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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

Natural consolidation characteristics of viscous debris flow deposition

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Journal of Mountain Science 2016年第10期13卷 1723-1734页

作者： HE Song-Tang WANG Dao-Jie CHEN Shun ZHANG Shu-Juan CHANG Shi-Qiu Key Laboratory of Mountain Hazards and Earth Surface Processes Chinese Academy of SciencesChengdu 610041China Institute of Mountain Hazards and Environment Chinese Academy of Science&Ministry of Water ConservancyChengdu 510041China University of Chinese Academy of Sciences Beijing 100049China

Pore water pressure and water content are important indicators to both deposition and consolidation of debris flows, enabling a direct assessment of consolidation degree. This article gained a more comprehensive understanding about the entire consolidation process and focused on exploring pore water pressure and volumetric water content variations of the deposit body during natural consolidation under different conditions taking the viscous debris flow mass as a study subject and by flume experiments. The results indicate that, as the color of the debris changed from initial dark green to grayish-white color, the initial deposit thickness declined by 3% and 2.8% over a permeable and impermeable sand bed, respectively. A positive correlation was observed between pore water pressure and depth in the deposit for both scenarios, with deeper depths being related to greater pore water pressure. For the permeable environment, the average dissipation rate of pore water pressure measured at depths of 0.10 m and 0.05 m were 0.0172 Pa/d and 0.0144 Pa/d, respectively, showing a positivechanging trend with increasing depth. Under impermeable conditions, the average dissipation rates at different depths were similar, while the volumetric water content in the deposit had a positive correlation with depth. The reduction of water content in the deposit accelerated with depth under impermeable sand bed boundary conditions, but was not considerably correlated with depth under permeable sand bed boundary conditions. However, the amount of discharged water from the deposit was greater and consolidation occurred faster in permeable conditions. This indicates that the permeability of the boundary sand bed has a significant impact on the progress of consolidation. This research demonstrates that pore water and pressure dissipations are present during the entire viscous debris consolidation process. Contrasting with dilute flows, pore pressure dissipation in viscous flows cannot be complete

关键词： Viscous debris flow Natural consolidation Dissipation of pore water pressure Volumetric Water content flume experiment

Modeling of breaching parameters for debris flow dams

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Journal of Mountain Science 2023年第10期20卷 2835-2851页

作者： RUAN He-chun CHEN Hua-yong CHEN Xiao-qing ZHAO Wan-yu CHEN Jian-gang WANG Tao JIANG Yao Wang Xi-an Li Xiang-ning LI Xiao YU Yun-han Key Laboratory of Mountain Hazards and Surface Processes Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China University of Chinese Academy of Sciences Beijing 100000China

The debris flow dam is a common type of barrier dams,which shows significant differences from other types of barrier dam such as landslide dam,moraine dam in their formation processes,dam body shapes,and internal *** basic breaching parameters such as flood peak discharge are vital indicators of risk *** this study,we elucidated the failure process of the debris flow dam through the flume experiment,and built the calculation equation of the breaching parameters by selecting critical *** result shows that the overtopping failure process of the debris flow dam is capable of forming significantly retrogressive scarps,and the failure process experiences three stages,the formation of the retrogressive scarp,the erosion of the retrogressive scarp,and the decline of the retrogressive *** factors used for establishing the calculation equations for peak discharge(Qp),final width(Wb)of the breach,and duration(T)of the debris flow dam failure are dam height(h),reservoir capacity(V),the fine grain content(P0.075)of the soil,the nonuniformity coefficient(Cu)of the soil,and the upper limit grain size(D90)of the soil,*** the three equations,the correlation coefficients between Qp,Wb,T and the five factors were 0.86,0.70,0.63,*** equations still need to be modified and verified in actual cases.

关键词： Debris flow dams Overtopping failure Breaching g parameters Peak discharge flume experiment

Calculation of the ultimate depth of a scour pit after debris flow through drainage canal ribs

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Journal of Mountain Science 2016年第2期13卷 246-254页

作者： LIU Shu-liang YOU Yong ZHANG Guang-ze ZHAO Hai-xin SUN Hao Key Laboratory of Mountain Hazards and Earth Surface Process Chinese Academy of Sciences Chengdu 610041 China Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China University of Chinese Academy of Sciences Beijing 100049 China China Railway Eryuan Engineering Group co. LTD Chengdu 610031 China

Drainage canals are engineering structures widely used for debris flow *** passing through a drainage canal,debris flow usually scours the gully bed at the back of the rib sill of the drainage canal,which leads to failure of the rib ***,the scour depth at the back of the rib sill is an important design problem and it is related to the economic benefits of engineering and service *** explore the law of the depth of the scour pit after debris flow through drainage canal ribs,we first proposed a formula for the calculation of the maximum scour depth at the back of a rib sill based on energy *** then conducted a series of simulation experiments to test the proposed *** experimental results show that the scour depth,trench slope and the distance between ribs all increase with a decrease in debris flow *** then compared the results of experiments and formula *** the testing analysis,we found that the calculation results of the conductedformula correspond with the experimental results ***,taking Qipan Gully as an example,we designed the ultimate depth of a drainage canal for debris flow using the calculation formula.

