Advances in ice avalanches on the Tibetan Plateau

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.

Evidence of ancient rock-ice avalanches along the China-Bhutan Chomolhari Range,and their implications for demise of the summit

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.

Mantle avalanches in a Venus-like stagnant lid planet

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.

Numerical investigation of effects of “baffles-deceleration strip” hybrid system on rock avalanches

Arrays of baffles are usually installed in front of protection site to attenuate the flow energy of rock avalanches in mountainous areas. Optimization design is crucial for efficiency promotion in hazard energy dissipation engineering. In this study, a deceleration strip was added in the baffles protection system to optimize the traditional baffles system. The effects of the "baffles-deceleration strip" hybrid protection system was discussed in detail with the nails number and nails angle. This study presents details of numerical experiments using the discreteelement method(DEM). The effect of the optimization of hybrid protection system(nail angle and nail number) were investigated specifically, especially the impact force that avalanches exerted on structures. The results show that the maximum impact forces and kinetic energy of the rock avalanches decreases with the increase of the number and angle of the nail. Moreover, the distance between the toe and the bearing structure(L_m) is also a key factor. The shorter the distance L_m(30 m) is, the higher the maximum impact force are. The longer the distance L_m(70 m) is, the lower the maximum impact force are. Under the same size of the nails, increasing the numbers can enhance the dissipation ability of the hybrid protection system. Meanwhile, increasing itsangle can also enhance the dissipation ability. There are three key ways for nails attenuate rock avalanches:(i) block the fine particles directly;(ii) form the particles bridge between nails and baffles;(iii) dissipate the coarse particles energy directly. The effect of segregation in rock avalanches is crucial for the energy dissipation mechanism, which is a key factor to optimize the traditional baffle system.

Analysis of Detected Avalanches Using Meteorological Data of Nearby Monitoring Stations in Ischgl, Austria

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.

The Production of Patents and Evolution of the Production of Knowledge around Snow Avalanches

Scientific research on snow avalanches is relatively modem, yet in constant and rapid evolution, as the multiple disciplines involved in its development will, in turn, become more specialized and more technical. Patents are part of research and knowledge production. The scientific community and policy makers are increasingly interested in production of knowledge collaboratively. Almost all of the research being conducted on snow avalanches uses technology, technique or instrumentation. One main objective of this study is to draw from the literature the many technologies, techniques and instrumentations that are being used in research related to avalanches. Thus, a textual analysis of the most significant literature in the field of snow avalanches was done. In this analysis, techniques, technologies and instrumentations have emerged. A patent search has been done in databases. Subsequently, patents were conceptualized. The proportion of applicants for patents is higher in industry than in universities. The measure of exploration of the ongoing sociocognitive transformations of science and technology systems presents a useful tool to conduct a study to explore these transformations. It would be interesting for the scientific community, but also for the industry, to elaborate concept mapping when applied to avalanche research, which would help in determining referents.

Numerical simulation for the initial state of avalanche in polydisperse 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.

Dynamic Characteristics of the Long Runout Rock-ice Avalanche at High Altitude——A Case from the Zelongnong Basin,Eastern Himalayan Syntaxis,China

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.

Topographic seismic effects and avalanche hazard:A case study of Mount Siella(L’Aquila,Central Italy)

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.

Protective effect of retaining wall on rock avalanche:A case study of Nayong rock avalanche in China

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.

基于RAMMS-AVALANCHE模型的雪崩模拟参数敏感性分析

以巩乃斯大陆性气候雪崩危险区为研究背景,建立三维数字地形模型对雪崩运动过程进行模拟。研究RAMMS雪崩数值模拟结果的影响因素,分析计算网格分辨率、雪层断裂深度、摩擦系数3种参数值对模拟结果的影响程度及敏感性。通过单因素分析法对比不同参数下模拟结果进而得出3种参数的影响程度,采用灰色关联法分析参数对模拟结果的敏感性。结果表明:选择合适的计算网格分辨率能提高模拟结果的准确性;雪层断裂深度每减少10%,流动高度变化率在5%~7%;流动速度变化率在1%~2%;冲击力变化率在2%~3%;而摩擦系数的大小主要对堆积区特征值和雪崩停止时间产生较大影响,对运动过程中的特征值影响较小。在此基础上进行敏感度计算,根据计算结果确定各特征值最大影响性时参数的主次关系。研究结果明晰了雪崩模拟各输入参数的敏感性,可有效提高雪崩数值模拟参数选取的合理性和计算结果的准确性,为雪崩灾害危险程度分析提供依据。

A New Method to Investigate InGaAsP Single-Photon Avalanche Diodes Using a Digital Sampling Oscilloscope

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.

