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

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 enlarged 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

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An experimental study:Integration device of Fiber Bragg grating and reinforced concrete beam for measuring debris flow impact force

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Journal of Mountain Science 2017年第8期14卷 1526-1536页

作者： ZHANG Shao-jie CHEN Jiang Key laboratory of Mountain Hazards and earth surface process Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences College of Architecture & environment Sichuan University

The impact effect of boulder within debris flow is the key factor contributing to peak impact as well as to the failure of debris flow control work. So accurate measuring and calculating the impact force of debris flow can ensure the engineering design strength. However, limited to the existing laboratory conditions and piezoelectric sensor performance, it is impossible, based on the conventional measurements, to devise a computing method for expressing a reliable boulder impact force. This paper has therefore designed a new measurement device according to the method of integrating Fiber Bragg grating(FBG) and reinforced concrete composite beam(RCB) for measuring the impact force of debris flows, i.e. mounting FBG on the axially stressed steel bar in the composite beam at regular intervals to monitor the steel strain. RCB plays the role of contacting debris flow and protecting FBG sensors. Taking this new device as the experimental object, drop testing is designed for simulating and reflecting the boulder impact force. In a series of impacting tests, the relationship between the peak dynamic strain value of the steel bar and the impact force is analyzed, and based on which, an inversion model that uses the steel bar strain as the independent variable is established for calculating the boulder impact *** experimental results show that this new inversion model can determine the impact force value and its acting position with a system error of 18.1%, which can provide an experimental foundation for measuring the impact force of boulders within the debris flow by the new FBG-based device.

关键词： Fiber Bragg grating Measurementdevice Debris flow Boulder Impact force

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Sand dunes as potential sources of dust in northern China

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Science China earth Sciences 2016年第4期59卷 760-769页

作者： Mark R SWEENEY LU HuaYu CUI MengChun Joseph A MASON FENG Han XU ZhiWei Department of earth Sciences University of South Dakota laboratory of earth surface process and environment School of Geographic and Oceanographic Sciences Nanjing University Department of Geography University of Wisconsin-Madison

While saltation bombardment of sand grains on a fine substrate can produce considerable dust, the well-sorted nature of sand dunes tends to preclude them from consideration as major dust sources. Recent research, however, has revealed that sand dunes can, in some cases, be large sources of dust. We used the PI-SWERL(Portable In-Situ Wind Erosion laboratory) to measure in the field the potential of sand dunes and other desert landforms to emit particulate matter <10 μm(PM-10) dust in the Tengger, Ulan Buh, and Mu Us deserts of northern China. Combined with high resolution particle size measurements of the dune sand, an assessment of sand dunes as a dust source can be made. Large active transverse dunes tend to contain little to no stored PM-10, yet they produce a low dust flux. Coppice dunes stabilized by vegetation contain appreciable PM-10 and have very high dust emission potential. There is a positive correlation between the amount of PM-10 stored in a dune and its potential dust flux. Saltation liberates loose fines stored in dunes, making them very efficient dust emitters compared to landforms such as dry lake beds and washes where dust particles are unavailable for aeolian transport due to protective crusts or sediment cohesion. In cases where large dunes do not store PM-10 yet emit dust when active, two hypotheses can be considered:(1) iron-oxide grain coatings are removed during saltation, creating dust, and(2) sand grains collide during saltation, abrading grains to create dust. Observations reveal that iron oxide coatings are present on some dune sands. PI-SWERL data suggests that low dust fluxes from dunes containing no stored dust may represent an estimate for the amount of PM-10 dust produced by removal of iron oxide coatings. These results are similar to results from dunes in the United States. In addition, PI-SWERL results suggest that dust-bearing coppice dunes, which cover vast areas of China's sandy deserts, may become major sources of dust in the f

关键词： Coppice dunes Transverse dunes Dust PI-SWERL Desert

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A Model of Debris Flow Forecast Based on the Water-Soil Coupling Mechanism

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Journal of earth Science 2014年第4期25卷 757-763页

作者： Shaojie Zhang Hongjuan Yang Fangqiang Wei Yuhong Jiang Dunlong Liu Key laboratory of Mountain Hazards and earth surface process Chinese Academy of Sciences Institute of Mountain Hazards and environment Chinese Academy of Sciences

Debris flow forecast is an important means of disaster mitigation. However, the accuracy of the statistics-based debris flow forecast is unsatisfied while the mechanism-based forecast is unavailable at the watershed scale because most of existing researches on the initiation mechanism of debris flow took a single slope as the main object. In order to solve this problem, this paper developed a model of debris flow forecast based on the water-soil coupling mechanism at the watershed scale. In this model, the runoff and the instable soil caused by the rainfall in a watershed is estimated by the distrib- uted hydrological model （GBHM） and an instable identification model of the unsaturated soil. Because the debris flow is a special fluid composed of soil and water and has a bigger density, the density esti- mated by the runoff and instable soil mass in a watershed under the action of a rainfall is employed as a key factor to identify the formation probability of debris flow in the forecast model. The Jiangjia Gulley, a typical debris flow valley with a several debris flow events each year, is selected as a case study watershed to test this forecast model of debris flow. According the observation data of Dongchuan Debris Flow Observation and Research Station, CAS located in Jiangjia Gulley, there were 4 debris flow events in 2006. The test results show that the accuracy of the model is satisfied.

