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
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
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
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
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
Rock-ice avalanches have frequently occurred in the Eastern Himalayan Syntaxis region due to climate change and active tectonic movements.These events commonly trigger catastrophic geohazard chains,including debris fl...Rock-ice avalanches have frequently occurred in the Eastern Himalayan Syntaxis region due to climate change and active tectonic movements.These events commonly trigger catastrophic geohazard chains,including debris flows,river blockages,and floods.This study focuses on the Zelongnong Basin,analyzing the geomorphic and dynamic characteristics of high-altitude disasters.The basin exhibits typical vertical zonation,with disaster sources initiating at elevations exceeding 4000 m and runout distances reaching up to 10 km.The disaster chain movement involves complex dynamic effects,including impact disintegration,soil-rock mixture arching,dynamic erosion,and debris deposition,enhancing understanding of the flow behavior and dynamic characteristics of rock-ice avalanches.The presence of ice significantly increases mobility due to lubrication and frictional melting.In the disaster event of September 10,2020,the maximum flow velocity and thickness reached 40 m/s and 43 m,respectively.Furthermore,continuous deformation of the Zelongnong glacier moraine was observed,with maximum cumulative deformations of 44.68 m in the distance direction and 25.96 m in the azimuth direction from March 25,2022,to August 25,2022.In the future,the risk of rock-ice avalanches in the Eastern Himalayan Syntaxis region will remain extremely high,necessitating a focus on early warning and risk mitigation strategies for such basin disasters.展开更多
As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge ...As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge on IAs remains lacking.We summarized 63 IAs on the Tibetan Plateau(TP)since the 20th century,of which,over 20 IAs occurred after the 21st century.The distributions of IAs are mainly concentrated in the southeastern and northwestern TP,and the occurrence time of IAs is mostly concentrated from July to September.We highlight recent advances in mechanical properties and genetic mechanisms of IAs and emphasize that temperature,rainfall,and seismicity are the inducing factors.The failure modes of IAs are summarized into 6 categories by examples:slip pulling type,slip toppling type,slip breaking type,water level collapse type,cave roof collapse type,and wedge failure type.Finally,we deliver recommendations concerning the risk assessment and prediction of IAs.The results provide important scientific value for addressing climate change and resisting glacier-related hazards.展开更多
Rock avalanches are generally difficult to prevent and control due to their high velocities and the extensive destruction they cause.However,barrier structures constructed along the path of a rock avalanche can partia...Rock avalanches are generally difficult to prevent and control due to their high velocities and the extensive destruction they cause.However,barrier structures constructed along the path of a rock avalanche can partially mitigate the magnitudes and consequences of such catastrophic events.We selected a rock avalanche in Nayong County,Guizhou Province,China as a case to study the effect of the location and height of a retaining wall on the dynamic characteristics of rock avalanche by using both actual terrain-based laboratory-model tests and coupled PFC3D-FLAC3D numerical simulations.Our findings demonstrate that a retaining wall can largely block a rock avalanche and its protective efficacy is significantly influenced by the integrity of the retaining wall.Coupled numerical simulation can serve as a powerful tool for analyzing the interaction between a rock avalanche and a retaining wall,facilitating precise observations of its deformation and destruction.The impact-curve characteristics of the retaining wall depend upon whether or not the rock avalanche-induced destruction is taken into account.The location of the retaining wall exerts a greater influence on the outcome compared to the height and materials of the retaining wall,while implementing a stepped retaining-wall pattern in accordance with the terrain demonstrates optimal efficacy in controlling rock avalanche.展开更多
