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Effects of water content on the shear behavior and critical state of glacial till in Tianmo gully of Tibet, China

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Journal of Mountain Science 2019年第8期16卷 1743-1759页

作者： zhou gordon g.d. CHEN Lei-lei MU Qing-yi CUI Kahlil Fredrick E. SONg.d.ng-ri Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences(CAS)Chengdu 610041China University of Chinese Academy of Sciences Beijing 100049China department of Civil Engineering Xi'an Jiaotong UniversityXi'an 710049China

glacial tills are widely distributed in Tibet, China, and are highly susceptible to landslides under intense rainfalls. Failures of the slope during rainfall are closely related to the shear behavior of glacial tills at different moisture conditions. This study investigates the shear behavior and critical state of saturated and unsaturated glacial tills through a series of drained direct shear tests. The tests were conducted on two types of compacted glacial tills with different water contents and total normal stresses. A strain softening mode of failure is observed for all water content conditions accompanied by noticeable dilation. dilatancy is found to decrease with increasing water content. Unsaturated samples showed increased rates of dilation as water content is decreased for all applied normal stresses a behavior which cannot be predicted well by classical stressdilatancy models. Furthermore, it was found that the Critical State Line(CSL), plotted on the(e-ln) plane, can be used to define the shear behavior of unsaturated glacial tills at different water *** CSL of saturated glacial tills run parallel to this line. The experimental results in this study are aimed to provide a basic understanding to the underlying failure mechanisms of glacial tills.

关键词： glacial till Shear behavior Water content dilatancy direct shear test Critical state

Velocity profiles and energy fluctuations in simple shear granular flows

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Particuology 2016年第4期14卷 80-87页

作者： Chuanqi Liu Qicheng Sun gordon g.d. zhou State Key Laboratory for Hydroscience and Engineering Tsinghua University Beijing 100084 China Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China

Rheology analysis of granular flows is important for predicting geophysical hazards and designing industrial processes. Using a discrete element method, we simulate simple shear flows in 3d under a constant confining pressure of 10 kPa. The inertial number proposed by the gdR Midi group in France is adopted to distinguish rheology regimes, Both translational and angular velocity profiles are investigated, and both fluid-like and solid-like behavior modes are observed in the flows. The maximum angular velocity occurs near the localized deformation area. We also investigate the energy characteristics of the flows and find that at very small shearing speed, the mean kinetic energy density ek is close to zero, while the mean elastic energy density ec is much greater. At large shearing speed, ek increases. The fluctuating parts of the two types of energy increase with increasing shear speed. Thus, the mean energy density ratio ek/ec can be used in addition to the inertial number to distinguish flow regimes. These results provide insights from energetics into the rheological properties of granular flows.

关键词： dense granular flows Simple shear Energy fluctuations

Simulations of granular flow along an inclined plane using the Savage-Hutter model

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Particuology 2012年第2期10卷 236-241页

作者： Minglong Fei Qicheng Sun deyu Zhong gordon g.d.zhou State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China

In this work a velocity-dependent friction is introduced into a depth-averag.d.5avage-Hutter dynamical model for shallow granular flows. The process of granular material flowing along an inclined plane and then depositing on a horizontal plane is simulated. The surface profiles and evolution of various types of energy are investigated and compared when using the standard Coulomb-type friction versus velocity- dependent friction. Interestingly, there is a small difference between the two different types of friction.

关键词： granular flowsdynamics frictionSavage-Flutter model

EXPERIMENTAL STUdY ON BEd RESISTANCE CHARACTERISTICS OF NONUNIFORM SEdIMENT

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Journal of Hydrodynamics 2000年第4期12卷 66-74页

作者： zhou, g.d. Liu, Q.Y. Wang, g.X. Hui, Y.J. Pang, d.M. Tsinghua Univ. Beijing 100084 China

Under natural circumstances, the bed of fluvial river is composed of nonuniform sediment, and its nonuniform property influences very much the bed resistance and flow characteristics. By using a one-dimensional laser velocimeter, flume experiments are carried out to analyze the resistance characteristics of open channel flow with the bed sediment composed of different representative particles and having.d.fferent nonuniform properties. By means of separating factors, the factors affecting the bed resistance, including particle diameter, nonuniform property and flow conditions, are studied. A great number of laboratory test results and field data from other investigators have been analyzed.

