Evolution model and failure mechanisms of rainfall-induced cracked red clay slopes:insights from Xinshao County,China

Red clay landslides are widely distributed worldwide,resulting in severe loss of life and property.Although rainfall-induced red clay slopes have received extensive attention,the role of cracks in the evolutionary process of red clay slopes and their connection to failure mechanisms is still poorly understood.A comprehensive approach integrating field investigation,laboratory tests,and numerical simulations was conducted to study the 168 red clay landslides in Xinshao County,China.The results show that red clay is prone to forming cracks at high moisture content due to its low swelling and high shrinkage properties.The failure mode of red clay slopes can be summarized in three stages:crack generation,slope excavation,and slope failure.Furthermore,the retrospective analysis and numerical simulations of the typical landslide in Guanchong indicated that intense rainfall primarily impacts the shallow layer of soil within approximately 0.5 m on the intact slope.However,cracks change the pattern of rainfall infiltration in the slope.Rainwater infiltrates rapidly through the preferential channels induced by the cracks rather than uniformly and slowly from the slope surface.This results in a significant increase in both the depth of infiltration and the saturated zone area of the cracked slope,reaching 3.8 m and 36.2 m^(2),respectively.Consequently,the factor of safety of the slope decreases by 13.4%compared to the intact slope,ultimately triggering landslides.This study can provide valuable insights into understanding the failure mechanisms of red clay slopes in China and other regions with similar geological settings.

Experimental studies on rock failure mechanisms under impact load by single polycrystalline diamond compact cutter

Percussive drilling shows excellent potential for promoting the rate of penetration(ROP)in drilling hard formations.Polycrystalline diamond compact(PDC)bits account for most of the footage drilled in the oil and gas fields.To reveal the rock failure mechanisms under the impact load by PDC bits,a series of drop tests with a single PDC cutter were conducted to four kinds of rocks at different back rake angles,drop heights,drop mass,and drop times.Then the morphology characteristics of the craters were obtained and quantified by using a three-dimensional profilometer.The fracture micrographs can be observed by using scanning electron microscope(SEM).The distribution and propagation process of subsurface cracks were captured in rock-like silica glass by a high-speed photography system.The results can indicate that percussive drilling has a higher efficiency and ROP when the rock fractures in brittle mode.The failure mode of rock is related with the type of rock,the impact speed,and the back rake angle of the cutter.Both the penetration depth and fragmentation volume get the maximum values at a back rake angle of about 45°.Increasing the weight and speed of falling hammer is beneficial to improving the rock breaking effects and efficiency.The subsurface cracks under the impact load by a single PDC cutter is shaped like a clamshell,and its size is much larger than the crater volume.These findings can help to shed light on the rock failure mechanisms under the impact of load by a single PDC cutter and provide a theoretical explanation for better field application of percussive drilling.

Numerical and experimental analyses of rock failure mechanisms due to microwave treatment

Despite the extensive studies conducted on the effectiveness of microwave treatment as a novel rock preconditioning method,there is yet to find reliable data on the rock failure mechanisms due to microwave heating.In addition,there is no significant discussion on the energy efficiency of the method as one of the important factors among the mining and geotechnical engineers in the industry.This study presents a novel experimental method to evaluate two main rock failure mechanisms due to microwave treatment without applying any mechanical forces,i.e.distributed and concentrated heating.The result shows that the existence of a small and concentrated fraction of a strong microwave absorbing mineral will change the failure mechanism from the distributed heating to the concentrated heating,which can increase the weakening over microwave efficiency(WOME)by more than 10 folds.This observation is further investigated using the developed coupled numerical model.It is shown that at the same input energy,the existence of microwave absorbing minerals can cause major heat concentration inside the rock and increase the maximum temperature by up to three times.

Numerical modeling of failure mechanisms in phyllite mine slopes in Brazil

This paper presents three case studies comprising failure mechanisms in phyllite mine slopes at Quadrila- tero Ferrifero, State of Minas Gerais, Brazil. Numerical modeling techniques were used in this study. Fail- ure mechanisms involving discontinuities sub parallel to the main foliation are very common in these mines. Besides, failure through the rock material has also been observed due to the low strength of phyl- lites in this site. Results of this work permitted to establish unknown geotechnical parameters which have significant influence in failure processes, like the in situ stress field and the discontinuity stiffness.