Large-scale rock-ice avalanches resulting from the interaction of tectonics and climate are characterized with high mobility,huge volumes of sediment,and rapid denudation,being a major agent of landscape evolution in ...Large-scale rock-ice avalanches resulting from the interaction of tectonics and climate are characterized with high mobility,huge volumes of sediment,and rapid denudation,being a major agent of landscape evolution in high altitude mountainous regions.Specifically,the extreme glaciated slope failures often transform into extraordinarily large and mobile debris flows,resulting in disastrous consequences such as sedimentation and desertification.Due to a dearth of on-site observation data and experimental data collection,our comprehension of the geomorphic and kinematic characteristics of rock-ice avalanches remains poor.Here we report a cluster of ancient rock-ice avalanches spreading along the Chomolhari range of the China-Bhutan Himalayas.By integrating remote sensing image interpretation with detailed field investigations,we demonstrate the geomorphic and sedimentary characteristics of four events among the avalanches.The estimated volumes of the four are 23.73 Mm³,39.69 Mm³,38.43 Mm³,and 38.25 Mm³,respectively.The presence of pre-existing moraines or alluvial fans constrained their movement,resulting in deposition features such as marginal digitated lobes at higher elevations and large depressed areas in the interior.Applying the Savage-Hutter theory,we calculate the basal friction angle and travel angle of these ancient rock-ice avalanches that are both less than 10°,affirming the similarity of these avalanches in the study area to those occurring in other regions.Our study significantly contributes to understanding the geomorphic and kinematic characteristics of rock-ice avalanches in high-altitude mountainous regions,providing valuable insights into their response to the disproportionate growth of Himalayan peaks.展开更多
Numerical simulation is employed to investigate the initial state of avalanche in polydisperse particle systems.Nucleation and propagation processes are illustrated for pentadisperse and triadisperse particle systems,...Numerical simulation is employed to investigate the initial state of avalanche in polydisperse particle systems.Nucleation and propagation processes are illustrated for pentadisperse and triadisperse particle systems,respectively.In these processes,particles involved in the avalanche grow slowly in the early stage and explosively in the later stage,which is clearly different from the continuous and steady growth trend in the monodisperse system.By examining the avalanche propagation,the number growth of particles involved in the avalanche and the slope of the number growth,the initial state can be divided into three stages:T1(nucleation stage),T2(propagation stage),T3(overall avalanche stage).We focus on the characteristics of the avalanche in the T2 stage,and find that propagation distances increase almost linearly in both axial and radial directions in polydisperse systems.We also consider the distribution characteristics of the average coordination number and average velocity for the moving particles.The results support that the polydisperse particle systems are more stable in the T2 stage.展开更多
In mountainous areas,snow avalanches could be triggered by the shaking produced by earthquakes.The forces induced by the earthquake can cause an irregular increase of shear strength load down the slope,for the presenc...In mountainous areas,snow avalanches could be triggered by the shaking produced by earthquakes.The forces induced by the earthquake can cause an irregular increase of shear strength load down the slope,for the presence of complex surface and buried morphologies.Topographic irregularities generate maximum effects of waves amplification linked to wavelengths comparable to the horizontal dimension of the topographic feature.For this reason,the selected time-histories represent an appropriate input for the two-dimensional numerical response analyses when a dynamic phenomenon produce the resonant motion of a whole mountain.This represents an important earthquake-induced hazard in snow-covered mountain areas with high probability of seismic events.Some valleys are located in regions with scare ground motion data and investments on infrastructures are not always accompanied by adequate protection against earthquake-induced avalanches.The paper points out a simple deterministic approach for selecting a set of real accelerograms applied to a real case of Siella Mountain(Central Italy)where a large avalanche destroying a tourist facility of Rigopiano resort on 18 January 2017.The selected time histories were used as input for the two-dimensional numerical model of the subsoil to evaluate the topographic seismic amplification in ridge and compare it with the results of other authors.These methods suggest that morphology-related inertial effects should be considered as an overload action on snow layers when controlling multi-hazard studies and spatial planning.展开更多
