Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study invest...Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study investigates their coupled effects using inclinedflume experiments and Discrete Element Method(DEM)simulations,covering three gravel sizes(2-5 mm,5-7 mm,7-10 mm)and four ice-content levels(0%,20%,40%,60%).Run-out distance,velocity,energy components,flow regime(Savage number),and segregation indexαwere quantified.Increasing ice content significantly enhances mobility,but with diminishing marginal effectiveness.From 0%to 40%ice content,run-out distance increases by 41%-86%,whereas the additional increase from 40%to 60%contributes only 12%-23%.Particle-size ratio strongly governs segregation intensity.Fine-gravel groups reach segregation indices ofα=0.92-0.98,indicating nearly complete upward migration of ice,whereas medium-gravel and coarse-gravel groups exhibit much weaker segregation,stabilizing atα=0.68-0.74 and 0.60-0.69.Savage number analyses reveal marked flow-regime transitions.At 0%ice content,Savage numbers reach 1.0-1.5,indicating a collisional regime.Increasing ice content suppresses collisionality,with Savage numbers decreasing to 0.03-0.07 at 60%ice content,consistent with dense-regime flow.DEM energy analyses confirm this regime shift:for finegravel mixtures,collision energy decreases by 14%,while sliding-friction energy increases by 33%as ice content increases from 0%to 60%,reflecting enhanced overburden effects imposed by upward-segregated ice layers.Medium and coarse mixtures exhibit weaker or opposite energy-shift patterns,demonstrating strong size dependence.Mechanistically,large particle-size contrasts promote strong segregation and form dense basal rock layers that increase basal friction and reduce mobility.When particle sizes are similar or ice content is high,segregation remains limited,allowing ice to mix into the basal layer,thereby reducing basal friction and enhancing mobility.This research quantitatively demonstrates how composition controls particle spatial distribution,flow regime,and energy dissipation,offering new mechanistic insights into the propagation and deposition behaviors of rock-ice avalanches and improving hazard assessment in vulnerable high-mountain regions.展开更多
In this paper,a comprehensive evaluation on the silicon/silicon carbide(Si/SiC)hybrid switch is performed through experimental tests in terms of both electrical performance and robustness under extreme stresses.Based ...In this paper,a comprehensive evaluation on the silicon/silicon carbide(Si/SiC)hybrid switch is performed through experimental tests in terms of both electrical performance and robustness under extreme stresses.Based on the optional turn-on and turn-off delay times under the efficiency control mode obtained from the double-pulse test(DPT),both nondestructive and destructive single-pulse avalanche tests are conducted on the Si/SiC hybrid switch as well as on the two discrete device branches inside the hybrid switch.In addition,the avalanche voltage,critical avalanche energy,and peak avalanche current,which intrinsically characterize the unclamped-inductive-switching(UIS)avalanche characteristics,are carefully examined.In this way,the physical factors dominating the UIS characteristics of the hybrid switch,thus limiting its single-pulse avalanche withstand capability,are specifically and comprehensively identified;the underlying physical mechanisms are analyzed and revealed in depth,and how the gate control sequence affects the UIS characteristics of the hybrid switch is extensively investigated.We additionally carry out short-circuit(SC)tests under the fault-under-load(FUL)condition and perform a parallel in-depth analysis to experimentally determine which branch dominates the SC withstand capability of the hybrid switch.Our experimental study indicates that,for both SC robustness and single-pulse avalanche capability,the limiting factor is a single device branch among the two parallel discrete devices,and the UIS behavior is sensitive to the variation of the gate turn-off delay time Toff_delay.The study conducted in this paper not only provides deep academic insights into the electrical performance and reliability of the Si/SiC hybrid switch,but also offers fundamental theoretical principles and technical evidence to support its more efficient and long-term reliable applications of the hybrid switch in the industrial fields.展开更多
A 32-channel charge-sensitive amplifier(CSA)is designed for fast timing in the delay-line readout of a parallel plate avalanche counter(PPAC)array.It is realized on a PCB with operational amplifiers and other discrete...A 32-channel charge-sensitive amplifier(CSA)is designed for fast timing in the delay-line readout of a parallel plate avalanche counter(PPAC)array.It is realized on a PCB with operational amplifiers and other discrete components.Each channel consists of an integrator,a pole-zero cancellation net,and a linear amplification stage,which can be adapted to accommodate either positive or negative input signals.The RMS equivalent input noise charges are 3.3 fC,the conversion gains are approximately±2 mV∕fC,and the intrinsic time resolution reaches 32 ps.In the prototype PPAC application,the CSA performs as well as the commercial FTA820A amplifier,providing a position resolution as good as 0.17 mm,and exhibiting reliable stability during several hours of continuous data acquisition.展开更多