Characterization of Failure Mechanisms of Duplex and Graded Thermal Barrier Coatings Exposed to Thermal Shock Test

The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.

Seismic failure mechanisms for loaded slopes with associated and nonassociated flow rules

Seismic failure mechanisms were investigated for soil slopes subjected to strip load with upper bound method of limit analysis and finite difference method of numerical simulation,considering the influence of associated and nonassociated flow rules.Quasi-static representation of soil inertia effects using a seismic coefficient concept was adopted for seismic failure analysis.Numerical study was conducted to investigate the influences of dilative angle and earthquake on the seismic failure mechanisms for the loaded slope,and the failure mechanisms for different dilation angles were compared.The results show that dilation angle has influences on the seismic failure surfaces,that seismic maximum displacement vector decreases as the dilation angle increases,and that seismic maximum shear strain rate decreases as the dilation angle increases.

Dynamic tensile strength and failure mechanisms of thermally treated sandstone under dry and water-saturated conditions

To study the tensile strength and failure mechanisms of rock with hydro-thermal coupling damage under different loading rates,a series of static and dynamic splitting tests were conducted on thermally treated sandstone under dry and water-saturated conditions.Experimental results showed that high temperatures effectively weakened the tensile strength of sandstone specimens,and the P-wave velocity declined with increasing temperature.Overall,thermal damage of rock increased gradually with increasing temperature,but obvious negative damage appeared at the temperature of 100℃.The water-saturated sandstone specimens had lower indirect tensile strength than the dry ones,which indicated that water-rock interaction led to secondary damage in heat-treated rock.Under both dry and water-saturated conditions,the dynamic tensile strength of sandstone increased with the increase of strain rate.The water-saturated rock specimens showed stronger rate dependence than the dry ones,but the loading rate sensitivity of thermally treated rock decreased with increasing treatment temperature.With the help of scanning electron microscopy technology,the thermal fractures of rock,caused by extreme temperature,were analyzed.Hydro-physical mechanisms of sandstone under different loading rate conditions after heat treatment were further discussed.

Comprehensive analyses of initiation and failure mechanisms of the 2017 Xinmo catastrophic rockslide

The failure of the 2017 Xinmo catastrophic rockslide in Maoxian County, Sichuan, Southwest China was a combined effect of long-term and shortterm triggering factors. Field investigation, historical data collection, laboratory tests, chemical and microstructure analysis and numerical simulations were adopted herein to reveal the initiation and failure mechanism of the Xinmo rockslide. The analytical results showed that this failure involved the coupling of several triggering factors. The initial cracks in the rock mass were induced by historical earthquakes due to the convex topography and the direction effect. Rock masses from the source area of the Xinmo rockslide contain water-sensitive minerals, i.e., albite and chamosite, and the easily oxidized chemical element Fe, resulting in obvious strength deterioration under the action of water. The scanning electron microscopy(SEM) experimental results indicated that the internal structure of the rock mass is conducive to weathering. The compressive and shear strengths of the rock mass were reduced due to freeze-thaw cycles and weathering. The antecedent rainfall further deteriorated the stability of the slope, and stress and deformation accumulated continually in the locked section. Finally, the locked section sheared out, and the slope failed. An entrainment effect was observed in the Xinmo rockslide due to the presence of old landslide deposits and the antecedent rainfall, resulting in an amplification of the catastrophic rockslide. A simplified three dimensional analysis model was established in this study to reveal the influence of the triggering factors on the failure mechanism of the Xinmo rockslide.