关键词： debris flow forecast watershed scale soil-water coupling distributed hydrological model limit equilibrium analysis Jiangjia Gulley.

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Mean Velocity Estimation of Viscous Debris Flows

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Journal of earth Science 2014年第4期25卷 771-778页

作者： Hongjuan Yang Fangqiang Wei Kaiheng Hu Key laboratory of Mountain Hazards and earth surface process Chinese Academy of Sciences Institute of Mountain Hazards and environment Chinese Academy of Sciences

The mean velocity estimation of debris flows, especially viscous debris flows, is an important part in the debris flow dynamics research and in the design of control structures. In this study, theoretical equations for computing debris flow velocity with the one-phase flow assumption were reviewed and used to analyze field data of viscous debris flows. Results show that the viscous debris flow is diffficult to be classified as a Newtonian laminar flow, a Newtonian turbulent flow, a Bingham fluid, or a dilatant fluid in the strict sense. However, we can establish empirical formulas to compute its mean velocity following equations for Newtonian turbulent flows, because most viscous debris flows are tur- bulent. Factors that potentially influence debris flow velocity were chosen according to two-phase flow theories. Through correlation analysis and data fitting, two empirical formulas were proposed. In the first one, velocity is expressed as a function of clay content, flow depth and channel slope. In the second one, a coefficient representing the grain size nonuniformity is used instead of clay content. Both formulas can give reasonable estimate of the mean velocity of the viscous debris flow.

关键词： debris flow velocity one-phase flow two-phase flow viscous.

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Comparison of Rheometric Devices for Measuring the Rheological Parameters of Debris Flow Slurry

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Journal of Mountain Science 2015年第5期12卷 1125-1134页

作者： YANG Hong-juan WEI Fang-qiang HU Kai-heng ZHOU Gong-dan LYU Juan Key laboratory of Mountain Hazards and earth surface process Chinese Academy of Sciences Institute of Mountain Hazards and environment Chinese Academy of Sciences

Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton Paar Physica MCR301 rheometer, including the concentric cylinder system,the parallel-plate system, the vane geometry, and the ball measuring system. All systems were smoothwalled. Flow curves were plotted and yield stress was determined using the Herschel-Bulkley model,showing differences among the different *** curves from the concentric cylinder and parallelplate systems involved two distinct regions, the low shear and the high shear regions. Yield stresses determined by data fitting in the low shear region were significantly lower than the values from the inclined channel test which is a practical method for determining yield stress. Flow curves in the high shear region are close to those from the vane geometry and the ball measuring system. The fitted values of yield stress are comparable to the values from the inclined channel test. The differences are caused by wall-slip effects in the low shear *** geometry can capture the stress overshoot phenomenon caused by the destruction of slurry structure, whereas end effects should be considered in the determination of yield stress. The ball measuring system can give reasonable results, and it is applicable for rheological testing of debris flow slurries.

关键词： Debris flow Slurry Rheometer Concentric cylinder system Parallel plate system Vane Ball measuring system

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Determination of the suspension competence of debris flows based on particle size analysis

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International Journal of Sediment Research 2014年第1期29卷 73-81页

作者： Hong-juan YANG Fang-qiang WEI Kai-heng HU Chuan-chang WANG Key laboratory of Mountain Hazards and earth surface process Chinese Academy of Sciences Institute of Mountain Hazards and environment Chinese Academy of Sciences

The determination of the critical particle size between solid and fluid phases,i.e.,the suspension competence,is fundamental for debris flow.A method for determining suspension competence based on particle size analysis is presented in this *** competence of static experimental water-debris mixtures prepared with the sediment of Jiangjia Gully is-0.025 mm if the bulk density is less than 1,800 kg m;and it increases with bulk density of more concentrated *** competence of natural debris flows in Jiangjia Gully increases exponentially with the bulk *** two data sets are compared in order to understand the suspension *** is concluded that turbulence may play a leading role in particle suspension in non-viscous and sub-viscous debris flows,while in viscous debris flows both matrix strength and excess pore water pressure play important roles.