The dynamic avalanche effect is a critical factor influencing the performance and reliability of the field-stop insulated gate bipolar transistors(FS-IGBT).Unclamped inductive switching(UIS)is the primary method for t...The dynamic avalanche effect is a critical factor influencing the performance and reliability of the field-stop insulated gate bipolar transistors(FS-IGBT).Unclamped inductive switching(UIS)is the primary method for testing the dynamic avalanche capability of FS-IGBTs.Numerous studies have demonstrated that factors such as device structure,avalanche-generating current filaments,and electrical parameters influence the dynamic avalanche effect of the FS-IGBT.However,few studies have focused on enhancing the avalanche reliability of the FS-IGBT by adjusting circuit parameters during operation.In this paper,the dynamic avalanche effect of the FS-IGBT under UIS conditions is comprehensively investigated through a series of comparative experiments with varying circuit parameters,including bus voltage V_(DC),gate voltage V_(G),gate resistance R_(g),load inductance L,and temperature TC.Furthermore,a method to enhance the dynamic avalanche reliability of the FS-IGBT under UIS by optimizing circuit parameters is proposed.In practical applications,reducing gate voltage,increasing load inductance,and lowering temperature can effectively improve the dynamic avalanche capability of the FS-IGBT.展开更多
This study represents a pioneering effort to analyze the impact of avalanches descending into Morskie Oko from Marchwiczny Gully,the most active avalanche path around the lake.It focuses on catastrophic avalanches tha...This study represents a pioneering effort to analyze the impact of avalanches descending into Morskie Oko from Marchwiczny Gully,the most active avalanche path around the lake.It focuses on catastrophic avalanches that descended from the analyzed gully,as reported in the literature from the 1900s until now.However,only the data collected in recent years,our field studies,combined with modern LIDAR data and GIS-based modeling,allowed us to perform a detailed analysis.The GIS-based approach effectively uses spatial data to address snow avalanche modeling challenges.Although the study area lies within Tatra National Park,no official services carry out systematic avalanche monitoring or measurements.The impact of hazardous events,such as snow avalanches,on the most famous Polish mountain lake,Morskie Oko,has been poorly described in the literature and has yet to be discovered.Therefore,to analyze the selected avalanche parameters,we mainly used our ground and additional aerial photographs taken by local mountain services and related field measurements.Our analysis resulted in figurative estimates of the extent and volume of avalanche snow and its weight,both on the surface of the ice sheet and the part of the avalanche that did not reach the lake's shore and remained on the slope of Marchwiczny Gully.For example,the values for the mighty avalanche on February 3,2023,are 23,500 m~3 and 4,700 tons on the ice surface and 20,000 m~3 and 4,000 tons on the slope.It was determined that avalanches that descend onto the studied lake's surface result in its shallowing.This process occurs because of sedimentation of slope material carried by avalanches,especially during the final phase of ice cover melting.When openings appear in the solid ice cover in spring,floating ice can migrate,driven by wind pressure,and deposit avalanche material in various parts of the lake bottom.Thus,avalanches contributed to the gradual disappearance of the lake.展开更多
Snow avalanches present a significant threat to infrastructure,affecting buildings,roads,railways,and power lines,and frequently leading to massive economic losses in livelihoods and production.With the increase in re...Snow avalanches present a significant threat to infrastructure,affecting buildings,roads,railways,and power lines,and frequently leading to massive economic losses in livelihoods and production.With the increase in regional temperatures and the occurrence of extreme snowfall events,the frequency and intensity of avalanches have escalated,resulting in more severe incidents and higher casualty rates.As natural archives of environmental changes,tree rings offer valuable proxies for avalanche hazard assessments in regions where direct observation data is scarce,particularly in high-altitude regions.The dendrogeomorphology has been gradually being applied in avalanche hazard evaluation,however,it remains limited in China.To address this gap,this study systematically investigates the principles and methodologies for reconstructing avalanche histories and evaluates their applications in avalanche hazard assessments through a literature review and field observations.It provides a comprehensive overview of recent advancements in key areas,including the impact of avalanches on forest ecosystems,the reconstruction of avalanches,and the analysis of avalanche events(i.e.,the spatiotemporal distribution,the historical recurrence intervals,magnitudes,and triggering conditions of avalanches).Considering the current limitations in avalanche hazard assessments and the urgent need for such research in China,we outline key priorities and future directions,including refining reconstruction methodologies,developing a comprehensive tree-ring-based avalanche database for high-altitude regions,and establishing an advanced hazard assessment framework based on dendrochronological evidence.展开更多