The development of InGaAs/InP single-photon avalanche photodiodes(SPADs)necessitates the utiliza-tion of a two-element diffusion technique to achieve accurate manipulation of the multiplication width and the dis-tribu...The development of InGaAs/InP single-photon avalanche photodiodes(SPADs)necessitates the utiliza-tion of a two-element diffusion technique to achieve accurate manipulation of the multiplication width and the dis-tribution of its electric field.Regarding the issue of accurately predicting the depth of diffusion in InGaAs/InP SPAD,simulation analysis and device development were carried out,focusing on the dual diffusion behavior of zinc atoms.A formula of X_(j)=k√t-t_(0)+c to quantitatively predict the diffusion depth is obtained by fitting the simulated twice-diffusion depths based on a two-dimensional(2D)model.The 2D impurity morphologies and the one-dimensional impurity profiles for the dual-diffused region are characterized by using scanning electron micros-copy and secondary ion mass spectrometry as a function of the diffusion depth,respectively.InGaAs/InP SPAD devices with different dual-diffusion conditions are also fabricated,which show breakdown behaviors well consis-tent with the simulated results under the same junction geometries.The dark count rate(DCR)of the device de-creased as the multiplication width increased,as indicated by the results.DCRs of 2×10^(6),1×10^(5),4×10^(4),and 2×10^(4) were achieved at temperatures of 300 K,273 K,263 K,and 253 K,respectively,with a bias voltage of 3 V,when the multiplication width was 1.5µm.These results demonstrate an effective prediction route for accu-rately controlling the dual-diffused zinc junction geometry in InP-based planar device processing.展开更多
Stagnant lid planets are characterized by a globe-encircling,conducting lid that is thick and strong,which leads to reduced global surface heat flows.Consequently,the mantles of such planets can have warmer interiors ...Stagnant lid planets are characterized by a globe-encircling,conducting lid that is thick and strong,which leads to reduced global surface heat flows.Consequently,the mantles of such planets can have warmer interiors than Earth,and interestingly,a pyrolitic mantle composition under warmer conditions is predicted to have a distinctly different mantle transition zone compared to the present-day Earth(Hirose,2002;Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014;Dannberg et al,2022).Instead of olivine primarily transforming into its higher-pressure polymorphs such as wadsleyite and then ringwoodite,at pressures corresponding to 410 km and 520 km depth in Earth,respectively,it instead transforms into a mineral assemblage of wadsleyite,majorite,and ferropericlase(WMF),and then to majorite+ferropericlase(MF),before finally transforming into bridgmanite at pressures corresponding to 660 km depth in Earth(Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014).Convective motions in stagnant lid planets are dominated by small-scale instabilities(cold drips)forming within the mobile rheological sublayer under the rigid lid.Using ASPECT and a thermodynamic model of a pyrolitic mantle composition generated by HeFESTo,we show that under certain conditions,the small drips can pond atop the WMF-MF mineral phase transition.The barrier to convective flow arises from the WMF mineral phase assemblage having an effective negative thermal expansivity(Stixrude and Lithgow-Bertelloni,2022).Although large-scale downwellings that typically occur within mobile lid planets are able to pass through the WMF zone without difficulty(Dannberg et al.,2022;Li RP et al.,2024),the smaller and less negatively buoyant nature of downwelling drips in stagnant lid planets are more susceptible to these effects,which leads to an ephemeral layering of the mantle.Our numerical models show that in stagnant lid planets with mantle potential temperatures that exceed 1900 K,the smaller,cold drips from the lid continue to pile up until enough of them have coalesced that they collectively avalanche as a larger instability into the deeper interior.展开更多
Snow avalanches are a common natural hazard in many countries with seasonally snow-covered mountains.The avalanche hazard varies with snow avalanche type in different snow climate regions and at different times.The ab...Snow avalanches are a common natural hazard in many countries with seasonally snow-covered mountains.The avalanche hazard varies with snow avalanche type in different snow climate regions and at different times.The ability to understand the characteristics of avalanche activity and hazards of different snow avalanche types is a prerequisite for improving avalanche disaster management in the mid-altitude region of the Central Tianshan Mountains.In this study,we collected data related to avalanche,snowpack,and meteorology during four snow seasons(from 2015 to 2019),and analysed the characteristics and hazards of different types of avalanches.The snow climate of the mid-altitude region of the Central Tianshan Mountains was examined using a snow climate classification scheme,and the results showed that the mountain range has a continental snow climate.To quantify the hazards of different types of avalanches and describe their situation over time in the continental snow climate region,this study used the avalanche hazard degree to assess the hazards of four types of avalanches,i.e.,full-depth dry snow avalanches,full-depth wet snow avalanches,surface-layer dry snow avalanches,and surface-layer wet snow avalanches.The results indicated that surface-layer dry snow avalanches were characterized by large sizes and high release frequencies,which made them having the highest avalanche hazard degree in the Central Tianshan Mountains with a continental snow climate.The overall avalanche hazard showed a single peak pattern over time during the snow season,and the greatest hazard occurred in the second half of February when the snowpack was deep and the temperature increased.This study can help the disaster and emergency management departments rationally arrange avalanche relief resources and develop avalanche prevention strategies.展开更多
