Distribution and Susceptibility Assessment of Collapses and Landslides in the Riparian Zone of the Xiaowan Reservoir

The southwest alpine gorge region is the major state base of hydropower energy development in China and hence planned many cascading hydropower stations. After the reservoir impoundment, the intense water level fluctuations under the interaction of cascade dams operating and the mountainous flooding, usually cause bank collapse, landslide and debris flow hazards. The Xiaowan reservoir(XWR), for example, as the ‘dragon head' meg reservoir located in the middle mainstream of Lancang River, have resulted in a series of geohazards during its building and operating. In this study, we investigated the number and surface area of collapses and landslides(CLs) occurred in the water level fluctuations zone(WLFZ) of XWR using remote sensing images of Gaofen-1 and Google Earth; evaluated the CLs susceptibility using information value method. The results presented that the total WLFZ area of 87.03 km2 and 804 CLs masses with a total area of 1.98 km2 were identified in the riparian zone of XWR. CLs mainly occurred at an elevation of 1190–1240 m, and the CLs density increased with an increase in altitude. The WLFZ with a slope gradient of 25°– 45° is the main CLs distribution area that accounts for more than half of the total CLs area. The susceptibility assessment revealed that high and very high susceptibility zones are generally distributed along zones with an elevation of 1210–1240 m, a slope degree of 25°–45° and a slope aspect perpendicular to the direction of Lancang River. Furthermore, these susceptible zones are close in distance to the dam site and tend to be in the riparian zones with the formation lithology of Silurian strata. These results provide a valuable contribution to prevent and control geohazards in the XWR area. Moreover, this study offers a constructive sample of geohazards assessment in the riparian zone of large reservoirs throughout the mountains of southwest China.

Channelized and unchannelized collapses of granular columns on a horizontal surface

Columnar dangerous rock mass is widely developed in many high and steep mountain areas around the world.It often collapses,disintegrates and produces debris flow,which is disastrous.The collapse process of the columnar dangerous rock mass is very similar to the collapse of granular column.In this paper,we report the results of an experimental investigation of the flow induced by the collapse of a column of granular material over a horizontal surface.Two different setups are used,namely,a channelized granular column collapse(i.e.,two-dimensional) and an unchannelized granular column collapse(i.e.,three-dimensional),allowing us to compare channelized and unchannelized collapses flows.The experimental data suggest that our experimental findings were markedly different from those reported by previous authors(i.e.,include the channelized and unchannelized collapse flows showed differences in energy conversion and dissipation).In channelized collapse flows,the maximum vertical speed appears in the free fall regime,while,the maximum speed in the vertical direction of unchannelized collapse flows appears in the spreading regime.During the whole collapse process,i.e.,in channelized and unchannelized collapse flows,the conversion of potential energy and kinetic energy does not occur uniformly,and the maximum kinetic energy of the channelized collapse flows is higher than that of the unchannelized collapse flows,and compared with the unchannelized collapse flows,the dissipation energy in the channelized collapse flows is lower.A series of experiments was performed to predict the behaviour of different granular columns(characterized by different initial aspect ratio(a),varying from 1 to 4).The data obtained from 2 D experimental model and3 D experimental model have certain amount of difference,such as the particle runout distance(d1),the maximum central height(h2),and the deposition angle(i.e.,β1,β2).These differences show that the 2 D experimental model does not fully represent the 3 D conditions(i.e.,the role of side-walls on the channelized collapse flows characteristic is nonnegligible).Accordingly,care must be taken when validating 3 D models with 2 D experimental data.The movement of the tower dangerous rock masses with collapse failure mode could be evaluated using this channelized and unchannelized granular column experimental results.

Wave function collapses and 1/n energy spectrum induced by a Coulomb potential in a one-dimensional flat band system

We investigate the bound state problem in a one-dimensional flat band system with a Coulomb potential.It is found that,in the presence of a Coulomb potential of type I(with three equal diagonal elements),similarly to that in the twodimensional case,the flat band could not survive.At the same time,the flat band states are transformed into localized states with a logarithmic singularity near the center position.In addition,the wave function near the origin would collapse for an arbitrarily weak Coulomb potential.Due to the wave function collapses,the eigen-energies for a shifted Coulomb potential depend sensitively on the cut-off parameter.For a Coulomb potential of type II,there exist infinite bound states that are generated from the flat band.Furthermore,when the bound state energy is very near the flat band,the energy is inversely proportional to the natural number,e.g.,E_(n)∝1/n,n=1,2,3,...It is expected that the 1/n energy spectrum could be observed experimentally in the near future.