The impact of cross-sectional topographic variability on the kinetic properties of granular flows has been underexplored,which hinders the understanding of the kinematics of rock avalanches.In this study,the throat co...The impact of cross-sectional topographic variability on the kinetic properties of granular flows has been underexplored,which hinders the understanding of the kinematics of rock avalanches.In this study,the throat contraction index(T)is introduced to quantify variations in throat topography,and 96 numerical simulation experiments with varying T and slope angles(δ)are conducted.The findings indicate that granular flows experience transient obstructions when traversing throat topographies,primarily due to the periodic formation and breaking of the arch structure.Observations suggest that the acceleration of velocity in the tails of granular flows is restrained by the throat region,potentially altering the dynamics of related geohazards.In this study,the impact of throat topography is quantitatively assessed,demonstrating a reduction in peak flowrates of granular materials by 20%-80% and extending the flowduration up to six times.The present study proposes the throat-induced hazard index(Φ)to evaluate the influenceof throat topography on the risk of rockslides and avalanches characterized by granular flows,which may provide insights for the design of mitigation structures in topographic regions.展开更多
Air blasts induced by rock-ice avalanches are common natural phenomena known for their far-field destructive impact.In this study,remote sensing images,eyewitness videos and numerical modelling were comprehensively ap...Air blasts induced by rock-ice avalanches are common natural phenomena known for their far-field destructive impact.In this study,remote sensing images,eyewitness videos and numerical modelling were comprehensively applied to analyze the initiation and propagation of the 2021 Chamoli avalancheinduced air blast.Our findings indicate that air blasts are observed from the avalanche source area to the Rishiganga valley,but nearly disappear in the Dhauliganga valley.The most intense air blast is concentrated on the left side of Ronti Gad valley,with maximum velocity and pressure estimated at over 70 m/s and 20 kPa,respectively.Such high pressure results in widespread tree breakage in the area.Based on the analysis of the Chamoli event,we further discussed the potential contribution of the avalanche flow regime,avalanche dynamics and geomorphology to the destructive potential of air blasts.Rapidly moved sliding mass can impart the air blast a high initial momentum,and this process will be exaggerated when the avalanche impacts valley walls at bends.However,when the rock-ice avalanche transforms into a debris-enriched flash flood,free water within the flowing mass can displace air,inhibiting the generation of air blasts.Our work offers new insights into the generation and propagation of rock-ice avalanche-induced air blasts,underscoring the importance of including this type of hazard during avalanche risk assessment in high-altitude glacial regions.展开更多
Massive granitic rock avalanches are extensively developed in the middle section of the northern Qinling Mountains(NQM),China.The current consensus is that their formation could have been connected with seismic events...Massive granitic rock avalanches are extensively developed in the middle section of the northern Qinling Mountains(NQM),China.The current consensus is that their formation could have been connected with seismic events that occurred in the NQM.However,there is a lack of systematic discussion on the genetic dynamics of these rock avalanches.Hence,taking Earth system scientific research as a starting point,this paper systematically summarizes and discusses development characteristics,formation times and genetic dynamic mechanisms of granitic rock avalanches in the NQM based on geological investigations,high-precision remote sensing interpretations,geomorphological dating,geophysical exploration,and a large-scale shaking table model test.We identified 53 granitic rock avalanches in this area,with a single collapse area ranging from 0.01×10~6 to 1.71×10~6 m^(2).Their development time can be divided into six stages,namely,107000 years BP,11870–11950 years BP,11000 years BP,2300 years BP,1800 years BP,and 1500 years BP,which were closely related to multiple prehistoric or ancient earthquakes.We suggest that long-term coupling of internal and external earth dynamics was responsible for the granitic rock avalanches in the NQM;the internal dynamics were mainly related to subduction,collision and extrusion of different plates under the Qinling terrane,leading to the formation and tectonic uplift of the Qinling orogenic belt;and the external dynamics were closely associated with climate changes resulting in mountain denudation,freeze-thaw cycles and isostatic balance uplift.In this process,the formation and evolution of the Qinling orogenic belt play a geohazard-pregnant role,structural planes,including faults and joints,play a geohazard-controlled role,and earthquakes play a geohazard-induced role,which jointly results in the occurrence of large-scale granitic rock avalanches in the NQM.This research can not only decipher the genetic dynamic mechanism of large hard granitic rock avalanches but also reveal temporal and spatial patterns of the evolution of breeding and the generation of large-scale rock avalanches in the margins of orogenic belts.展开更多
