检索结果-南通市图书馆

Two-flow model for piping erosion based on liquid-solid coupling

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2013年第8期20卷 2299-2306页

作者： LIANG Yue WANG Jun-jie liu ming-wei National Engineering Research Center for Inland Waterway Regulation (Chongqing Jiaotong University) Chongqing 400074 China Key Laboratory of Hydraulic & Waterway Engineering of the Ministry of Education (Chongqing Jiaotong University) Chongqing 400074 China

Previous studies have indicated that piping erosion greatly threatens the safe operation of various hydraulic structures. However, few mathematical models are available to perfectly describe the erosion process due to the complexity of piping. The focus of the present work is to propose a new fluid solid coupling model to eliminate the shortcomings of existing work. A 'pseudo-liquid' assumption is suggested to simulate the particle movement in the erosion process. Then, based on the mass and momentum conservations of the moving particles and flowing water, a new two-flow model is established by using the continuity equations and motion equations. In the model, the erosion rate of soil is determined with a particle erosion law derived from tests results of STERPI. And ERGUN's empirical equation is used to determine the interaction forces between the liquid and the solid. A numerical approach is proposed to solve the model with the finite volume method and SIMPLE algorithm. The new model is validated with the tests results of STERPI. And the soil erosion principles in piping are also explored.

关键词： piping erosion two-flow model liquid-solid interaction erosion rate drag force

Controls on the regional distribution of landslide dams and implications for fluvial landform evolution in Bhutan and its surrounding area

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2023年第8期20卷 2107-2132页

作者： ZHANG Qi-yuan HU Kai-heng liu Shuang liu wei-ming Institute of Mountain Hazards and Environment Chinese Academy of Sciences(CAS)Chengdu 610041China University of Chinese Academy of Sciences Beijing 100149China China-Pakistan Joint Research Center on Earth Sciences Islamabad 30001Pakist

The regional distribution of landslide dams can provide valuable insights into the interactions among various factors,including lithology,topography,climate,and fluvial landforms in tectonically active *** rivers are frequently impacted by large-scale landslide damming,which profoundly influence fluvial *** this study,we identified 1652 landslide dams in four major rivers of Bhutan and its surrounding area by remote sensing ***,approximately 71%of these landslide dams are found in regions composed of quartzite or ***-related tectonic activity plays a significant role in governing the distribution of these landslide dams,as approximately 83%of the mapped landslide dams are found within a 10 km radius of the nearest *** majority of the identified landslide dams are situated in areas with relatively modest local relief,ranging from 227 m to 327 *** dams tend to cluster in the tributaries,and the stream power of almost 95%of them is typically below 1×10^(6) kg m^(2) s^(-3).Our data,combining the erosion rate and kernel density map of the landslide dams,reveals that regions with high erosion rates do not consistently align with the major high-density distribution of landslide *** is shown that the distribution of landslide dams is strongly influenced by the valley *** comparison to U-shaped valleys,V-shaped valleys exhibit a higher density of landslide ***,we also find a positive correlation between the landslide-dam distribution density and the erosion rate only in relatively arid regions with mean annual rainfall less than 500 ***,the length of the upstream reach protected by the knickpoint associated with both lithology and landslide damming is about three times longer than that protected by the knickpoint associated only with landslide damming.

关键词： Bhutan Himalayas Landslide dams Erosion rate Geomorphological impacts Landscape evolution

Effect of Heat Input on Microstructure and Toughness of Coarse Grain Heat Affected Zone in Nb Microalloyed HSLA Steels

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2009年第5期16卷 73-80页

作者： ZHANG Ying-qiao ZHANG Han-qian LI Jin-fu liu wei-ming Department of Materials Science and Engineering Shanghai Jiao Tong University Shanghai 200030 China Research Institute for Advanced Structural Steel Research and Development Center Baoshan Iron and Steel Limited Company Shanghai 201900 China