关键词： Sediments

Backward automatic calibration for three-dimensional landslide models

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geoscience Frontiers 2021年第1期12卷 231-241页

作者： giacomo Titti giulia Bossi gordon g.d.zhou gianluca Marcato Alessandro Pasuto dICAM-UNIBO Department of CivilChemicalEnvironmental and Materials EngineeringAlma Mater Studiorum University of BolognaViale Risorgimento 2Bologna40136Italy IRPI-CNR Research Institute for Geo-Hydrological ProtectionNational Research CouncilC.so Stati Uniti4Padova35127Italy IMHE-CAS Key Laboratory of Mountain Hazards and Earth Surface Process/Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesBlock 4Renminnanlu RoadChengdu610041China

Back-analysis is broadly used for approaching geotechnical problems when monitoring.d.ta are available and information about the soils properties is of poor *** landslide stability assessment back-analysis calibration is usually carried out by time consuming trial-and-error *** paper presents a new automatic decision Support System that supports the selection of the soil parameters for three-dimensional models of landslides based on monitoring *** method considering a pool of possible solutions,generated through permutation of soil parameters,selects the best ten configurations that are more congruent with the measured *** reduces the operator biases while on the other hand allows the operator to control each step of the *** final selection of the preferred solution among the ten best-fitting solutions is carried out by an *** operator control is necessary as he may include in the final decision process all the qualitative elements that cannot be included in a qualitative analysis but nevertheless characterize a landslide dynamic as a whole epistemological subject,for example on the base of geomorphological evidence.A landslide located in Northeast Italy has been selected as example for showing the system *** proposed method is straightforward,scalable and robust and could be useful for researchers and practitioners.

关键词： Automatic landslide modelling FLAC3d~(TM) Back-analysis Optimization decision Support System

debris flow impact on flexible barrier: effects of debrisbarrier stiffness and flow aspect ratio

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Journal of Mountain Science 2019年第7期16卷 1629-1645页

作者： SONg.d.ng-ri zhou gordon g.d.CHOI Clarence Edward ZHENg Yun Key Laboratory of Mountain Hazards and Earth Surface Process/Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China University of Chinese Academy of Sciences Beijing 100049China department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyClear Water BayKowloonHong Kong SARChina The HKUST Jockey Club Institute for Advanced Study Hong Kong SARChina

Conventionally,flexible barriers are rated based on their ability to resist a free-falling boulder with a particular input ***,there is still no well-accepted approach for evaluating performance of flexible barrier under debris flow *** this study,a large-nonlinear finite-element model was used to back-analyze centrifuge tests to discern the effects of impact material type,barrier stiffness,and flow aspect ratio(flow height to flow length)on the reaction force between the impacting medium and flexible *** show that,in contrast to flexible barriers for resisting rockfall,the normal impact force induced by the highly frictional and viscous debris is insensitive to barrier *** is because the elongated distributions of kinetic energy are mainly dissipated by the internal and boundary shearing,and only a small portion is forwarded to the ***,a new stiffness number is proposed to characterize the equivalent stiffness between a debris flow or a boulder,and a flexible *** the circumstance of an extremely elongated debris flow event,i.e.,low aspect ratio,the load on a barrier is dominated by the static component and thus not sensitive to the barrier stiffness.

关键词： debris flow Flexible barrier Impact Stiffness Flow aspect ratio

Experimental study of debris flow caused by domino failures of landslide dams

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International Journal of Sediment Research 2014年第3期29卷 414-422页

作者： Hua-Yong CHEN Peng CUI gordon g.d.zhou Xing-Hua ZHU Jin-Bo TANg Key Laboratory of Mountain Hazards and Earth Surface Process CAS Institute of Mountain Hazards and Environment CAS

The formation of landslide dams is often induced by earthquakes in mountainous *** failure of a landslide dam typically results in catastrophic flash floods or debris flows *** attention has been given to the processes and mechanisms involved in the failure of individual landslide ***,the processes leading to domino failures of multiple landslide dams remain *** this study,experimental tests were carried out to investigate the domino failure of landslide dams and the consequent enlargement of downstream debris *** blockage conditions were considered,including complete blockage,partial blockage and erodible bed(no blockage).The mean velocity of the flow front was estimated by *** stress transducers(TSTs)and Laser range finders(LRFs) were employed to measure the total stress and the depth of the flow front,*** a complete blockage pattern,a portion of the debris flow was trapped in front of each retained landslide dam before the latter collapsed *** was accompanied by a dramatic decrease in the mean velocity of the flow ***,under both partial blockage and erodible bed conditions,the mean velocity of the flow front increased gradually downward along the sloping *** failures of the landslide dams were triggered when a series of dams(complete blockage and partial blockage) were distributed along the ***,not all of these domino failures led to enlarg.d.debris *** modes of dam failures have significant impacts on the enlargement of debris ***,further research is necessary to understand the mechanisms of domino failures of landslide dams and their effects on the enlargement of debris flows.