满足严格Avalanche标准的布尔函数的性质

本文讨论了满足严格Ａｖａｌａｎｃｈｅ标准的布尔函数的一个必要条件；对满足（ｎ—３）阶严格的Ａｖａｌａｎｃｈｅ标准（ＳＡＣ）的布尔函数，和所有次数不超过二次的满足任意阶严格Ａｖｌａｎｃｈｅ标准的布尔函数，本文给出了它们的布尔多项式特征．ＷａｎｇＪｉａｎｙｕ（Ｄｅｐｔ．ｏｆＭａｔｈ．，ＮａｎｋａｉＵｎｉｖｅｒｓｉｔｙ，Ｔｉａｎｊｉｎ３０００７１）是ｎ元布尔函数，则易证明ｆ（ｘ）满足ＳＡＣ的充要条件是每一个ｆｉ（ｘ）均满足ＳＡＣ（１≤ｉ≤ｍ）。定义２称ｆ满足ｍ阶严格Ａｖａｌａｎｃｈｅ标准（ＳＡＣ）（１≤ｍ≤ｎ－２），如果ｆ满足：任意选择ｆ的任意ｍ个变元的值后所得到的函数是满足ＳＡＣ的布尔函数。显然不可能存在满足（ｎ－ｌ）阶ＳＡＣ的函数，因为任意确定ｆ的任意确定（ｎ－１）个变元的取值以后所得到的函数是仿射函数，它不可能满足ＳＡＣ因此次数最高的ＳＡＣ是（ｎ－２）阶ＳＡＣ。实际上，文献［３］给出了所有满足（ｎ－２）阶ＳＡＣ的布尔函数的形式。定理１设，满足阶为（ｎ－２）的ＳＡＣ的充要条件是：里ａｉεＺ２，ｉ＝０，１，…，ｎ。因此ｆ是（ｎ－２）阶ＳＡＣ的布尔函数的充要条件是ｆ的次数为２，且二次项的系数均为１。下面将给出满足?

Recent progress of SiC UV single photon counting avalanche photodiodes

4H-SiC single photon counting avalanche photodiodes(SPADs)are prior devices for weak ultraviolet(UV)signal detection with the advantages of small size,low leakage current,high avalanche multiplication gain,and high quantum efficiency,which benefit from the large bandgap energy,high carrier drift velocity and excellent physical stability of 4 H-SiC semiconductor material.UV detectors are widely used in many key applications,such as missile plume detection,corona discharge,UV astronomy,and biological and chemical agent detection.In this paper,we will describe basic concepts and review recent results on device design,process development,and basic characterizations of 4 H-SiC avalanche photodiodes.Several promising device structures and uniformity of avalanche multiplication are discussed,which are important for achieving high performance of 4 HSiC UV SPADs.

Effects of high-energy proton irradiation on separate absorption and multiplication GaN avalanche photodiode

The effect of high-energy proton irradiation on GaN-based ultraviolet avalanche photodiodes(APDs) is investigated. The dark current of the GaN APD is calculated as a function of the proton energy and proton fluences. By considering the diffusion, generation–recombination, local hopping conductivity, band-to-band tunneling, and trap-assisted tunneling currents, we found that the dark current increases as the proton fluence increases, but decreases with increasing proton energy.

Characteristics and hazards of different snow avalanche types in a continental snow climate region in the Central Tianshan Mountains

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.