The influence of Nb on microstructure, mechanical property and the transformation kinetics of the coarse grain heat affected zone （CGHAZ） in HSLA steels for different heat inputs, has been investigated. When welded at higher heat inputs （100-60 kJ/cm）, impact toughness values of the steel without Nb are much higher than those of the steel with Nb, and the lowest span is 153 J at 60 kJ/cm. But only a little higher values are observed at lower heat inputs （40-30 kJ/cm）, and the highest span is 68 J at 30 kJ/cm. Dilatation studies indicate that continuous cooling transformation starting temperatures （Ts） of CGHAZ for the steel with Nb are approximately 15-30℃ which are lower than those of the steel without Nb at all heat inputs. For higher heat inputs, Nb in solid solution suppresses ferrite transformation and promotes the formation of granular bainite which has detrimental effect on impact toughness. For lower heat inputs higher Charpy impact energy values in the steel with Nb are associated with the formation of low carbon self-tempered martensite.

关键词： HSLA steel coarse grain heat affected zone heat input Niobium impact toughness

Dynamic behaviour of weathered red mudstone in Sichuan(China)under triaxial cyclic loading

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2018年第8期15卷 1789-1806页

作者： ZHANG Chong-lei JIANG Guan-lu SU Li-jun liu wei-ming Key Laboratory of Mountain Hazards and Earth Surface Processes Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China Ministry of Education Key Laboratory of High-speed Railway EngineeringSchool of Civil EngineeringSouthwest Jiaotong UniversityChengdu 610031China. CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101China University of Chinese Academy of Sciences Beijing 100049China

The construction of a high-speed railway(HSR) in Southwest China is being hindered by a severe shortage of high-quality subgrade materials. However, red mudstone is widely distributed in the Sichuan Basin of China. The ability to use weathered red mudstone(WRM) to fill subgrade beds by controlling its critical stress and cumulative strain would enable substantial savings in project investments and mitigate damage to the ecological environment. To better understand the dynamic behaviour of WRM, both monotonic and cyclic triaxial tests were performed. The evolution of the cumulative strain vs. increased loading cycles was measured. The influences of confining pressure and loading cycles on the dynamic modulus, damping ratio, critical cyclic stress ratio(CSR), and dynamic stress level(DSL) were investigated. The relationship between the CSR and loading cycles under different failure strain criteria(0.1%-1.0%) was analysed. The prediction model of cumulative strain was also evaluated. The results indicated that the shear strength of WRM sufficiently meets the static strength requirements of subgrade. The critical dynamic stress of WRM can thus satisfy the dynamic stress-bearing requirement of the HSR subgrade. The critical CSR decreases and displays a power function with increasing confining pressure. As the confining pressure increases, the DSL remains relatively stable, ranging between 0.153 and 0.163. Furthermore, the relationship between the dynamic strength and loading cycles required to cause failure was established. Finally, a newly developed model for determining cumulative strain was established. A prediction exercise showed that the model is in good agreement with the experimental data.

关键词： Cyclic triaxial tests Cyclic stress ratio Red mudstone Critical dynamic stress Cumulative strain Railway subgrade

Chiral Separation of Spiro-compounds and Determination Configuration

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2008年第4期24卷 441-444页

作者： LIANG Ya GUO Jing-jing liu Xiu-ming wei Rong-bao School of Chemistry ＆ Chemical Engineering Tianjin University of Technology Tianjin 300191 P.R. China

Chiral spirocyclic compounds have attracted the attention of scholars and scientists owing to their potential applications in the pharmaceutical industry as either active pharmaceutical ingredients, catalysts in synthesizing active enantiomers, or as surface modifiers on silica particles to resolve entantiomers. In this study, five spiro compounds of 3,9-diphenyl-2,4,8,10-tetraoxaspiro[5.5]-undecane（1）, 3,9-（4-methoxyphenyl）-2,4,8,10-tetraoxaspiro [5.5] -undecane（2）, 3,9-（4-methylphenyl）-2,4,8,10-tetraoxaspiro [5.5] -undecane（3）, 4,4＇-（2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl）dibenzoic acid（4） and 3,9-di（4-formyl-phenyl）-2,4,8,10-tetraoxa-spiro[5.5]-undecane（5） were synthesized by grinding pentaerythritol with benzaldehyde, 4-methoxybenzaldehyde, 4-methylbenzaldehyde, 4-carboxybenzaldehyde or terephthalaldehyde monoacetal in the presence of InI3r3 under solvent-free conditions. A normal phase HPLC method was successfully developed to resolve entantiomers of compounds 1--5 on a chiral column. Specific optical rotation of R or S entantiomers（1） was determined and the corresponding configurations were proposed based on Lowe＇s rule.