Research progress in failure mechanisms and electrolyte modification of high-voltage nickel-rich layered oxide-based lithium metal batteries

High-voltage nickel(Ni)-rich layered oxide-based lithium metal batteries(LMBs)exhibit a great potential in advanced batteries due to the ultra-high energy density.However,it is still necessary to deal with the challenges in poor cyclic and thermal stability before realizing practical application where cycling life is considered.Among many improved strategies,mechanical and chemical stability for the electrode electrolyte interface plays a key role in addressing these challenges.Therefore,extensive effort has been made to address the challenges of electrode-electrolyte interface.In this progress,the failure mechanism of Ni-rich cathode,lithium metal anode and electrolytes are reviewed,and the latest breakthrough in stabilizing electrode-electrolyte interface is also summarized.Finally,the challenges and future research directions of Ni-rich LMBs are put forward.

Failure mechanisms in flexible electronics

The rapid evolution of flexible electronic devices promises to revolutionize numerous fields by expanding the applications of smart devices.Nevertheless,despite this vast potential,the reliability of these innovative devices currently falls short,especially in light of demanding operation environment and the intrinsic challenges associated with their fabrication techniques.The heterogeneity in these processes and environments gives rise to unique failure modes throughout the devices'lifespan.To significantly enhance the reliability of these devices and assure long-term performance,it is paramount to comprehend the underpinning failure mechanisms thoroughly,thereby,enabling,optimal design solutions.A myriad of investigative efforts have been dedicated to unravel these failure mechanisms,utilizing a spectrum of tools from analytical models,numerical methods,to advanced characterization methods.This review delves into the root causes of device failure,scrutinizing both the fabrication process and the operation environment.Next,We subsequently address the failure mechanisms across four commonly observed modes:strength failure,fatigue failure,interfacial failure,and electrical failure,followed by an overview of targeted characterization methods associated with each mechanism.Concluding with an outlook,we spotlight ongoing challenges and promising directions for future research in our pursuit of highly resilient flexible electronic devices.

Comparative study on microstructure evolution and failure mechanisms of ordinary and refurbished EB-PVD TBC under cyclic oxidation

Refurbishment of thermal barrier coating(TBC)has become a valuable technique to prolong the service life of high-temperature components.This study investigates the effect of the refurbishment process(coating removal and recoating)on the microstructure evolution and physical properties of TBC,including oxidation characteristics,element diffusion behavior,and crack failure mechanisms.The results showed that a certain amount of interdiffusion zone(IDZ)with Cr-rich would be retained in DD6 superalloy substrate after coating removal.The microstructure of the refurbished specimens showed equiaxedβ-NiAl phases,while the ordinary specimens have elongated grain shapes with a high aspect ratio.Moreover,mixed oxides in the refurbished TBC specimens were earlier observed during cyclic oxidation,with a greater thickness compared to ordinary TBC,due to the influence of BC layer phase sizes.The growth mechanism of thermally grown oxide(TGO-Al_(2)O_(3)layer)in the refurbished TBC specimens was also different,resulting from the different mechanisms of mixed oxides growth.Furthermore,under cyclic oxidation with water quenching at 1100℃,the cracks in the refurbished specimen tend to occur in the mixed oxides layer,while the cracks in the ordinary specimen occur in the top coat(TC)layer,attributing to the earlier and thicker mixed oxides layer formed in refurbished specimens.

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.

Failure mechanism and infrared radiation characteristic of hard siltstone induced by stratification effect

The deformation in sedimentary rock induced by train loads has potential threat to the safe operation of tunnels. This study investigated the influence of stratification structure on the infrared radiation and temporal damage mechanism of hard siltstone. The uniaxial compression tests, coupled with acoustic emission(AE) and infrared radiation temperature(IRT) were conducted on siltstones with different stratification effects. The results revealed that the stratigraphic structure significantly affects the stress-strain response and strength degradation characteristics. The mechanical parameters exhibit anisotropy characteristics, and the stratification effect exhibits a negative correlation with the cracking stress and peak stress. The failure modes caused by the stratification effect show remarkable anisotropic features, including splitting failure(Ⅰ: 0°-22.50°, Ⅱ: 90°), composite failure(45°), and shearing failure(67.50°). The AE temporal sequences demonstrate a stepwise response characteristic to the loading stress level. The AE intensity indicates that the stress sensitivity of shearing failure and composite failure is generally greater than that of splitting failure. The IRT field has spatiotemporal migration and progressive dissimilation with stress loading and its dissimilation degree increases under higher stress levels. The stronger the stratification effect, the greater the dissimilation degree of the IRT field. The abnormal characteristic points of average infrared radiation temperature(AIRT) variance at local stress drop and peak stress can be used as early and late precursors to identify fracture instability. Theoretical analysis shows that the competitive relationship between compaction strengthening and fracturing damage intensifies the dissimilation of the infrared thermal field for an increasing stress level. The present study provides a theoretical reference for disaster warnings in hard sedimentary rock mass.