In this study,avalanches in the Aerxiangou section of the Duku Expressway in the Tianshan Mountain area of Xinjiang were taken as the research object,and 92 avalanches were accurately identified through onsite researc...In this study,avalanches in the Aerxiangou section of the Duku Expressway in the Tianshan Mountain area of Xinjiang were taken as the research object,and 92 avalanches were accurately identified through onsite research.A high-resolution three-dimensional model was established by collecting images from unmanned aerial vehicles for an in-depth understanding of the avalanche danger of the region,according to the sample set selection of different uses of machine learning support vector machines to establish the S1-RBFKSVM,S1-PKSVM,S2-RBFKSVM,and S2-PKSVM avalanche susceptibility coupling models.On the basis of the avalanche point susceptibility,the impact velocity,impact force,avalanche volume,and throw distance constitute the hazard evaluation system.The study results revealed that slopes in the range of 26.6°–46.9°are more prone to avalanches,and sample set 2 improved the accuracy by approximately 30%compared with sample set 1 trained in the avalanche susceptibility model.Principal component analysis revealed a total of 16 high-risk avalanches,which were distributed mainly on the southern side of the route.This study provides data support for avalanche simulations as well as early warning and prevention and provides theoretical and methodological guidance for the construction and operation of the Duku Expressway.展开更多
Large-scale ice avalanches pose serious risks owing to their high speed and long travel distances,and their mobility is increased by ice melting owing to frictional heat.Most motion models for largescale ice avalanche...Large-scale ice avalanches pose serious risks owing to their high speed and long travel distances,and their mobility is increased by ice melting owing to frictional heat.Most motion models for largescale ice avalanches have been constructed for specific scenarios,neglecting the key effect of frictional ice melting on their mobility and having limited applicability.In this study,a two-dimensional model combining thermodynamic and dynamic properties was proposed.This model,based on depth-averaged and granular flow theories,considers the friction weakening process to simulate the dynamics of ice avalanches.The governing equations for motion and heat transfer were solved by employing the finite volume and the Crank-Nicolson methods.The numerical simulation results showed that the friction weakening caused by the thermal effect on the sliding surface significantly reduced the friction coefficient between the ice mass and its substrate,increasing the travel distance of ice avalanches.The initial ice content in the shear band affects the friction coefficient during the viscous and Coulomb friction stages.The higher the initial ice content in the shear band,the lower the viscous resistance during the frictional heatinginduced drag reduction stage,resulting in a longer sliding distance and larger coverage area.Notably,large-scale ice avalanches exhibit a"Volume Effect"similar to other mass movements such as landslides,debris flows,and rock avalanches.Ice avalanches with larger volumes exhibit greater mobility and coverage areas.The proposed model reveals the dynamic characteristics of large-scale ice avalanches under the effect of frictional heat and offers a valuable tool for dynamic analysis and supporting disaster risk reduction strategies.展开更多
Debris avalanches are a major concern due to their high mobility.However,the mechanism of friction weakening in debris avalanches remains poorly understood.This study systematically investigates the friction weakening...Debris avalanches are a major concern due to their high mobility.However,the mechanism of friction weakening in debris avalanches remains poorly understood.This study systematically investigates the friction weakening mechanism of granular flows using rotation drum experiments,large-scale chute experiments,and numerical simulations.Notably,dilation of granular flows is a characteristic feature associated with friction weakening.The results indicate that dilation occurs synchronously with friction weakening during the motion of granular flows,as evidenced by the motion patterns and force interactions of debris avalanches.Collision contacts were identified as the primary driver of particle dilation.An optimal collision strength can induce dilation of granular flows,reducing contact between the sliding body and substrate,thereby leading to friction weakening.The peak collision strength of granular flows during movement is determined by fragment size.The critical condition for triggering friction weakening in debris avalanches is identified as the peak Savage number(Ns,p)greater than 1.06.A mathematical model based on the granular inertial collision-friction coupling equation was developed.This study provides compelling evidence that the fractal dimension of various types of high-speed debris avalanches tends to stabilize within a narrow range.展开更多