Population collapses in the pre-modern period:case study of the Fuping County, Northwest China

The pre-modern history of population change in the Fuping County(Shaanxi Province, China)during the Ming and Qing Dynasties(AD 1368-1911) was reconstructed using historical sources.The Fuping County experienced two major population collapses, i.e. the late Ming Dynasty(1550-1640 s) and the 1860-1880 s. The first one was caused by the great AD 1556 earthquake and the extreme droughts and warfare in the 1630-1640 s. The second one was caused by warfare and extreme droughts. As a whole, natural disasters, including extreme drought and great earthquake, were the key direct causes of population collapse, and climatic cooling would be a potential indirect cause. It is very interesting that population collapses occurred almost synchronously in the Fuping County and whole China, and the trends of population change were also very similar. Climate-population relationship in China would be valid at finer geographic level,and climatic cooling could be a potential indirect cause of population collapse.

Characteristics of Collapses Caused by the M8.1 Earthquake West of the Kunlun Mountains Pass

An M 8.1 earthquake that occurred west of the Kunlun Mountains Pass has caused more than 20 collapse bodies or zones, which are mainly distributed near the surface seismic rupture zone, west of Hoh Sai Lake. The collapses are of four types, bedrock, soil mass and ice mass collapses and avalanches. The spatial distribution and the characteristics of development of the collapses are analyzed in the paper. Comparised with those caused by other earthquakes, the collapses are smaller in scale. In addition to the lithological characteristics of the crustal media, topographic, geomorphic and climatic factors, weaker seismic ground motion is an important cause for formation of the smaller-scale collapses. The long surface rupture zone and weaker ground motion are important features of the seismic rupture, which may be related to the structure of the preexisting fault.

A Contribution to Analysis of Collapse of High-Rise Building Inspired by the Collapses of WTC1 and WTC2: Derivation of Simple Formulas for Collapse Upper Speed and Acceleration

The paper is a contribution to the technical discussion concerning the collapses of the WTC buildings. It returns to the problem of the dynamics of the collapses;it does not concern the reason why the buildings started collapsing, but investigates the dynamics of the collapse itself. It works with the same assumptions as the official NIST report [1], i.e. that the falling mass hits the motionless mass beneath;the supporting columns loose stability and the mass of the pertinent floor starts to fall together with the falling mass. The aim was to derive the theoretical upper limit of the speed of the collapse, supposing that influence of the columns which resist the fall, is neglected. The differential equation of the fall was obtained using two independent laws of mechanics, with the identical result. Its solution can be found from a very simple explicit formula. The theoretical upper limit acceleration of the fall obtained by such formula is one third of the gravitational acceleration, which is faster than it was observed in the case of the collapses of WTC1 and WTC2. This leads to the conclusion that the mechanism of the collapse must be different from the assumed and the falling mass must not hit the motionless mass bellow it, but rather a mass which had started to fall before the impact of the falling mass occurred.

Centennial-scale monsoon collapses during Marine Isotope Stage(MIS)7e detected in a northern Chinese stalagmite record

Occurrence or absence of centennial-scale climatic variability during Marine Isotope Stage(MIS)7e,the first peak interval of the Penultimate Interglacial,remains ambiguous due to the limited available high-resolved records.Here,we present a decadal-resolved stalagmiteδ^(18)O record from northern China spanning from 242.3 to 236.8 ka BP,covering MIS7e.The composite KLSδ^(18)O record,integrating this study with the previous record in the same cave,shows a descending trend from TerminationⅢto MIS7e,which follows the increasing Northern Hemisphere summer insolation(NHSI).This observation further emphasizes the important influence of NHSI on the glacial/interglacial transition.There are more large-amplitude,millennial-to centennial-scale variability occurring during TerminationⅢcompared with MIS7e,implying that ice-sheet decay potentially plays an important role in climatic excursions.Four centennial-scale summer monsoon collapses,peaking at~242.1,~240.8,~239.3 and~238.2 ka BP,are detected in our new record,indicating the pervasiveness of the intra-interglacial climatic instability.Given the lack of solar activity and freshwater outbursts data during MIS7e,it is not possible to conclude about the drivers of the identified abrupt climatic anomalous.Following the dynamic mechanisms of sub-millennial climatic anomalous during early Holocene,we tentatively propose that slowdown of the meridional overturning circulation caused by freshwater fluxes into North Atlantic and/or attenuated solar irradiance is the potential forcing for the abrupt climate events within MIS7e.Additionally,attenuated solar irradiance could also result in climatic anomalies through low-latitude processes.