关键词： Debris flow Suspension competence Particle size analysis Critical particle size Particle suspension mechanism

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A Regional-Scale Method of Forecasting Debris Flow Events Based on Water-Soil Coupling Mechanism

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Journal of Mountain Science 2014年第6期11卷 1531-1542页

作者： ZHANG Shao-jie WEI Fang-qiang LIU Dun-long YANG Hong-juan JIANG Yu-hong Key laboratory of Mountain Hazards and earth surface process Chinese Academy of Sciences Institute of Mountain Hazards and environment Chinese Academy of Sciences

A debris flow forecast model based on a water-soil coupling mechanism that takes the debrisflow watershed as a basic forecast unit was established here for the prediction of disasters at the watershed *** was achieved through advances in our understanding of the formation mechanism of debris *** expand the applicable spatial scale of this forecasting model,a method of identifying potential debris flow watersheds was used to locate areas vulnerable to debris flow within a forecast *** these watersheds as forecasting units and a prediction method based on the water-soil coupling mechanism,a new forecasting method of debris flow at the regional scale was *** order to test the prediction ability of this new forecasting method,the Sichuan province,China was selected as a study zone and the large-scale debris flow disasters attributable to heavy rainfall in this region on July 9,2013 were taken as the study *** to debris flow disaster data on July 9,2013 which were provided by the geo-environmental monitoring station of Sichuan province,there were 252 watersheds in which debris flow events actually *** current model predicted that 265 watersheds were likely to experience a debris flow *** these,43 towns including 204 debrisflow watersheds were successfully forecasted and 24 towns including 48 watersheds *** false prediction rate and failure prediction rate of thisforecast model were 23% and 19%,*** results show that this method is more accurate and more applicable than traditional methods.

关键词： Debris flow Forecasting Water-soil coupling mechanism Watershed

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Influence of inflow discharge and bed erodibility on outburst flood of landslide dam

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Journal of Mountain Science 2019年第4期16卷 778-792页

作者： ZHOU Ming-jun ZHOU Gordon G.D. CUI Kahlil Fredrick E. SONG Dong-ri LU Xue-qiang Key laboratory of Mountain Hazards and earth surface process/Institute of Mountain Hazards and environment Chinese Academy of Sciences University of Chinese Academy of Sciences

Accurate prediction of the hydrographs of outburst floods induced by landslide dam overtopping failure is necessary for hazard prevention and mitigation. In this study, flume model tests on the breaching of landslide dams were conducted. Unconsolidated soil materials with wide grain size distributions were used to construct the dam. The effects of different upstream inflow discharges and downstream bed soil erosion on the outburst peak discharge were investigated. Experimental results reveal that the whole hydrodynamic process of landslide dam breaching can be divided into three stages as defined by clear inflection points and peak discharges. The larger the inflow discharge, the shorter the time it takes to reach the peak discharge, and the larger the outburst flood peak discharge. The scale of the outburst floods was found to be amplified by the presence of an erodible bed located downstream of the landslide dam. This amplification decreases with the increase of upstream inflow. In addition, the results show that the existence of an erodible bed increases the density of the outburst flow, increasing its probability of transforming from a sediment flow to a debris flow.

关键词： Landslide dam Inflow discharge Erodible bed Outburst flood

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Mechanism of Downcutting Erosion of Debris Flow over a Movable Bed

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Journal of Mountain Science 2015年第1期12卷 243-250页

作者： Pan Hua-li Huang Jiang-cheng Ou Guo-qiang Key laboratory of Mountain Hazards and earth surface process Institute of Mountain Hazards and Environment CAS Asian International Rivers Center Yunnan University

The phenomenon of debris flow is intermediate between mass movement and solid transport. Flows can be sudden, severe and destructive. Understanding debris flow erosion processes is the key to providing geomorphic explanations, but progress has been limited because the physical-mechanical properties, movement laws and erosion characteristics are different from those of sediment-laden flow. Using infinite slope theory, this research examines the process and mechanism of downcutting erosion over a moveable bed in a viscous debris flow gully. It focuses specifically on the scour depth and the critical slope for viscous debris flow,and formulas for both calculations are *** scour depth and the critical conditions of downcutting erosion are related to debris flow properties(sand volume concentration and flow depth) and gully properties(longitudinal slope,viscous and internal friction angle of gully materials,and coefficient of kinetic friction). In addition, a series of flume experiments was carried out to characterize the scouring process of debris flows with different properties. The calculated values agreed well with the experimental data. These theoretical formulas are reasonable, and using infinite slope theory to analyze down cutting erosion from viscous debris flow is feasible.

关键词： Debris flow Down cutting erosion Infinite slope theory Critical conditions Flumeexperiments

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