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Local Scour and the Laws of Scour Pit's Shape Downstream of Debris Flow Sabo Dam

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Journal of Mountain Science 2013年第6期10卷 1063-1073页

作者： pan hua-li YANG Shun OU Guo-qiang huaNG Jiang-cheng Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences Graduate University of Chinese Academy of Sciences Asian International Rivers Center Yunnan University Yunnan Key Laboratory for International Rivers and Transboundary Ecology Security

The erosion shape and the law of development of debris flow sabo dam downstream is a weak part in the study on debris flow erosion. The shape and development of scour pit have an important effect on the stability and safety of debris flow sabo dam, which determines the foundational depth of the dam and the design of protective measures downstream. Study on the scouring law of sabo dam downstream can evaluate the erosion range and reasonably arrange auxiliary protective engineering. Therefore, a series of flume experiments are carried out including different debris flow characteristics （density is varying from 1.5 t/m3 to 2.1 t/m~） and different gully longitudinal slopes. The result shows that the scour pit appears as an oval shape in a plane and deep in the middle while superficial at the ends in the longitudinal section, the position of the maximum depth point moves towards downstream with an increase of flume slope angle. The maximum depth of scour pit is mainly affected by the longitudinal slope of gully, density of debris flow, and the characteristics of gully composition （particle size and the viscosity of soil）. The result also indicates that the viscosity of soil will weaken the erosion extent. The interior slopes of scour pit are different between the upstream and the downstream, and the downstream slope is smaller than the upper one. For the viscous and non-viscous sands with the same distribution of gradation, the interior slope of non- viscous sand is smaller than the viscous *** to tbe regression analysis on the experimental data, the quantitative relationship between the interior slope of scour pit, slope of repose under water and the longitudinal slope of gully is established and it can be used to calculate the interior slope of scour pit. The results can provide the basis for the parameter design of the debris flow control engineering foundation.

关键词： Scour pit Debris flow Sabo dam Scouring law Interior slope Flume experiment

High-Speed Ring Shear Tests to Study the Motion and Acceleration Processes of the Yingong Landslide

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Journal of Mountain Science 2015年第6期12卷 1534-1541页

作者： HU Ming-jian pan hua-li Zhu Chang-qi Wang Fa-wu State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and Environment Chinese Academy of Sciences Research Center on Natural Disaster Reduction Shimane University

In this paper, the motion and acceleration process, as well as the mechanism of a high speed and long run landslide are investigated by adopting high speed ring shear test and taking the landslide occurred at Yigong River in Bomi, Tibet on April 9, 2000 as the background. According to the motion characteristics of high-speed and long distance motion landside, the mechanism is studied under different conditions such as shear speed, consolidated drained and consolidated undrained status. Results show that high speed shearing process hinders and delays the dissipation of pore pressure, and drives pore water migrating to shear zone slowly. Both of water content and fine particle content at shear zone are obviously higher than those in other layers; and soil liquefaction occurs at shear zone in the saturated consolidated undrained ring shear tests. The effective internal friction angle of the consolidated undrained soil is much lower than that of the consolidated drained soil under ring shearing. The results also indicate that the shearing speed affecting the strength of soil to some extent. The higher the ring shearing speed is, the lower the strength of soil is. This investigation provides a preliminary interpretation of the mechanism of the motion and acceleration process of the Yigong landslide, occurred in Tibet in 2000.

关键词： Yigong landslide Ring shear tests Shear zone liquefaction Strength

Debris Flow Formation Process and Critical Hydrodynamic Conditions in the Meizoseismal Area of the Wenchuan Earthquake

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Journal of Mountain Science 2015年第3期12卷 699-710页

作者： WANG Jun YU Yan pan hua-li QIAO Cheng OU Guo-qiang Key Laboratory of Mountain Hazards and Earth Surface Process Chinese Academy of Sciences Institute of Mountain Hazards and Environment Chinese Academy of Sciences University of Chinese Academy of Sciences