关键词： Chiral separation Spiro-compounds Optical rotation

Geomorphic effect of debris-flow sediments on the Min River,Wenchuan Earthquake region,western China

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2021年第9期18卷 2427-2440页

作者： HU Xu-dong ZHOU Li-qin liu wei-ming WANG Hao CUI Lei College of Civil Engineering&Architecture China Three Gorges UniversityYichang 443002China Key Laboratory of Mountain Hazards and Earth Surface Processes Chinese Academy of SciencesChengdu 610041China Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China University of Chinese Academy of Sciences Beijing 100049China China Renewable Energy Engineering Institute Beijing 100049China

Coseismic landslides and subsequent mobilization of sediment greatly aggravated the landscape evolution and river sedimentation after the Wenchuan *** debris-flow alluvial fan and river morphological index was combined to describe quantitatively the effects of debris-flow sediment on the river characteristics in Longmen *** section of the Min River from the urban area of the Wenchuan county to the epicenter,the Yingxiu town in this county,was selected as the study *** identified 27 river-blocking debrisflows(5 partial-,7 semi-,7 over semi-,and 5 fullyblocking degrees)in the study area via remote sensing interpretation and field *** on this,the response of river longitudinal profile and curvature to debris-flow sediment was qualitatively and quantitatively *** results show that the channel gradient has decreased due to debris-flow aggradation,while two marked peaks in the river steepness index(ksn,represents the relative steepness degree of the channel)changed from 585 m0.9 to 732 m0.9 in zone 1,from 362 m0.9 to 513 m0.9 in zone ***,the main channel has undergone substantial lateral migration with channel width decreased and river curvature *** temporal and spatial variation between river morphological characteristics and debris-flow sediments in short-term provides insights into the internal dynamic role of mass wasting processes in river morphology,which could be served as useful information for natural hazards management to prevent the river from being blocked by episodically debris flows after the earthquake.

关键词： Debris-flow sediment Longitudinal profile River curvature Min River Wenchuan earthquake

Characteristics,Causes and Mitigation of Catastrophic Debris Flow Hazard on 21 July 2011 at the Longda Watershed of Songpan County,China

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2013年第2期10卷 261-272页

作者： GE Yong-gang CUI Peng GUO Xiao-jun SONG Guo-hu liu wei-ming Key Laboratory of Mountain Hazards and Earth Surface Processes Chinese Academy of Sciences Institute of Mountain Hazards and Environment Chinese Academy of Sciences University of Chinese Academy of Sciences

Debris flow is a common natural hazard in the mountain areas of Western China due to favorable natural conditions, and also exacerbated by mountainous exploitation activities. This paper concentrated on the characteristics, causes and mitigation of a catastrophic mine debris flow hazard at Longda Watershed in Songpan County, Sichuan Province, on 21 July 2011. This debris flow deposited in the front of the No.1 dam, silted the drainage channel for flood and then rushed into tailing sediment reservoir in the main channel and made the No.2 dam breached. The outburst debris flow blocked Fu River, formed dammed lake and generated outburst flood, which delivered heavy metals into the lower reaches of Fu River, polluted the drink water source of the population of over 1 million. The debris flow was characterized with a density of 1.87～2.15 t/m3 and a clay content of less than 1.63%. The peak velocity and flux at Longda Gully was over l0.0～10.9 m/s and 429.o～446.o m3/s, respectively, and the flux was about 700 m3/s in main channel, equaling to the flux of the probability of 1%. About 33o,ooorn3 solid materials was transported by debris flow and deposited in the drainage tunnel （120,000～130,000 m3）, the front of No.1 dam （100,000 m3） and the mouth of the watershed （l00,000～110,000 m3）, respectively. When the peak flux and magnitude of debris flow was more than 462 m3/s and 7,423 m3, respectively, it would block Fu River and produce a hazard chain which was composed of debris flow, dammed lake and outburst flood. Furthermore, the 21 July large-scale debris flow was triggered by rainstorm with an intensity of 21.2 mm/0.5 h and the solid materials of debris flow were provided by landslides, slope deposits, mining wastes and tailing sediments. The property losses were mainly originated from the silting of the drainage tunnel for flash flood but not for debris flow and the irrational location of tailing sediment reservoir. Therefore, the mitigation measures for mine debris flows