The avalanche warning service was established within the operational European territorial cooperation program Slovenia-Austria （SI-AT） 2007-2013 project ＂Natural Hazards without Frontiers＂. Four institutes, two fr...The avalanche warning service was established within the operational European territorial cooperation program Slovenia-Austria （SI-AT） 2007-2013 project ＂Natural Hazards without Frontiers＂. Four institutes, two from Austria and two from Slovenia, work together to publish an avalanche report during the winter season. The first regular season was the winter 2012/2013. The avalanche and the slab avalanche situation in the transnational area along the 160 km border between the south of Austria and north of Slovenia show major differences of avalanche building weather situations. Because of the nearby sea in the southwest of Slovenia, the prevailing weather situations for high precipitation are coming from southwest or southeast. Nevertheless sometimes a lot of fresh snow occurs at northerly weather situations, which is unusual for Slovenian Alps and is therefore poorly forecasted for this region. Austrian avalanche experts are facing the same problems at southerly weather situations. Hence, an exchange of experience, weather data as well as model information improves the avalanche warning on both sides of the Austrian-Slovenian border.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
Analyzing large prehistoric rock avalanches provides significant data for evaluating the disaster posed by these relatively infrequent but destructive geological events. This paper attempts to study the characteristic...Analyzing large prehistoric rock avalanches provides significant data for evaluating the disaster posed by these relatively infrequent but destructive geological events. This paper attempts to study the characteristics and dynamics of the Ganqiuchi granitic rock avalanche, in the middle of the northern margin of Qinling Mountains, 30 km to the south of Xi’an, Shaanxi Province, China. In plane view, this rock avalanche is characterized by source area, accumulation area and dammed lake area. Based on previous studies, historical records and regional geological data, the major trigger of the Ganqiuchi rock avalanche is considered to be a strong paleo-earthquake with tremendous energy. The in situ deposit block size distributions of the intact rock mass and the debris deposits are presented and analyzed by using a simple model for estimating the number of fragmentation cycles that the blocks underwent. The results show that the primary controlling factor of the fragmentation process is the pre-existing fractures, and there is a relationship between the potential energy and the fragmentation energy: the latter is approximately 20% of the former. Based on the dynamic discrete element technique, the study proposes a four-stage model for the dynamic course of the Ganqiuchi rock avalanche:(1) failing;(2) highspeed sliding;(3) collision with obstacles;(4) decelerated sliding, which has implication for hazard assessment of the potential rock avalanches in China and other countries with similar geological setting.展开更多
A set of detected avalanches from January to April 2012 on a hillside southeast of lschgl, Austria is given. The avalanches are off-the-cut or caused by blast. The meteorological data of two monitoring stations nearby...A set of detected avalanches from January to April 2012 on a hillside southeast of lschgl, Austria is given. The avalanches are off-the-cut or caused by blast. The meteorological data of two monitoring stations nearby the hillside are taken for analysing the weather situation. The meteorological parameters air temperature, wind intensity and wind speed, relative humidity, precipitation and snow depth are investigated for similarities short before and during an avalanche. The avalanches are grouped into three categories and meteorological characteristics are found for each category. Thereby the avalanche hazard for the observed hillside is better assessed and an infrastructure safety by avalanche control due to concerted avalanche blasts is more effective. The result of the analysis shows three kinds of hazard weather conditions, which increase the avalanche hazard： warm air temperatures cause a settlement of the snow pack, but in the beginning of the process a weakening in the snow pack happens. Rapidly decreasing of the air temperature cause cracks in the snow pack and the combination of fresh snow and strong wind speed leads to accumulation of snow on sheltered slopes.展开更多
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 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.