Abstract： The Wenchuan earthquake generated strong surface disturbances and triggered a large number of loose deposits, resulting in the disaster- prone environment with special watershed hydrological characteristics. This paper was to propose a debris flow formation process and explore the permeability characteristics and critical hydrodynamic conditions of the loose deposits triggered by the earthquake. The Guo Juanyan gully （31005＇27＂ N to 31005＇46＂ N, 103036＇58＂ E to 103037＇09＂ E） in Du Jiangyan City, located in the meizoseismal areas of the Wenchuan earthquake, was chosen as the study area and the disaster-prone environment was analyzed. The formation process of the debris flow was first proposed using a stability analysis, and then, the permeability characteristics of loose deposits were determined via in situ permeability experiments. Finally, the critical 1 h rainfall was simulated through a distributed hydrological model and verified by field observations. The formation process of debris flow could be divided into three stages based on the relationship between the hydrodynamic force and loose deposit resistance. The critical 1 h rainfall amounts under three antecedent moisture conditions （I-dry, Ⅱ-normal and Ⅲ-wet） were 52 mm/h, 43 mm/h and 34 mm/h, respectively. This study proposed a debris flow formation process in the meizoseismal areas of the Wenchuan earthquake based on the stability analysis and defined the rainfall threshold for debris flow early warning at the local level, which is significant for debris flow mitigation and risk management.

关键词： Wenchuan Earthquake Debris flow Disaster-prone environment Permeabilitycharacteristics Hydrodynamic condition

Landslides & Debris Flows Formation from Gravelly Soil Surface Erosion and Particle Losses in Jiangjia Ravine

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Journal of Mountain Science 2013年第6期10卷 987-995页

作者： HU Ming-jian pan hua-li WEI Hou-zhen WANG Ren A Ying State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and Environment Chinese Academy of Sciences

Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow.

关键词： Gravelly soils Erosion process Particlelosses Runoff sediment content JiangJia Ravine

Long runout mechanism of the Shenzhen 2015 landslide:insights from a two-phase flow viewpoint

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Journal of Mountain Science 2018年第10期15卷 2247-2265页

作者： QIAO Cheng OU Guo-qiang pan hua-li OUYANG Chao-jun JIA Yang Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China Key Laboratory of Mountain Surface Process and Hazards Chinese Academy of SciencesChengdu 610041China University of Chinese Academy of Sciences Beijing 100049China Anhui University of Science&Technology Huainan 232002China

A catastrophic landslide occurred at Hongao dumpsite in Guangming New District of Shenzhen, South China, on December 20, 2015. An estimated total volume of 2.73×106 m3 of construction spoils was mobilized during this event. The landslide traveled a long distance on a low-relief terrain. The affected area was approximately 1100 m in length and 630 m in width. This landslide made 33 buildings destroyed, 73 people died and 4 people lost. Due to the special dumping history and other factors, soil in this landfill is of high initial water content. To identify the major factors that attribute to the long runout character, a two-phase flow model of Iverson and George was used to simulate the dynamics of this landslide. The influence of initial hydraulic permeability, initial dilatancy, and earth pressure coefficient was examined through numerical simulations. We found that pore pressure has the most significant effect on the dynamic characteristics of Shenzhen landslides. Average pore pressure ratio ofthe whole basal surface was used to evaluate the degree of liquefaction for the sliding material. The evolution and influence factors of this ratio were analyzed based on the computational results. An exponential function was proposed to fit the evolution curve of the average pore pressure ratio, which can be used as a reasonable and simplified evaluation of the pore pressure. This fitting function can be utilized to improve the single-phase flow model.

关键词： Dynamics Landslide Long runout Pore pressure Two-phase

Denitrifying Bacteria in Paddy Soils of the Taihu Lake Basin,China

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Pedosphere 2004年第4期14卷 527-532页

作者： ZHANGhua-Yong liZhen-Gao panYing-hua liliang-Mo InstituteofSoilScience ChineseAcademyofSciencesNanjing210008（China）.