An improved ASM-HEMT model for kink effect on GaN devices

With the analysis of experiment and theory on GaN HEMT devices under DC sweep,an improved model for kink effect based on advanced SPICE model for high electron mobility transistors(ASM-HEMT)is pro⁃posed,considering the relationship between the drain/gate-source voltage and kink effect.The improved model can not only accurately describe the trend of the drain-source current with the current collapse and kink effect,but also precisely fit different values of drain-source voltages at which the kink effect occurs under different gatesource voltages.Furthermore,it well characterizes the DC characteristics of GaN devices in the full operating range,with the fitting error less than 3%.To further verify the accuracy and convergence of the improved model,a load-pull system is built in ADS.The simulated result shows that although both the original ASM-HEMT and the improved model predict the output power for the maximum power matching of GaN devices well,the im⁃proved model predicts the power-added efficiency for the maximum efficiency matching more accurately,with 4%improved.

A tendon system to re-center steel moment frames with weak stories

A wide open bottom story of a frame building is often expected by owners for use as a garage or shops.However,this leads to weak stories due to abrupt changes in lateral stiffness and often results in unexpected story collapse as observed in many previous earthquakes.To retrofit frame buildings that have experienced weak story damage,a tendon system is proposed in this study,which consists of a set of swaying columns and tendons.The swaying columns are used to uniformly redistribute the lateral deformation along the height,while the tendons provide extra lateral stiffness and renders the entire structural system a re-centering capability.To avoid unnecessary forces to swaying columns,pin-connections are used at the bottom.Tendons are placed over the entire story to gain large elastic displacements.Parametric analysis reveals that the swaying column,with a stiffness of about 0.9 times that of the weak story,and the tendons attached at the roof,with a stiffness of 0.04 times that of the weak story,can provide the optimal performance with a maximum residual story drift angle of less than 0.5%.Online hybrid tests were carried out,which demonstrated that uniformly distributed story drifts and acceptable residual deformation could be achieved by the proposed tendon system.

Mobility and dynamic erosion process of granular flow:insights from numerical investigation using material point method

In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular flow.An index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of friction.The index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction weakening.An increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular flow.The mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular soil.However,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on gravity.The mobility of granular flow increases gradually by lowering the indexes of the apparent and repose coefficients of friction of granular flow while changing the surroundings,in turn,the dry soil,submerged soil and saturated soil,implying a gradually increased excessive mobility of granular flow with the friction weakening of granular soil.Presence of water in granular flow may be a potential catalyzer to yield a long run-out granular flow,as revealed in comparison of water-absent and water-present granular flows.In addition,the dynamic erosion and entrainment of based soil induced by granular flow subjected to the complex geological settings,i.e.,the aspect ratio,granular mass,gravity,friction and dilatancy resistance,and presence of water,were comprehensively investigated as well.

Analysis of mechanical strengths of extreme line casing joint considering geometric, material, and contact nonlinearities

To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.

Roof collapse mechanism of weak surrounding rock for deep-buried tunnels under high geostress conditions

High geostress,a typical attribute of tunnels located at significant depths,is crucial in causing stress-induced failure and influencing the stability of the tunnel crown.This study developed an analytical method for the failure mechanism that occurs in deep-buried tunnel roofs,taking into account the influence of geostress.The limit analysis theory was utilized for deriving analytical solutions about the geometry of the collapsing surface and the limit supporting pressure.The collapsing surface obtained by the analytical solution was validated by the findings of the physical model test,which shows a high level of agreement with the actual one.An extensive investigation was done to explore the effects of the lateral pressure coefficients,the tunnel buried depth,the geological conditions of the surrounding rock,the long-short axis ratio,and the size of the tunnel profile.The findings indicate that an increase in the lateral pressure coefficient from 0.5 to 1.5 results in a reduction in the height of the collapsing zone by 2.08 m and the width of the collapsing zone by 1.15 m,while simultaneously increases the limit supporting pressure by 18.9%.The proposed upper bound method accurately determines the limit supporting pressure and the geometry of the collapsing surface,which aligns well with the results acquired through numerical modelling and on-site monitoring in actual engineering applications.The proposed analytical method can serve as a reference for similar crown failure issues of deep-buried tunnels.