Failure behavior and strength model of blocky rock mass with and without rockbolts

To better understand the failure behaviours and strength of bolt-reinforced blocky rocks,large scale extensive laboratory experiments are carried out on blocky rock-like specimens with and without rockbolt reinforcement.The results show that both shear failure and tensile failure along joint surfaces are observed but the shear failure is a main controlling factor for the peak strength of the rock mass with and without rockbolts.The rockbolts are necked and shear deformation simultaneously happens in bolt reinforced rock specimens.As the joint dip angle increases,the joint shear failure becomes more dominant.The number of rockbolts has a significant impact on the peak strain and uniaxial compressive strength(UCS),but little influence on the deformation modulus of the rock mass.Using the Winkler beam model to represent the rockbolt behaviours,an analytical model for the prediction of the strength of boltreinforced blocky rocks is proposed.Good agreement between the UCS values predicted by proposed model and obtained from experiments suggest an encouraging performance of the proposed model.In addition,the performance of the proposed model is further assessed using published results in the literature,indicating the proposed model can be used effectively in the prediction of UCS of bolt-reinforced blocky rocks.

Ground response and failure mechanism of gob-side entry by roof cutting with hard main roof

This study is the result of long-term efforts of the authors’team to assess ground response of gob-side entry by roof cutting(GSERC)with hard main roof,aiming at scientific control for GSERC deformation.A comprehensive field measurement program was conducted to determine entry deformation,roof fracture zone,and anchor bolt(cable)loading.The results indicate that GSERC deformation presents asymmetric characteristics.The maximum convergence near roof cutting side is 458 mm during the primary use process and 1120 mm during the secondary reuse process.The entry deformation is closely associated with the primary development stage,primary use stage,and secondary reuse stage.The key block movement of roof cutting structure,a complex stress environment,and a mismatch in the supporting design scheme are the failure mechanism of GSERC.A controlling ideology for mining states,including regional and stage divisions,was proposed.Both dynamic and permanent support schemes have been implemented in the field.Engineering practice results indicate that the new support scheme can efficiently ensure long-term entry safety and could be a reliable approach for other engineering practices.

Recent advances in quantifying the inactive lithium and failure mechanism of Li anodes in rechargeable lithium metal batteries

Lithium metal is considered as the ultimate anode material for the next generation of high-energy density batteries.However,non-uniform lithium dendrite growth,serious electrolyte consumption,and significant volume changes during lithium deposition/stripping processes lead to sustained accumulation of inactive lithium and poor cycling reversibility.Quantifying the formation and evolution of inactive lithium under different conditions and fully evaluating the complex failure modes are the key issues in this challenging field.This article comprehensively reviews recent research progress on the quantification of formation and evolution of inactive lithium detected by different quantitative techniques in rechargeable lithium metal batteries.The key research challenges such as failure mechanism,modification strategies and operando characterization of lithium metal anodes are systematically summarized and prospected.This review provides a new angle of view to understand failure mechanism of lithium metal anodes and inspiration and guidance for the future development of rechargeable lithium metal batteries.

Knowledge representation and decoupling analysis on failure mechanisms of remotely controlled intelligent machinery

Remotely controlled intelligent machinery has complications,including loose manage-ment of failure information,low information availability,and coupling influence among systems,which can be effectively solved by analyzing the system state and information characteristics of the equipment.Taking intelligent agricultural machinery as the object,this study applies the knowledge representation method to explore equipment failure states’informational features and construct a knowledge framework model of system fail-ure representation relations and a complex network conceptual model to visualize the fail-ure information more intuitively and facilitate systematic management and utilization.The feedback-based decoupling analysis method uncouples the coupling between subsys-tems,identifying the critical state of decoupling well.It attempts to apply the knowledge representation and decoupling analysis to remotely controlled intelligent agricultural machinery equipment.Through the example,the result further illustrates the feasibility of knowledge representation and decoupling for remotely controlled intelligent agricultural machinery systems and provides essential support for better failure analysis.