This study attempted to determine the characteristics of the communities, the ecological factors, and the denitrifying enzyme activity for denitrifying bacteria found in the paddy soils of the Taihu Lake Basin, China. Samples of the six main soil types of the basin were taken from paddy fields with different fertilities. The total numbers of bacteria and denitrifying bacteria in the high fertility soils were much more than those in low fertility soils, and the number of denitrifying bacteria accounted for 49% to 80% of the total number of bacteria. The O2 content was an important ecological factor that affected denitrification. Of test the strains isolated from the paddy soils in the Taihu Lake Basin, some (e.g., Pseudomonas spp.) grew well under low oxygen partial pressure, while others (e.g., Bacillus spp.) had no strict predilection with O2 content. Another critical ecological factor was the nitrogen concentration. Three selected denitrifying bacteria grew better in aculture medium with 135 instead of 276mg L^-1 nitrogen. At the same time 67% of the test strains were able to reduce NO3^- to NO2^- and 56% had N2O reductase.

关键词： denitrifying bacteria ecological characteristics enzyme activity paddysoils

Quantitative Trait Loci Associated with Pollen Fertility under High Temperature Stress at Flowering Stage in Rice (Oryza sativa)

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Rice science 2011年第3期18卷 204-209页

作者： Ying-hui XIAO Yi pan li-hua LUO hua-bing DENG Gui-lian ZHANG Wen-bang TANG li-yun CHEN Rice Research Institute Hunan Agricultural University Changsha 410128 China

High temperature stress (HTS), an increasingly important problem in rice production, significantly reduces rice yield by reducing pollen fertility and seed setting rate. Breeding rice varieties with tolerance to HTS at the flowering stage is therefore essential for maintaining rice production as the climate continues to become warm. In this study, two quantitative trait loci (QTLs) underlying tolerance to HTS were identified using recombinant inbred lines derived from a cross between an HTS-tolerant rice cultivar 996 and a sensitive cultivar 4628. Pollen fertility was used as a heat-tolerance indicator for the lines subjected to HTS at the flowering stage in field experiments. Two QTLs that affected pollen fertility, qPF4 and qPF6, were detected between RM5687 and RM471 on chromosome 4, and between RM190 and RM225 on chromosome 6, by using the composite interval mapping (CIM) analysis. The two QTLs explained 15.1% and 9.31% of the total phenotypic variation in pollen fertility, and increased the pollen fertility of the plants subjected to HTS by 7.15% and 5.25%, respectively. The positive additive effects of the two QTLs were derived from the 996 alleles. The two major QTLs identified would be useful for further fine mapping and cloning of these genes and for molecular marker-assistant breeding of heat-tolerant rice varieties.

关键词： rice quantitative trait locus pollen fertility high temperature stress

Study on Uncertainties of Seismicity Parameters b and ν_4 in Seismic Statistical Zones

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Earthquake Research in China 2007年第3期21卷 318-326页

作者： pan hua li Jinchen li Zhiguo Institute of Geophysics China Earthquake Administration Beijing 100081 China

For several seismic statistical zones in North China, the key factors causing uncertainties in the important seismicity parameters b and v4 and the features of their uncertainties are discussed in this paper. The magnitude of uncertainty is also analyzed. It can be seen that the key influencing factors are statistical period, methods of processing statistical samples, lower limit magnitude and the annual average occurrence ratio of large earthquakes. The variation ranges of b and v4 in the Tancheng-Lujiang zone are as high as 0.2 and 1. 4 respectively, which are similar to those in the Fenwei zone. They are much smaller however in the Hebei zone because of its sufficient statistical samples.

关键词： Seismic statistical zone Seismicity parameters b value v4 Uncertainty

Modeling and Simulation of Radial-Axial Large Ring Rolling

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Computer Aided Drafting,Design and Manufacturing 2007年第1期17卷 19-24页

作者： pan li-bo hua lin LAN Jian School of Materials Science and Engineering Wuhan University of Technology Wuhan 430074 China

Finite element model is constructed according to the principle and characteristics of radial-axial large ring rolling technology. Dynamic explicit finite element method is used to simulate the rolling process. An effective modeling method of guide roller is proposed. Simulation indicates that high quality ring product could be obtained when rational rotational speed of rollers and feed rate in the radial and axial rolling are assigned.

关键词： large ring radial-axial ring rolling finite element simulation