the renormalization group(RNG)k-εturbulence model,suspended and bed load transport equations,and the instability discriminant formula of dam breach side slope,and the explicit finite volume method(FVM),a detailed numerical simulation model for calculating the hydro-morphodynamic characteristics of cascading dam breach process has been developed.The developed numerical model can simulate the breach hydrograph and the dam breach morphology evolution during the cascading failure process of landslide dams.A model test of the breaches of two cascading landslide dams has been used as the validation case.The comparison of the calculated and measured results indicates that the breach hydrograph and the breach morphology evolution process of the upstream and downstream dams are generally consistent with each other,and the relative errors of the key breaching parameters,i.e.,the peak breach flow and the time to peak of each dam,are less than±5%.Further,the comparison of the breach hydrographs of the upstream and downstream dams shows that there is an amplification effect of the breach flood on the cascading landslide dam failures.Three key parameters,i.e.,the distance between the upstream and the downstream dams,the river channel slope,and the downstream dam height,have been used to study the flood amplification effect.The parameter sensitivity analyses show that the peak breach flow at the downstream dam decreases with increasing distance between the upstream and the downstream dams,and the downstream dam height.Further,the peak breach flow at the downstream dam first increases and then decreases with steepening of the river channel slope.When the flood caused by the upstream dam failure flows to the downstream dam,it can produce a surge wave that overtops and erodes the dam crest,resulting in a lowering of the dam crest elevation.This has an impact on the failure occurrence time and the peak breach flow of the downstream dam.The influence of the surge wave on the downstream dam failure process is related to the volume of water that overtops the dam crest and the erosion characteristics of dam material.Moreover,the cascading failure case of the Xiaogangjian and Lower Xiaogangjian landslide dams has also been used as the representative case for validating the model.In comparisons of the calculated and measured breach hydrographs and final breach morphologies,the relative errors of the key dam breaching parameters are all within±10%,which verify the rationality of the model is applicable to real-world cases.Overall,the numerical model developed in this study can provide important technical support for the risk assessment and emergency treatment of failures of cascading landslide dams.
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.
基金supported by the National Natural Science Foundation of China(71771029)
文摘A engineering system is usually repairable, and failure process of a repairable by a failure point process. The power law model is a commonly used approach to model syst the em is often described failure point process. This paper introduces the concept and model for the failure process of repairable system. The method of parameter estimation is developed, and failure observations are fitted into a power-law model by using the least square method. Two applications of the pressent model are discussed according to the practical failure data of the central cooling system of a nuclear power plant. One application is determining the optimal overhaul time, and the other is evaluating the quality of maintenance. This paper provides references for the overhaul decision making and maintenance quality evaluation in reality.
基金supported by the National Natural Science Foundation of China (No. 71671009)supported by the National Natural Science Foundation of China (No. 61573043)supported by the National Natural Science Foundation of China (No. 51675025)
文摘In this paper, a new method is developed to model dependent failure behavior among failure mechanisms. Unlike the existing methods, the developed method models the root cause of the dependency explicitly, so that a deterministic model, rather than a probabilistic one, can be established. Three steps comprise the developed method. First, physics-of-failure（PoF） models are utilized to model each failure mechanism. Then, interactions among failure mechanisms are modeled as a combination of three basic relations, competition, superposition and coupling. This is the reason why the method is referred to as ＂compositional method＂. Finally, the PoF models and the interaction model are combined to develop a deterministic model of the dependent failure behavior. As a demonstration, the method is applied on an actual spool and the developed failure behavior model is validated by a wear test. The result demonstrates that the compositional method is an effective way to model dependent failure behavior.
基金financially supported by the External Cooperation Program of Bureau of International Co-operation,Chinese Academy of Sciences(131551KYSB20130003)the Risk Evaluation and Mitigation Technology of Barrier Lake Project of China Communications Construction Company Limited(2013318J01100)+2 种基金the Key Technologies R&D Program of Sichuan Province in China(2014SZ0163)the Special Program for International S&T Cooperation projects of China(Grant No.2012DFA20980)National Natural Science Foundation of China(Grant No.51479179)
文摘Outburst floods caused by breaches of landslide dams may cause serious damages and loss of lives in downstream areas; for this reason the study of the dynamic of the process is of particular interest for hazard and risk assessment. In this paper we report a field-scale landslide dam failure experiment conducted in Nantou County, in the central of Taiwan.The seismic signal generated during the dam failure was monitored using a broadband seismometer and the signal was used to study the dam failure process.We used the short-time Fourier transform(STFT) to obtain the time–frequency characteristics of the signal and analyzed the correlation between the power spectrum density(PSD) of the signal and the water level. The results indicate that the seismic signal generated during the process consisted of three components: a low-frequency band(0–1.5 Hz), an intermediate-frequency band(1.5–10 Hz) and a highfrequency band(10–45 Hz). We obtained the characteristics of each frequency band and the variations of the signal in various stages of the landslide dam failure process. We determined the cause for the signal changes in each frequency band and its relationship with the dam failure process. The PSD sediment flux estimation model was used to interpret the causes of variations in the signal energy before the dam failure and the clockwise hysteresis during the failure. Our results show that the seismic signal reflects the physical characteristics of the landslide dam failure process. The method and equipment used in this study may be used to monitor landslide dams and providing early warnings for dam failures.