关键词： debris flow Landslide dams domino failures Enlargement of debris flow Mean velocity

Polyethylene glycol fusion repair of severed sciatic nerves accelerates recovery of nociceptive sensory perceptions in male and female rats of different strains

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Neural Regeneration Research 2025年第9期20卷 2667-2681页

作者： Liwen zhou Karthik Venkudusamy Emily A.Hibbard Yessenia Montoya Alexa Olivarez Cathy Z.Yang Adelaide Leung Varun gokhale guhan Periyasamy Zeal Pathak dale R.Sengelaub george d.Bittner department of Neuroscience University of TexasAustinTXUSA Program in Neuroscience Indiana UniversityBloomingtonINUSA department of Molecular Biosciences University of TexasAustinTXUSA

Successful polyethylene glycol fusion(PEg-fusion)of severed axons following peripheral nerve injuries for PEg-fused axons has been reported to:(1)rapidly restore electrophysiological continuity;(2)prevent distal Wallerian degeneration and maintain their myelin sheaths;(3)promote primarily motor,voluntary behavioral recoveries as assessed by the Sciatic Functional Index;and,(4)rapidly produce correct and incorrect connections in many possible combinations that produce rapid and extensive recovery of functional peripheral nervous system/central nervous system connections and reflex(e.g.,toe twitch)or voluntary *** preceding companion paper describes sensory terminal field reo rganization following PEg-fusion repair of sciatic nerve transections or ablations;howeve r,sensory behavioral recovery has not been explicitly explored following PEg-fusion *** the current study,we confirmed the success of PEg-fusion surgeries according to criteria(1-3)above and more extensively investigated whether PEg-fusion enhanced mechanical nociceptive recovery following sciatic transection in male and female outbred Sprague-dawley and inbred Lewis *** nociceptive responses were assessed by measuring withdrawal thresholds using von Frey filaments on the dorsal and midplantar regions of the *** von Frey filament tests were a more reliable method than plantar von Frey filament tests to assess mechanical nociceptive sensitivity following sciatic nerve *** withdrawal thresholds of the sciatic-mediated lateral dorsal region differed significantly across strain but not *** thresholds did not change significantly from baseline in chronic Unoperated and Sham-operated *** sciatic transection,all rats exhibited severe hyposensitivity to stimuli at the lateral dorsal region of the hindpaw ipsilateral to the ***,PEg-fused rats exhibited significantly earlier return to baseline withdrawal thresholds than Negative

关键词： autophagia axotomy collateral sprouting neuropathic pain peripheral nerve repair polyethylene glycol fusion(PEg-fusion) saphenous nerve sensory neurons sex and strain Wallerian degeneration

Compression characteristics of saturated re-compacted glacial tills in Tianmo gully of Tibet, China

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Journal of Mountain Science 2019年第7期16卷 1661-1674页

作者： CHEN Lei-lei zhou gordon g.d.MU Qing-yi CUI Kahlil Fredrick SONg.d.ng-ri Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China University of Chinese Academy of Sciences Beijing 100049China department of Civil Engineering Xi'an Jiaotong UniversityXi'an 710049China

glacial tills are highly compressible soils composed of loosely cemented sandy silt *** role,for instance,as initial filler materials in geo-technical projects along temperate glacier regions warrant a systematic evaluation of their compressive *** such,we carry out a series of onedimensional compression tests on re-compacted glacial till samples obtained from Tianmo gully,Tibet,with the aims of evaluating their compressive behavior under controlled initial stress *** yield stress was determined from the void ratio versus consolidation pressure(e-log)*** compression and swelling behaviors were observed during the primary and secondary compressions of the consolidation *** the compression curves,a correlation can be found between the consolidation stress and the void *** addition,we find that the compression curves of glacial tills collapse into a single curve when normalized by the compression *** experimental results in this study provide a basic understanding of the compression characteristics of the glacial tills in Tibet,China.

关键词： glacial till Compression characteristics One-dimensional consolidation tests Consolidation stress Compression curve