关键词： Debris Flow Characteristics Causes Mitigation Longda Watershed

Effect of dry density on the liquefaction behaviour of Quaternary silt

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2018年第7期15卷 1597-1614页

作者： ZHANG Chong-lei JIANG Guan-lu SU Li-jun liu wei-ming ZHOU Gong-dan Key Laboratory of Mountain Hazards and Earth Surface Processes Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences Chengdu 610043 China Ministry of Education Key Laboratory of High-speed Railway Engineering School of Civil Engineering Southwest Jiaotong University Chengdu 610031 China CAS Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101 China University of Chinese Academy of Sciences Beijing 100049 China

Quaternary silt is widely distributed in China and easily liquefies during earthquakes. To identify the influence of the dry density on the liquefaction behaviour of Quaternary silt, 40 cyclic triaxial liquefaction tests were performed on loose silt(dry density rd=1.460 g/cm^3) and dense silt(rd=1.586 g/cm^3) under different cyclic stress ratios(CSRs) to obtain liquefaction assessment criteria, determine the liquefaction resistance, improve the excess pore water pressure(EPWP) growth model and clarify the relationship between the shear modulus and damping ratio. The results indicate that the initial liquefaction assessment criteria for the loose and dense silts are a double-amplitude axial strain of 5% and an EPWP ratio of 1. The increase in the anti-liquefaction ability for the dense silt is more significant under lower confining pressures. The CSR of loose silt falls well within the results of the sandy silt and Fraser River silt, and the dense silt exhibits a higher liquefaction resistance than the sand-silt mixture. The relationships between the CSR and loading cycles were obtained at a failure strain of 1%. The EPWP development in the dense and loose silts complies with the "fast-stable" and "fast-gentle-sharp" growth modes, respectively. The power function model can effectively describe the EPWP growth characteristics of the dense silt. Finally, based on the liquefaction behaviour of silt, a suggestion for reinforcing silt slopes or foundations is proposed.

关键词： Liquefaction Quaternary silt Dry density Earthquake magnitude Liquefaction assessment Cyclic stress ratio

A review of surface damage/microstructures and their effects on hydrogen/helium retention in tungsten

在线全文

学校读者我要写书评

暂无评论

Tungsten 2020年第1期2卷 34-71页

作者： Yong‑Gang Li Qi‑Rong Zheng liu‑ming wei Chuan‑Guo Zhang Zhi Zeng Key Laboratory of Materials Physics Institute of Solid State PhysicsChinese Academy of SciencesHefei 230031China Science Island Branch of Graduate School University of Science and Technology of ChinaHefei 230026China

The change in surface damage/microstructures and its effects on the hydrogen(H)isotope/helium(He)dynamic behavior are the key factors for investigating issues of tungsten(W)-based plasma-facing materials(PFMs)in fusion such as surface erosion,H/He retention and tritium(T)*** surface damage/microstructures are introduced in W by high-temperature plasma irradiation and new material design,typically including pre-damage and multi-ion co-deposition induced structures,solute elements and related composites,native defects like dislocations and interfaces,and *** experimental and theoretical researches were performed on H isotope/He retention in complex W-based materials in the past *** this review,we aim to provide an overview of typical surface damage/microstructures and their effects on H/He retention in W,both in the experiment and multiscale *** distribution/state,dynamics evolution,and interaction with defects/microstructures of H/He are generally summarized at different ***,the current difficulties,challenges and future directions are also discussed about H/He retention in complex W-based PFMs.

关键词： Surface damage/microstructures Hydrogen/helium retention Tungsten Plasma-facing materials