A near-infrared single-photon detection system is established by using pigtailed InGaAs/InP avalanche photodiodes. With a 50GHz digital sampling oscilloscope, the function and process of gated-mode （Geiger-mode） sin...A near-infrared single-photon detection system is established by using pigtailed InGaAs/InP avalanche photodiodes. With a 50GHz digital sampling oscilloscope, the function and process of gated-mode （Geiger-mode） single-photon detection are intuitionally demonstrated for the first time. The performance of the detector as a gated-mode single-photon counter at wavelengths of 1310 and 1550nm is investigated. At the operation temperature of 203K,a quantum efficiency of 52% with a dark count probability per gate of 2.4 × 10 ^-3 ,and a gate pulse repetition rate of 50kHz are obtained at 1550nm. The corresponding parameters are 43%, 8.5 × 10^-3 , and 200kHz at 238K.展开更多
基金funded by the Natural Science Foundation of China(Grants No 42277127)。
文摘Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study investigates their coupled effects using inclinedflume experiments and Discrete Element Method(DEM)simulations,covering three gravel sizes(2-5 mm,5-7 mm,7-10 mm)and four ice-content levels(0%,20%,40%,60%).Run-out distance,velocity,energy components,flow regime(Savage number),and segregation indexαwere quantified.Increasing ice content significantly enhances mobility,but with diminishing marginal effectiveness.From 0%to 40%ice content,run-out distance increases by 41%-86%,whereas the additional increase from 40%to 60%contributes only 12%-23%.Particle-size ratio strongly governs segregation intensity.Fine-gravel groups reach segregation indices ofα=0.92-0.98,indicating nearly complete upward migration of ice,whereas medium-gravel and coarse-gravel groups exhibit much weaker segregation,stabilizing atα=0.68-0.74 and 0.60-0.69.Savage number analyses reveal marked flow-regime transitions.At 0%ice content,Savage numbers reach 1.0-1.5,indicating a collisional regime.Increasing ice content suppresses collisionality,with Savage numbers decreasing to 0.03-0.07 at 60%ice content,consistent with dense-regime flow.DEM energy analyses confirm this regime shift:for finegravel mixtures,collision energy decreases by 14%,while sliding-friction energy increases by 33%as ice content increases from 0%to 60%,reflecting enhanced overburden effects imposed by upward-segregated ice layers.Medium and coarse mixtures exhibit weaker or opposite energy-shift patterns,demonstrating strong size dependence.Mechanistically,large particle-size contrasts promote strong segregation and form dense basal rock layers that increase basal friction and reduce mobility.When particle sizes are similar or ice content is high,segregation remains limited,allowing ice to mix into the basal layer,thereby reducing basal friction and enhancing mobility.This research quantitatively demonstrates how composition controls particle spatial distribution,flow regime,and energy dissipation,offering new mechanistic insights into the propagation and deposition behaviors of rock-ice avalanches and improving hazard assessment in vulnerable high-mountain regions.
基金supported in part by the Anhui Provincial Natural Science Foundation Youth Project(Category C)under Grant No.2508085QE184the Opening Project of Key Laboratory of Power Electronics and Motion Control of Anhui Higher Education Institutions under Grant No.PEMC24004+1 种基金the Anhui University of Technology Young Teachers Research Fund under Grant No.QZ202412the Scientific Research Startup Fund for Introduced Talents of Anhui University of Technology under Grant No.QD202340.
文摘In this paper,a comprehensive evaluation on the silicon/silicon carbide(Si/SiC)hybrid switch is performed through experimental tests in terms of both electrical performance and robustness under extreme stresses.Based on the optional turn-on and turn-off delay times under the efficiency control mode obtained from the double-pulse test(DPT),both nondestructive and destructive single-pulse avalanche tests are conducted on the Si/SiC hybrid switch as well as on the two discrete device branches inside the hybrid switch.In addition,the avalanche voltage,critical avalanche energy,and peak avalanche current,which intrinsically characterize the unclamped-inductive-switching(UIS)avalanche characteristics,are carefully examined.In this way,the physical factors dominating the UIS characteristics of the hybrid switch,thus limiting its single-pulse avalanche withstand capability,are specifically and comprehensively identified;the underlying physical mechanisms are analyzed and revealed in depth,and how the gate control sequence affects the UIS characteristics of the hybrid switch is extensively investigated.We additionally carry out short-circuit(SC)tests under the fault-under-load(FUL)condition and perform a parallel in-depth analysis to experimentally determine which branch dominates the SC withstand capability of the hybrid switch.Our experimental study indicates that,for both SC robustness and single-pulse avalanche capability,the limiting factor is a single device branch among the two parallel discrete devices,and the UIS behavior is sensitive to the variation of the gate turn-off delay time Toff_delay.The study conducted in this paper not only provides deep academic insights into the electrical performance and reliability of the Si/SiC hybrid switch,but also offers fundamental theoretical principles and technical evidence to support its more efficient and long-term reliable applications of the hybrid switch in the industrial fields.
基金supported by the National Natural Science Foundation of China(Nos.U2167202,12225504,12005276)the Natural Science Foundation of Shandong Province(No.ZR2024QA172)the Fundamental Research Funds of Shandong University.