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granted by the National Natural Science Foundation of China(Grant Nos.U2244227 and U2244226)the National Key R&D Program of China(Grant No.2022YFC3004301)China Geological Survey Project(Grant No.DD20230538)。
文摘Rock-ice avalanches have frequently occurred in the Eastern Himalayan Syntaxis region due to climate change and active tectonic movements.These events commonly trigger catastrophic geohazard chains,including debris flows,river blockages,and floods.This study focuses on the Zelongnong Basin,analyzing the geomorphic and dynamic characteristics of high-altitude disasters.The basin exhibits typical vertical zonation,with disaster sources initiating at elevations exceeding 4000 m and runout distances reaching up to 10 km.The disaster chain movement involves complex dynamic effects,including impact disintegration,soil-rock mixture arching,dynamic erosion,and debris deposition,enhancing understanding of the flow behavior and dynamic characteristics of rock-ice avalanches.The presence of ice significantly increases mobility due to lubrication and frictional melting.In the disaster event of September 10,2020,the maximum flow velocity and thickness reached 40 m/s and 43 m,respectively.Furthermore,continuous deformation of the Zelongnong glacier moraine was observed,with maximum cumulative deformations of 44.68 m in the distance direction and 25.96 m in the azimuth direction from March 25,2022,to August 25,2022.In the future,the risk of rock-ice avalanches in the Eastern Himalayan Syntaxis region will remain extremely high,necessitating a focus on early warning and risk mitigation strategies for such basin disasters.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0201)the National Natural Science Foundation of China(Grant No.42377199,No.41941019)+1 种基金State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2021Z005)Chengdu University of Technology Postgraduate Innovative Cultivation Program(Grant No.CDUT2023BJCX008).
文摘As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge on IAs remains lacking.We summarized 63 IAs on the Tibetan Plateau(TP)since the 20th century,of which,over 20 IAs occurred after the 21st century.The distributions of IAs are mainly concentrated in the southeastern and northwestern TP,and the occurrence time of IAs is mostly concentrated from July to September.We highlight recent advances in mechanical properties and genetic mechanisms of IAs and emphasize that temperature,rainfall,and seismicity are the inducing factors.The failure modes of IAs are summarized into 6 categories by examples:slip pulling type,slip toppling type,slip breaking type,water level collapse type,cave roof collapse type,and wedge failure type.Finally,we deliver recommendations concerning the risk assessment and prediction of IAs.The results provide important scientific value for addressing climate change and resisting glacier-related hazards.
基金Hunan Provincial key Laboratory of key Technology on Hydropower Development Open Research Fund (PKLHD202203)
文摘Rock avalanches are generally difficult to prevent and control due to their high velocities and the extensive destruction they cause.However,barrier structures constructed along the path of a rock avalanche can partially mitigate the magnitudes and consequences of such catastrophic events.We selected a rock avalanche in Nayong County,Guizhou Province,China as a case to study the effect of the location and height of a retaining wall on the dynamic characteristics of rock avalanche by using both actual terrain-based laboratory-model tests and coupled PFC3D-FLAC3D numerical simulations.Our findings demonstrate that a retaining wall can largely block a rock avalanche and its protective efficacy is significantly influenced by the integrity of the retaining wall.Coupled numerical simulation can serve as a powerful tool for analyzing the interaction between a rock avalanche and a retaining wall,facilitating precise observations of its deformation and destruction.The impact-curve characteristics of the retaining wall depend upon whether or not the rock avalanche-induced destruction is taken into account.The location of the retaining wall exerts a greater influence on the outcome compared to the height and materials of the retaining wall,while implementing a stepped retaining-wall pattern in accordance with the terrain demonstrates optimal efficacy in controlling rock avalanche.