Granular collapse in fluids:Dynamics and flow regime identification

The collapse of granular material in fluids is a prevalent phenomenon in both natural and industrial processes,displaying a notable sensitivity to initial configuration of the system.This study is specifically oriented towards falling process of collapsing material under various fluid conditions,employing the computational fluid dynamics-discrete element method(CFD-DEM)to primarily investigate the dynamics and scaling laws of deposit morphology of collapsed material.Through a comprehensive analysis of particle sedimentation in fluids,we introduce a refined inertial characteristic time for granular collapse within the inertial regime.Subsequently,we propose modifications to conventional fluid-particle density ratio and Reynolds number,aiming to enhance the accuracy of depicting collapse dynamics and identifying flow regimes across diverse column heights and fluid conditions.Finally,we construct a phase diagram of flow regimes using modified dimensionless numbers,emphasizing the role of column height in transition between viscous and inertial regimes.These parameters demonstrate enhanced relevance in governing the collapse of immersed granular columns,thereby contributing to a more nuanced understanding of fluid-particle interations in dense granular flows under different regimes.

Early Devonian Post-collisional Granitic Magmatism in the North Qilian Orogenic Belt,Western China:Insights into Lithospheric Delamination and Orogenic Collapse

Post-collisional magmatism contains important clues for understanding the reworking and growth of continental crust,as well as lithospheric delamination and orogenic collapse.Early Devonian magmatism has been identified in the North Qilian Orogenic Belt(NQOB).This paper reports an integrated study of petrology,whole-rock geochemistry,Sm-Nd isotope and zircon U-Pb dating,as well as Lu-Hf isotopic data,for two Early Devonian intrusive plutons.The Yongchang and Chijin granites yield zircon U-Pb ages of 394-407 Ma and 414 Ma,respectively.Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium-rich minerals,LREE-enriched patterns with negative Eu anomalies and a negative correlation between P_(2)O_(5) and SiO_(2) contents,consistent with geochemical features of I-type granitoids.Zircons from the studied granites display negative to weak positive ε_(Hf)(t)values(−5.7 to 2.1),which agree well with those of negative ε_(Nd)(t)values(−6.4 to−2.9)for the whole-rock samples,indicating that they were derived from the partial melting of Mesoproterozoic crust.Furthermore,low Sr/Y ratios(1.13-21.28)and high zircon saturation temperatures(745℃ to 839℃,with the majority being>800℃)demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source.Taken together,the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle-derived magmas at high-temperature and low-pressure conditions during postcollisional extensional collapse.The data obtained in this study,when viewed in conjunction with previous studies,provides more information about the tectonic processes that followed the closure of the North Qilian Ocean.The tectonic transition from continental collision to post-collisional delamination could be constrained to~430 Ma,which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon ε_(Hf)(t)values for granitoids.A two-stage tectonic evolution model from continental collision to post-collisional extensional collapse for the NQOB includes(a)continental collision and crustal thickening during ca.455-430 Ma,characterized by granulite-facies metamorphism and widespread low-Mg adakitic magmatism;(b)post-collisional delamination of thickened continental crust and extensional collapse of orogen during ca.430-390 Ma,provided by coeval high-Mg adakitic magmatism,A-type granites and I-type granitoids with low Sr-Y ratios.

Airblast evolution initiated by Wangjiayan landslides in the M_(s)8.0 Wenchuan earthquake and its destructive capacity analysis

Airblasts,as one common phenomenon accompanied by rapid movements of landslides or rock/snow avalanches,commonly result in catastrophic damages and are attracting more and more scientific attention.To quantitatively analyze the intensity of airblast initiated by landslides,the Wangjiayan landslide,occurred in the Wenchuan earthquake,is selected here with the landslide propagation and airblast evolution being studied using FLUENT by introducing the Voellmy rheological law.The results reveal that:(1)For the Wangjiayan landslide,its whole travelling duration is only 12 s with its maximum velocity reaching 36 m/s at t=10 s;(2)corresponding to the landslide propagation,the maximum velocity,28 m/s,of the airblast initiated by the landslide also appears at t=10 s with its maximum pressure reaching594.8 Pa,which is equivalent to violent storm;(3)under the attack of airblast,the load suffered by buildings in the airblast zone increases to 1300 Pa at t=9.4 s and sharply decreased to-7000 Pa as the rapid decrease of the velocity of the sliding mass at t=10 s,which is seriously unfavorable for buildings and might be the key reason for the destructive collapse of buildings in the airblast zone of the Wangjiayan landslide.