文摘A 32-channel charge-sensitive amplifier(CSA)is designed for fast timing in the delay-line readout of a parallel plate avalanche counter(PPAC)array.It is realized on a PCB with operational amplifiers and other discrete components.Each channel consists of an integrator,a pole-zero cancellation net,and a linear amplification stage,which can be adapted to accommodate either positive or negative input signals.The RMS equivalent input noise charges are 3.3 fC,the conversion gains are approximately±2 mV∕fC,and the intrinsic time resolution reaches 32 ps.In the prototype PPAC application,the CSA performs as well as the commercial FTA820A amplifier,providing a position resolution as good as 0.17 mm,and exhibiting reliable stability during several hours of continuous data acquisition.
基金supported in part by the National Natural Science Foundation of China under Grant 62071073in part by the Fundamental Research Funds for Central Universities under Grant 2023CDJXY-041in part by the Foundation from Guangxi Key Laboratory of Optoelectronic Information Processing under Grant GD20201.
文摘The dynamic avalanche effect is a critical factor influencing the performance and reliability of the field-stop insulated gate bipolar transistors(FS-IGBT).Unclamped inductive switching(UIS)is the primary method for testing the dynamic avalanche capability of FS-IGBTs.Numerous studies have demonstrated that factors such as device structure,avalanche-generating current filaments,and electrical parameters influence the dynamic avalanche effect of the FS-IGBT.However,few studies have focused on enhancing the avalanche reliability of the FS-IGBT by adjusting circuit parameters during operation.In this paper,the dynamic avalanche effect of the FS-IGBT under UIS conditions is comprehensively investigated through a series of comparative experiments with varying circuit parameters,including bus voltage V_(DC),gate voltage V_(G),gate resistance R_(g),load inductance L,and temperature TC.Furthermore,a method to enhance the dynamic avalanche reliability of the FS-IGBT under UIS by optimizing circuit parameters is proposed.In practical applications,reducing gate voltage,increasing load inductance,and lowering temperature can effectively improve the dynamic avalanche capability of the FS-IGBT.
文摘This study represents a pioneering effort to analyze the impact of avalanches descending into Morskie Oko from Marchwiczny Gully,the most active avalanche path around the lake.It focuses on catastrophic avalanches that descended from the analyzed gully,as reported in the literature from the 1900s until now.However,only the data collected in recent years,our field studies,combined with modern LIDAR data and GIS-based modeling,allowed us to perform a detailed analysis.The GIS-based approach effectively uses spatial data to address snow avalanche modeling challenges.Although the study area lies within Tatra National Park,no official services carry out systematic avalanche monitoring or measurements.The impact of hazardous events,such as snow avalanches,on the most famous Polish mountain lake,Morskie Oko,has been poorly described in the literature and has yet to be discovered.Therefore,to analyze the selected avalanche parameters,we mainly used our ground and additional aerial photographs taken by local mountain services and related field measurements.Our analysis resulted in figurative estimates of the extent and volume of avalanche snow and its weight,both on the surface of the ice sheet and the part of the avalanche that did not reach the lake's shore and remained on the slope of Marchwiczny Gully.For example,the values for the mighty avalanche on February 3,2023,are 23,500 m~3 and 4,700 tons on the ice surface and 20,000 m~3 and 4,000 tons on the slope.It was determined that avalanches that descend onto the studied lake's surface result in its shallowing.This process occurs because of sedimentation of slope material carried by avalanches,especially during the final phase of ice cover melting.When openings appear in the solid ice cover in spring,floating ice can migrate,driven by wind pressure,and deposit avalanche material in various parts of the lake bottom.Thus,avalanches contributed to the gradual disappearance of the lake.
基金supported by National Natural Science Foundation of China(NO.42371085)the Tibet Science and Technology Program(XZ202201ZY0011G)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0906).
文摘Snow avalanches present a significant threat to infrastructure,affecting buildings,roads,railways,and power lines,and frequently leading to massive economic losses in livelihoods and production.With the increase in regional temperatures and the occurrence of extreme snowfall events,the frequency and intensity of avalanches have escalated,resulting in more severe incidents and higher casualty rates.As natural archives of environmental changes,tree rings offer valuable proxies for avalanche hazard assessments in regions where direct observation data is scarce,particularly in high-altitude regions.The dendrogeomorphology has been gradually being applied in avalanche hazard evaluation,however,it remains limited in China.To address this gap,this study systematically investigates the principles and methodologies for reconstructing avalanche histories and evaluates their applications in avalanche hazard assessments through a literature review and field observations.It provides a comprehensive overview of recent advancements in key areas,including the impact of avalanches on forest ecosystems,the reconstruction of avalanches,and the analysis of avalanche events(i.e.,the spatiotemporal distribution,the historical recurrence intervals,magnitudes,and triggering conditions of avalanches).Considering the current limitations in avalanche hazard assessments and the urgent need for such research in China,we outline key priorities and future directions,including refining reconstruction methodologies,developing a comprehensive tree-ring-based avalanche database for high-altitude regions,and establishing an advanced hazard assessment framework based on dendrochronological evidence.