基金funded by the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0902)the National Natural Science Foundation of China(91747207,41790434)。
文摘Large-scale rock-ice avalanches resulting from the interaction of tectonics and climate are characterized with high mobility,huge volumes of sediment,and rapid denudation,being a major agent of landscape evolution in high altitude mountainous regions.Specifically,the extreme glaciated slope failures often transform into extraordinarily large and mobile debris flows,resulting in disastrous consequences such as sedimentation and desertification.Due to a dearth of on-site observation data and experimental data collection,our comprehension of the geomorphic and kinematic characteristics of rock-ice avalanches remains poor.Here we report a cluster of ancient rock-ice avalanches spreading along the Chomolhari range of the China-Bhutan Himalayas.By integrating remote sensing image interpretation with detailed field investigations,we demonstrate the geomorphic and sedimentary characteristics of four events among the avalanches.The estimated volumes of the four are 23.73 Mm³,39.69 Mm³,38.43 Mm³,and 38.25 Mm³,respectively.The presence of pre-existing moraines or alluvial fans constrained their movement,resulting in deposition features such as marginal digitated lobes at higher elevations and large depressed areas in the interior.Applying the Savage-Hutter theory,we calculate the basal friction angle and travel angle of these ancient rock-ice avalanches that are both less than 10°,affirming the similarity of these avalanches in the study area to those occurring in other regions.Our study significantly contributes to understanding the geomorphic and kinematic characteristics of rock-ice avalanches in high-altitude mountainous regions,providing valuable insights into their response to the disproportionate growth of Himalayan peaks.
基金Project supported by the Qingdao National Laboratory for Marine Science and Technology(Grant No.2015ASKJ01)the National Natural Science Foundation of China(Grant Nos.11972212,12072200,and 12002213).
文摘Numerical simulation is employed to investigate the initial state of avalanche in polydisperse particle systems.Nucleation and propagation processes are illustrated for pentadisperse and triadisperse particle systems,respectively.In these processes,particles involved in the avalanche grow slowly in the early stage and explosively in the later stage,which is clearly different from the continuous and steady growth trend in the monodisperse system.By examining the avalanche propagation,the number growth of particles involved in the avalanche and the slope of the number growth,the initial state can be divided into three stages:T1(nucleation stage),T2(propagation stage),T3(overall avalanche stage).We focus on the characteristics of the avalanche in the T2 stage,and find that propagation distances increase almost linearly in both axial and radial directions in polydisperse systems.We also consider the distribution characteristics of the average coordination number and average velocity for the moving particles.The results support that the polydisperse particle systems are more stable in the T2 stage.
文摘In mountainous areas,snow avalanches could be triggered by the shaking produced by earthquakes.The forces induced by the earthquake can cause an irregular increase of shear strength load down the slope,for the presence of complex surface and buried morphologies.Topographic irregularities generate maximum effects of waves amplification linked to wavelengths comparable to the horizontal dimension of the topographic feature.For this reason,the selected time-histories represent an appropriate input for the two-dimensional numerical response analyses when a dynamic phenomenon produce the resonant motion of a whole mountain.This represents an important earthquake-induced hazard in snow-covered mountain areas with high probability of seismic events.Some valleys are located in regions with scare ground motion data and investments on infrastructures are not always accompanied by adequate protection against earthquake-induced avalanches.The paper points out a simple deterministic approach for selecting a set of real accelerograms applied to a real case of Siella Mountain(Central Italy)where a large avalanche destroying a tourist facility of Rigopiano resort on 18 January 2017.The selected time histories were used as input for the two-dimensional numerical model of the subsoil to evaluate the topographic seismic amplification in ridge and compare it with the results of other authors.These methods suggest that morphology-related inertial effects should be considered as an overload action on snow layers when controlling multi-hazard studies and spatial planning.
基金Supported by Shanghai Natural Science Foundation(22ZR1472600).