Collapse Behavior of Pipe-Framed Greenhouses with and without Reinforcement under Snow Loading:A 3-D Finite Element Analysis

The present paper first investigates the collapse behavior of a conventional pipe-framed greenhouse under snow loading based on a 3-D finite element analysis,in which both geometrical and material non-linearities are considered.Three snow load distribution patterns related to the wind-driven snow particle movement are used in the analysis.It is found that snow load distribution affects the deformation and collapse behavior of the pipe-framed greenhouse significantly.The results obtained in this study are consistent with the actual damage observed.Next,discussion is made of the effects of reinforcements by adding members to the basic frame on the strength of the whole structure,in which seven kinds of reinforcement methods are examined.A buckling analysis is also carried out.The results indicate that the most effective reinforcement method depends on the snow load distribution pattern.

Progressive Collapse Resistance of a New Staggered Story Isolated System

A new staggered isolated system developed from the mid-story isolated system is the new staggered story isolated system. There are not many studies on this structure currently. In this study, an 18-story new staggered story isolated system model is established using SAP2000. The dynamic nonlinear dynamic alternate method is used to analyze the structure against progressive collapse. Results show that the structure has good resistance to progressive collapse, and there is no progressive collapse under each working condition. The progressive collapse does not occur for the case of removing only one vertical structural member of the new staggered of isolated system. The side column has big influence on this isolated structures’ progressive collapse;the removal of vertical structural member of the isolation layer has less impact on the structure than the removal of the bottom vertical structural member. After the removing of the member, the internal force of the structure will be redistributed, and the axial force of the adjacent columns will change obviously, showing a trend of “near large and far small”.

Swift XRT Analysis of Type II-P Supernova SN 2008ij

This study investigates the X-ray properties and evolution of Type II supernovae (SNe II) observed by Swift, examining variations among supernovae and exploring their X-ray characteristics over time. We present the first X-ray study of the Type IIp supernova SN 2008ij using data from the Swift X-ray mission. This investigation focuses on its spectral properties, identifying an X-ray flux of 1.20 (+0.11, −0.10) × 10−13 erg/cm2/s and a plasma temperature of 4.76 (+1.22, −0.83) keV. Our study marks an advancement in understanding SN 2008ij, providing crucial results into its X-ray emission characteristics. These results lay the groundwork for future studies of Type IIp supernovae, offering a foundation for exploring their evolutionary and physical processes.

Fluctuation assisted collapses of Bose-Einstein condensates

We study the collapse dynamics of a Bose-Einstein condensate subjected to a sudden change of the scattering length to a negative value by adopting the self-consistent Gaussian state theory for mixed states.Compared to the Gross-Pitaevskii and the Hartree-Fock-Bogoliubov approaches,both fluctuations and three-body loss are properly treated in our theory.We find a new type of collapse assisted by fluctuations that amplify the attractive interaction between atoms.Moreover,the calculation of the fluctuated atoms,the entropy,and the second-order correlation function showed that the collapsed gas significantly deviated from a pure state.

Relationship between gravitational flap structures in the backlimb of anticlinal breakthrough Fault-Propagation Folds:case study of the Southern-Central Tunisian Atlas

The development of orogenic belts structures in the Southern-Central Tunisian Atlas is influenced by the evolution of tectonic activities during different phases,which are also closely linked to the formation of gravitational collapse structure.The typical example is that of the northern flank of the Jebel Orbata particularly the Ben Zannouch fold.It is an asymmetrical anticline interpreted by the model of“Fault Propagation Folds”.The development of the Ben Zannouch structures is resulted from landslides,scree falls and inverted layers plunging to the south.The direction of resulted gravitational structure is parallel to the main thrust direction of the Bou Omrane anticline.The thrust activity of Bou Omrane fault is associated to the important paleo-slope facing south and plastic lithology(incompetent marl layers)of outcropped series,facilitates the development of the Ben Zannouch Flap structure.The definition of gravitational collapse structures for the first time in Tunisia particularly in the northern flank of the Jebel Orbata is controlled by many principal structural conditions:fragmentation of the landslide surfaces,rheology and topography.Other regional factors can be distinguished in the Southern-Central Tunisian Atlas as the seismic activity of the pre-existing Gafsa fault reactivated during compressive phases and the weather conditions during the postglacial period.