基金supported by the National Natural Science Foundation of China(Grant Nos.42307194 and 42120104002)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2024QNRC001).
文摘The impact of cross-sectional topographic variability on the kinetic properties of granular flows has been underexplored,which hinders the understanding of the kinematics of rock avalanches.In this study,the throat contraction index(T)is introduced to quantify variations in throat topography,and 96 numerical simulation experiments with varying T and slope angles(δ)are conducted.The findings indicate that granular flows experience transient obstructions when traversing throat topographies,primarily due to the periodic formation and breaking of the arch structure.Observations suggest that the acceleration of velocity in the tails of granular flows is restrained by the throat region,potentially altering the dynamics of related geohazards.In this study,the impact of throat topography is quantitatively assessed,demonstrating a reduction in peak flowrates of granular materials by 20%-80% and extending the flowduration up to six times.The present study proposes the throat-induced hazard index(Φ)to evaluate the influenceof throat topography on the risk of rockslides and avalanches characterized by granular flows,which may provide insights for the design of mitigation structures in topographic regions.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2244227,42277126 and 41977215).
文摘Air blasts induced by rock-ice avalanches are common natural phenomena known for their far-field destructive impact.In this study,remote sensing images,eyewitness videos and numerical modelling were comprehensively applied to analyze the initiation and propagation of the 2021 Chamoli avalancheinduced air blast.Our findings indicate that air blasts are observed from the avalanche source area to the Rishiganga valley,but nearly disappear in the Dhauliganga valley.The most intense air blast is concentrated on the left side of Ronti Gad valley,with maximum velocity and pressure estimated at over 70 m/s and 20 kPa,respectively.Such high pressure results in widespread tree breakage in the area.Based on the analysis of the Chamoli event,we further discussed the potential contribution of the avalanche flow regime,avalanche dynamics and geomorphology to the destructive potential of air blasts.Rapidly moved sliding mass can impart the air blast a high initial momentum,and this process will be exaggerated when the avalanche impacts valley walls at bends.However,when the rock-ice avalanche transforms into a debris-enriched flash flood,free water within the flowing mass can displace air,inhibiting the generation of air blasts.Our work offers new insights into the generation and propagation of rock-ice avalanche-induced air blasts,underscoring the importance of including this type of hazard during avalanche risk assessment in high-altitude glacial regions.
基金financially supported by the National Natural Science Foundation of China(Nos.42207197,42293355,41672285,42293350,42341101)the Fundamental Research Funds for the Central Universities(Nos.300102264917,300102262908,590123008)。
文摘Massive granitic rock avalanches are extensively developed in the middle section of the northern Qinling Mountains(NQM),China.The current consensus is that their formation could have been connected with seismic events that occurred in the NQM.However,there is a lack of systematic discussion on the genetic dynamics of these rock avalanches.Hence,taking Earth system scientific research as a starting point,this paper systematically summarizes and discusses development characteristics,formation times and genetic dynamic mechanisms of granitic rock avalanches in the NQM based on geological investigations,high-precision remote sensing interpretations,geomorphological dating,geophysical exploration,and a large-scale shaking table model test.We identified 53 granitic rock avalanches in this area,with a single collapse area ranging from 0.01×10~6 to 1.71×10~6 m^(2).Their development time can be divided into six stages,namely,107000 years BP,11870–11950 years BP,11000 years BP,2300 years BP,1800 years BP,and 1500 years BP,which were closely related to multiple prehistoric or ancient earthquakes.We suggest that long-term coupling of internal and external earth dynamics was responsible for the granitic rock avalanches in the NQM;the internal dynamics were mainly related to subduction,collision and extrusion of different plates under the Qinling terrane,leading to the formation and tectonic uplift of the Qinling orogenic belt;and the external dynamics were closely associated with climate changes resulting in mountain denudation,freeze-thaw cycles and isostatic balance uplift.In this process,the formation and evolution of the Qinling orogenic belt play a geohazard-pregnant role,structural planes,including faults and joints,play a geohazard-controlled role,and earthquakes play a geohazard-induced role,which jointly results in the occurrence of large-scale granitic rock avalanches in the NQM.This research can not only decipher the genetic dynamic mechanism of large hard granitic rock avalanches but also reveal temporal and spatial patterns of the evolution of breeding and the generation of large-scale rock avalanches in the margins of orogenic belts.