Dark count rate and band to band tunneling optimization for single photon avalanche diode topologies

This paper proposes two optimal designs of single photon avalanche diodes(SPADs) minimizing dark count rate(DCR). The first structure is introduced as p^+/pwell/nwell, in which a specific shallow pwell layer is added between p^+and nwell layers to decrease the electric field below a certain threshold. The simulation results show on average 19.7%and 8.5% reduction of p^+/nwell structure’s DCR comparing with similar previous structures in different operational excess bias and temperatures respectively. Moreover, a new structure is introduced as n+/nwell/pwell, in which a specific shallow nwell layer is added between n+and pwell layers to lower the electric field below a certain threshold. The simulation results show on average 29.2% and 5.5% decrement of p^+/nwell structure’s DCR comparing with similar previous structures in different operational excess bias and temperatures respectively. It is shown that in higher excess biases(about 6 volts), the n+/nwell/pwell structure is proper to be integrated as digital silicon photomultiplier(dSiPM) due to low DCR. On the other hand, the p^+/pwell/nwell structure is appropriate to be utilized in dSiPM in high temperatures(above 50?C) due to lower DCR value.

THE AVALANCHE DYNAMICS IN RANDOM NEAREST NEIGHBOR MODELS OF EVOLUTION WITH INTERACTION STRENGTH

A generalized Bak-Sneppen model （BS model） of biological evolution with intcraction strength θ is introduced in d-dimensional space, where the “nearest neighbors” are chosen among the 2d neighbors of the extremal site, with the probabilities rebated to the sizes of the fitnesses. Simulations of one- and two-dimensional models arc given.For given θ 〉 0, the model can self-organize, to a critical state, and the critical threshold fc（θ） decreases as θ increases. The exact gap equation depending on θ is presented, which reduces to the gap equation of BS model as θ tends to infinity. An exact cquation for the critical exponent γ（θ） is also obtained. Scaling relations are established among the six critical exponents of the avalanches of the model.

Discrete Element Modeling of Debris Avalanche Impact on Retaining Walls

In China,gravity retaining walls are widely used as protection structures against rockfalls,debris flows and debris avalanches along the roads in mountainous areas.In this paper,the Discrete Element Method(DEM) has been used to investigate the impact of granular avalanches and debris flows on retaining walls.The debris is modeled as two dimensional circular disks that interact through frictional sliding contacts.The basic equations that control the deformation and motion of the particles are introduced.A series of numerical experiments were conducted on an idealized debris slide impacting a retaining wall.The parametric study has been performed to examine the influences of slope geometry,travel distance of the sliding mass,wall position,and surface friction on the impact force exerted on the wall.Results show that:1) the force achieves its maximum value when slope angle is equal to 60°,as it varies from 30° to 75°;2) an approximate linear relationship between the impact force and the storage area length is determined.

Avalanche activity and characteristics of its triggering factors in the western Tianshan Mountains,China

Snow avalanche is a serious threat to the safety of roads in alpine mountains. In the western Tianshan Mountains, large scale avalanches occur every year and affect road safety. There is an urgent need to identify the characteristics of triggering factors for avalanche activity in this region to improve road safety and the management of natural hazards. Based on the observation of avalanche activity along the national road G218 in the western Tianshan Mountains, avalanche event data in combination with meteorological, snowpack and earthquake data were collected and analyzed. The snow climate of the mountain range was examined using a recently developed snow climate classification scheme, and triggering conditions of snow avalanche in different snow climate regions were compared. The results show that snowfall is the most common triggering factor for a natural avalanche and there is high probability of avalanche release with snowfall exceeding 20.4 mm during a snowfall period. Consecutive rise in temperature within three days and daily mean temperature reaching 0.5℃ in the following day imply a high probability of temperaturerise-triggered avalanche release. Earthquakes have a significant impact on the formation of large size avalanches in the area. For the period 2011-2017, five cases were identified as a consequence of earthquake with magnitudes of 3.3≤M_L≤5.1 and source-to-site distances of 19~139 km. The Tianshan Mountains are characterized by a continental snow climate with lower snow density, lower snow shear strength and high proportion depth hoar, which explains that both the snowfall and temperature for triggering avalanche release in the continental snow climate of the Tianshan Mountains are lower than that in maritime snow climate and transitional snow climate regions. The findings help forecast avalanche release for mitigating avalanche disaster and assessing the risk of avalanche disaster.