文摘The development of InGaAs/InP single-photon avalanche photodiodes(SPADs)necessitates the utiliza-tion of a two-element diffusion technique to achieve accurate manipulation of the multiplication width and the dis-tribution of its electric field.Regarding the issue of accurately predicting the depth of diffusion in InGaAs/InP SPAD,simulation analysis and device development were carried out,focusing on the dual diffusion behavior of zinc atoms.A formula of X_(j)=k√t-t_(0)+c to quantitatively predict the diffusion depth is obtained by fitting the simulated twice-diffusion depths based on a two-dimensional(2D)model.The 2D impurity morphologies and the one-dimensional impurity profiles for the dual-diffused region are characterized by using scanning electron micros-copy and secondary ion mass spectrometry as a function of the diffusion depth,respectively.InGaAs/InP SPAD devices with different dual-diffusion conditions are also fabricated,which show breakdown behaviors well consis-tent with the simulated results under the same junction geometries.The dark count rate(DCR)of the device de-creased as the multiplication width increased,as indicated by the results.DCRs of 2×10^(6),1×10^(5),4×10^(4),and 2×10^(4) were achieved at temperatures of 300 K,273 K,263 K,and 253 K,respectively,with a bias voltage of 3 V,when the multiplication width was 1.5µm.These results demonstrate an effective prediction route for accu-rately controlling the dual-diffused zinc junction geometry in InP-based planar device processing.
基金The authors are thankful for support from NASA Award 80NSSC22K0100U.S.Department of Energy Computational Science Graduate Fellowship under Award Number DESC0022158+1 种基金Computational resources were provided by Extreme Science and Engineering Discovery Environment(XSEDE),which is supported by National Science Foundation grant number ACI-1053575This research used resources of the National Energy Research Scientific Computing Center(NERSC),a Department of Energy Office of Science User Facility using NERSC award ASCRERCAP0026889.
文摘Stagnant lid planets are characterized by a globe-encircling,conducting lid that is thick and strong,which leads to reduced global surface heat flows.Consequently,the mantles of such planets can have warmer interiors than Earth,and interestingly,a pyrolitic mantle composition under warmer conditions is predicted to have a distinctly different mantle transition zone compared to the present-day Earth(Hirose,2002;Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014;Dannberg et al,2022).Instead of olivine primarily transforming into its higher-pressure polymorphs such as wadsleyite and then ringwoodite,at pressures corresponding to 410 km and 520 km depth in Earth,respectively,it instead transforms into a mineral assemblage of wadsleyite,majorite,and ferropericlase(WMF),and then to majorite+ferropericlase(MF),before finally transforming into bridgmanite at pressures corresponding to 660 km depth in Earth(Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014).Convective motions in stagnant lid planets are dominated by small-scale instabilities(cold drips)forming within the mobile rheological sublayer under the rigid lid.Using ASPECT and a thermodynamic model of a pyrolitic mantle composition generated by HeFESTo,we show that under certain conditions,the small drips can pond atop the WMF-MF mineral phase transition.The barrier to convective flow arises from the WMF mineral phase assemblage having an effective negative thermal expansivity(Stixrude and Lithgow-Bertelloni,2022).Although large-scale downwellings that typically occur within mobile lid planets are able to pass through the WMF zone without difficulty(Dannberg et al.,2022;Li RP et al.,2024),the smaller and less negatively buoyant nature of downwelling drips in stagnant lid planets are more susceptible to these effects,which leads to an ephemeral layering of the mantle.Our numerical models show that in stagnant lid planets with mantle potential temperatures that exceed 1900 K,the smaller,cold drips from the lid continue to pile up until enough of them have coalesced that they collectively avalanche as a larger instability into the deeper interior.
基金supported by the Open Project of the Xinjiang Uygur Autonomous Region Key Laboratory(2017D04010).