基金funded by the Key Science and Technology Project of Transportation Industry(2022-ZD6-090)Xinjiang Transportation Science and Technology Project(2022-ZD-006)+1 种基金Xinjiang Transportation Investment 2021"Unveiling the List of Commander-in-Chief"Science and Technology Project(ZKXFWCG2022060004)the Science and Technology Research and Development Project(KY2022021501)of Xinjiang Transportation Design Institute。
文摘In this study,avalanches in the Aerxiangou section of the Duku Expressway in the Tianshan Mountain area of Xinjiang were taken as the research object,and 92 avalanches were accurately identified through onsite research.A high-resolution three-dimensional model was established by collecting images from unmanned aerial vehicles for an in-depth understanding of the avalanche danger of the region,according to the sample set selection of different uses of machine learning support vector machines to establish the S1-RBFKSVM,S1-PKSVM,S2-RBFKSVM,and S2-PKSVM avalanche susceptibility coupling models.On the basis of the avalanche point susceptibility,the impact velocity,impact force,avalanche volume,and throw distance constitute the hazard evaluation system.The study results revealed that slopes in the range of 26.6°–46.9°are more prone to avalanches,and sample set 2 improved the accuracy by approximately 30%compared with sample set 1 trained in the avalanche susceptibility model.Principal component analysis revealed a total of 16 high-risk avalanches,which were distributed mainly on the southern side of the route.This study provides data support for avalanche simulations as well as early warning and prevention and provides theoretical and methodological guidance for the construction and operation of the Duku Expressway.
基金supported by Chinese Academy of Sciences(CAS)program of"Western Youth Scholar"(E2R2050050)。
文摘Large-scale ice avalanches pose serious risks owing to their high speed and long travel distances,and their mobility is increased by ice melting owing to frictional heat.Most motion models for largescale ice avalanches have been constructed for specific scenarios,neglecting the key effect of frictional ice melting on their mobility and having limited applicability.In this study,a two-dimensional model combining thermodynamic and dynamic properties was proposed.This model,based on depth-averaged and granular flow theories,considers the friction weakening process to simulate the dynamics of ice avalanches.The governing equations for motion and heat transfer were solved by employing the finite volume and the Crank-Nicolson methods.The numerical simulation results showed that the friction weakening caused by the thermal effect on the sliding surface significantly reduced the friction coefficient between the ice mass and its substrate,increasing the travel distance of ice avalanches.The initial ice content in the shear band affects the friction coefficient during the viscous and Coulomb friction stages.The higher the initial ice content in the shear band,the lower the viscous resistance during the frictional heatinginduced drag reduction stage,resulting in a longer sliding distance and larger coverage area.Notably,large-scale ice avalanches exhibit a"Volume Effect"similar to other mass movements such as landslides,debris flows,and rock avalanches.Ice avalanches with larger volumes exhibit greater mobility and coverage areas.The proposed model reveals the dynamic characteristics of large-scale ice avalanches under the effect of frictional heat and offers a valuable tool for dynamic analysis and supporting disaster risk reduction strategies.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2240221 and 52379105)the National Key R&D Program of China(Grant No.2022YFC3080100).
文摘Debris avalanches are a major concern due to their high mobility.However,the mechanism of friction weakening in debris avalanches remains poorly understood.This study systematically investigates the friction weakening mechanism of granular flows using rotation drum experiments,large-scale chute experiments,and numerical simulations.Notably,dilation of granular flows is a characteristic feature associated with friction weakening.The results indicate that dilation occurs synchronously with friction weakening during the motion of granular flows,as evidenced by the motion patterns and force interactions of debris avalanches.Collision contacts were identified as the primary driver of particle dilation.An optimal collision strength can induce dilation of granular flows,reducing contact between the sliding body and substrate,thereby leading to friction weakening.The peak collision strength of granular flows during movement is determined by fragment size.The critical condition for triggering friction weakening in debris avalanches is identified as the peak Savage number(Ns,p)greater than 1.06.A mathematical model based on the granular inertial collision-friction coupling equation was developed.This study provides compelling evidence that the fractal dimension of various types of high-speed debris avalanches tends to stabilize within a narrow range.
文摘A near-infrared single-photon detection system is established by using pigtailed InGaAs/InP avalanche photodiodes. With a 50GHz digital sampling oscilloscope, the function and process of gated-mode （Geiger-mode） single-photon detection are intuitionally demonstrated for the first time. The performance of the detector as a gated-mode single-photon counter at wavelengths of 1310 and 1550nm is investigated. At the operation temperature of 203K,a quantum efficiency of 52% with a dark count probability per gate of 2.4 × 10 ^-3 ,and a gate pulse repetition rate of 50kHz are obtained at 1550nm. The corresponding parameters are 43%, 8.5 × 10^-3 , and 200kHz at 238K.