Reliability evaluation of avionics system with imperfect fault coverage and propagated failure mechanisms

Fault tolerance designs are essential techniques for systems that require high levels of reliability,such as aircraft or spacecraft control system.Imperfect Fault Coverage(IFC)may lead to the failure of a system or subsystem even with adequate redundancy.Previous studies of IFC mostly concentrated on evaluating Coverage Factor(CF),whereas the system failure behaviors with IFC have rarely been involved.Failures that occur in low-layer may be covered by highlayer.However,if the coverage is imperfect,uncovered failure will have functional and physical impact on the system behavior.In this thesis,the failure behavior and reliability of IFC of multi-layer systems are studied and a Binary Decision Diagram(BDD)-based modeling and simulation method are proposed to evaluate system reliability.As a case,the failure behavior of an aero engine electronic controller with IFC is studied.The results show that the IFC may impact system behavior without taking the IFC into account,the system maintenance intervals may reduce,and thus the maintenance costs will increase.

Spatial distribution and failure mechanism of water-induced landslides in the reservoir areas of Southwest China

Water-induced landslides in hydropower reservoirs pose a great threat to both project operation and human life.This paper examines three large reservoirs in Sichuan Province,China.Field surveys,site monitoring data analyses and numerical simulations are used to analyze the spatial distribution and failure mechanisms of water-induced landslides in reservoir areas.First,the general rules of landslide development in the reservoir area are summarized.The first rule is that most of the landslides have rear edge elevations of 100e500 m above the normal water level of the reservoir,with volumes in the range of 106 e107 m 3.When the volume exceeds a certain amount,the number of sites at which the landscape can withstand landslides is greatly reduced.Landslide hazards mainly occur in the middle section of the reservoir and less in the annex of the dam site and the latter half of the reservoir area.The second rule is that sedimentary rocks such as sandstone are more prone to landslide hazards than other lithologies.Then,the failure mechanism of changes in the water level that reduces the stability of the slope composed of different geomaterials is analyzed by a proposed slope stability framework that considers displacement and is discussed with the monitoring results.Permeability is an essential parameter for understanding the diametrically opposed deformation behavior of landslides experiencing filling-drawdown cycles during operation.This study seeks to provide inspiration to subsequent researchers,as well as guidance to technicians,on landslide prevention and control in reservoir areas.

Deformation and failure mechanism of Yanjiao rock slope influenced by rainfall and water level fluctuation of the Xiluodu hydropower station reservoir

With the construction of the Xiluodu hydropower station on the Jinsha River,the reservoir impoundment began in 2013 and the water level fluctuates annually between 540 m and 600 m above sea level.The Yanjiao rock slope which is located on the left bank of the Jinsha River 75 km upstream of the Xiluodu dam site,began to deform in 2014.The potential failure of the slope not only threatens Yanjiao town but also affects the safe operation of the Xiluodu reservoir.This paper is to find the factors influencing the Yanjiao slope deformation through field investigation,geotechnical reconnaissance,and monitoring.Results show that the Yanjiao slope can be divided into a bank collapse area(BCA)and a strong deformation area(SDA)based on the crack distribution characteristics of the slope.The rear area of the slope has been experiencing persistent deformation with a maximum cumulative displacement(GPS monitoring point G4)of 505 mm and 399 mm in the horizontal and vertical directions,respectively.The potential failure surface of the slope is formed 36 m below the surface based on the borehole inclinometer.The bank collapses of the Yanjiao slope are directly caused by the reservoir impoundment while the deformation area of the slope is affected by the combination of the rainfall and reservoir water level fluctuation.Based on mechanism of the Yanjiao slope,prestressed anchor combined with the surface drainage and slope unloading are recommended to prevent potential deformation.