文摘Snow avalanches are a common natural hazard in many countries with seasonally snow-covered mountains.The avalanche hazard varies with snow avalanche type in different snow climate regions and at different times.The ability to understand the characteristics of avalanche activity and hazards of different snow avalanche types is a prerequisite for improving avalanche disaster management in the mid-altitude region of the Central Tianshan Mountains.In this study,we collected data related to avalanche,snowpack,and meteorology during four snow seasons(from 2015 to 2019),and analysed the characteristics and hazards of different types of avalanches.The snow climate of the mid-altitude region of the Central Tianshan Mountains was examined using a snow climate classification scheme,and the results showed that the mountain range has a continental snow climate.To quantify the hazards of different types of avalanches and describe their situation over time in the continental snow climate region,this study used the avalanche hazard degree to assess the hazards of four types of avalanches,i.e.,full-depth dry snow avalanches,full-depth wet snow avalanches,surface-layer dry snow avalanches,and surface-layer wet snow avalanches.The results indicated that surface-layer dry snow avalanches were characterized by large sizes and high release frequencies,which made them having the highest avalanche hazard degree in the Central Tianshan Mountains with a continental snow climate.The overall avalanche hazard showed a single peak pattern over time during the snow season,and the greatest hazard occurred in the second half of February when the snowpack was deep and the temperature increased.This study can help the disaster and emergency management departments rationally arrange avalanche relief resources and develop avalanche prevention strategies.
文摘The avalanche warning service was established within the operational European territorial cooperation program Slovenia-Austria （SI-AT） 2007-2013 project ＂Natural Hazards without Frontiers＂. Four institutes, two from Austria and two from Slovenia, work together to publish an avalanche report during the winter season. The first regular season was the winter 2012/2013. The avalanche and the slab avalanche situation in the transnational area along the 160 km border between the south of Austria and north of Slovenia show major differences of avalanche building weather situations. Because of the nearby sea in the southwest of Slovenia, the prevailing weather situations for high precipitation are coming from southwest or southeast. Nevertheless sometimes a lot of fresh snow occurs at northerly weather situations, which is unusual for Slovenian Alps and is therefore poorly forecasted for this region. Austrian avalanche experts are facing the same problems at southerly weather situations. Hence, an exchange of experience, weather data as well as model information improves the avalanche warning on both sides of the Austrian-Slovenian border.
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.
基金financially supported by the National Natural Science Foundation of China(grant numbers 4167020392)the State Key Laboratory Foundation of Geohazard Prevention and Geoenvironment Protection(SKLGP2018K015)the Geological Investigation Project fromChina Geological Survey(DD20160336)
文摘Analyzing large prehistoric rock avalanches provides significant data for evaluating the disaster posed by these relatively infrequent but destructive geological events. This paper attempts to study the characteristics and dynamics of the Ganqiuchi granitic rock avalanche, in the middle of the northern margin of Qinling Mountains, 30 km to the south of Xi’an, Shaanxi Province, China. In plane view, this rock avalanche is characterized by source area, accumulation area and dammed lake area. Based on previous studies, historical records and regional geological data, the major trigger of the Ganqiuchi rock avalanche is considered to be a strong paleo-earthquake with tremendous energy. The in situ deposit block size distributions of the intact rock mass and the debris deposits are presented and analyzed by using a simple model for estimating the number of fragmentation cycles that the blocks underwent. The results show that the primary controlling factor of the fragmentation process is the pre-existing fractures, and there is a relationship between the potential energy and the fragmentation energy: the latter is approximately 20% of the former. Based on the dynamic discrete element technique, the study proposes a four-stage model for the dynamic course of the Ganqiuchi rock avalanche:(1) failing;(2) highspeed sliding;(3) collision with obstacles;(4) decelerated sliding, which has implication for hazard assessment of the potential rock avalanches in China and other countries with similar geological setting.
文摘A set of detected avalanches from January to April 2012 on a hillside southeast of lschgl, Austria is given. The avalanches are off-the-cut or caused by blast. The meteorological data of two monitoring stations nearby the hillside are taken for analysing the weather situation. The meteorological parameters air temperature, wind intensity and wind speed, relative humidity, precipitation and snow depth are investigated for similarities short before and during an avalanche. The avalanches are grouped into three categories and meteorological characteristics are found for each category. Thereby the avalanche hazard for the observed hillside is better assessed and an infrastructure safety by avalanche control due to concerted avalanche blasts is more effective. The result of the analysis shows three kinds of hazard weather conditions, which increase the avalanche hazard： warm air temperatures cause a settlement of the snow pack, but in the beginning of the process a weakening in the snow pack happens. Rapidly decreasing of the air temperature cause cracks in the snow pack and the combination of fresh snow and strong wind speed leads to accumulation of snow on sheltered slopes.