关键词： Debris flow Drainage canal Scour depth Energy conservation method flume experiment

experimental study on blocking and self-cleaning behaviors of beam dam in debris flow hazard mitigation

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International Journal of Sediment Research 2018年第4期33卷 395-405页

作者： Hao Sun Yong You Jinfeng Liu 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

Blocking is one of the important features when a beam dam intercepts debris flow, while self-cleaning is another when managing suspended debris flow. Both features determine the debris flow control benefits of beam dam but the latter often is not considered in practical engineering design. In this paper, a series of specially designed flume experiments were done to simulate blocking and self-cleaning processes. The blocking ratio and deposition features were measured to contrast the blocking and self-cleaning performance before and after artificial self-cleaning. The experimental results reveal that the beam dam net opening, particle diameter of sediment, sediment concentration, and gradient of the channel are the main factors affecting blocking performance. A new criterion of blocking performance of beam dams that considers the interaction of multiple factors and can provide guidance to practical project design is proposed. For all three types of blocking, sediment deposited upstream of a beam dam can be effectively transported downstream by erosion from post-debris-flow floods, Self-cleaning performance is most efficient for temporary blocking, followed by partial-blocking, and total-blocking. The efficiency of selfcleaning largely depends on the change of the sediment deposit due to erosion. Finally, a discussion is given for the optimal design of an open-type check dam and the feasibility of synergistic effects of selfcleaning in combination with artificial cleaning. Some supporting artificial silt-cleaning should be implemented in practice. A beam dam will, thus, have more storage capacity with which to control the next debris flow event.

关键词： Debris flow Beam dam Critical blocking criterion Self-cleaning flume experiment

experimental Study of Pore Water Pressure and Bed Profile Change Under Regular Breaking Waves

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China Ocean Engineering 2012年第3期26卷 457-468页

作者：程永舟蒋昌波赵利平潘昀李青峰 School of Hydraulic Engineering Changsha University of Science&Technology Key Laboratory of Water&Sediment Science and Water Hazard Prevention Hunan Province

There lies a close relationship between the seabed destruction and the distribution of pore water pressure under the action of breaking wave. The experiments were carried out in a wave flume with a 1：30 sloping sandy seabed to study regular breaking wave induced pore water pressure. A wide range of measurements from the regular wave runs were reported, including time series of wave heights, pore pressures. The video records were analysed to measure the time development of the seabed form and the characteristics of the orbital motion of the sand in the wave breaking region. The pore water pressure in the breaker zone showed the time variation depending on the wave phases including wave breaking and bore propagation. The time-averaged pore water pressure was higher near the seabed surface. The peak values of pore water pressure increase significantly at the breaking point. The direction of pore water pressure difference forces in the breaker zone is of fundamental importance for a correct description of the sediment dynamics. The upwards- directed pressure differences may increase sand transport by reducing the effective weight of the sediment, thereby increasing the bed form evolution. The seabed configuration changed greatly at the wave breaking zone and a sand bar was generated remarkably. The amplitude of the pore water pressure changed with the seabed surface. The results are to improve the understanding of sand transport mechanisms and seabed responses due to breaking regular waves over a sloping sandy bed.

关键词： breaking wave pore water pressure sloping sandy seabed flume experiment

Scour around submarine pipes due to high-amplitude transient waves

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Water Science and Engineering 2020年第2期13卷 154-161页

作者： Hassan Vosoughi Hooman Hajikandi Department of Civil Engineering Central Tehran BranchIslamic Azad UniversityTehran ***Iran

Estimation of scour dimensions below submarine pipelines is a vital step in designing offshore *** events like tsunami waves produce strong erosive forces below the underwater pipes,apt to create scour holes,jeopardizing the safety of the *** the importance of this issue,previous studies have mainly focused on steady flow cases,and the scour pattern below submarine pipes induced by high-amplitude transient waves has rarely been *** paper reports the results of 40 experimental runs on transient wave-induced scour below a model pipe in a laboratory flume under a variety of initial *** variables included the bed particle size and gradation,initial water depth,wave height,and slope of the bed *** were generated by a sudden release of water from a sluice gate,installed in the middle of the flume.A pressure transducer data acquisition system was used to record the wave heights at different time *** results indicate that,with a shallower initial depth of flow,the scour depth is relatively *** was also found that there exists a direct correlation between the induced wave height and the size of the scour *** was observed that,in clear water conditions,the size of the scour hole in coarse sediments is smaller,while in live-bed conditions,larger scour holes are created in coarser *** was also observed that at high wave amplitudes,the live-bed conditions are dominant,and consequently the bed elevation is altered.

关键词： Submarine pipe Scour hole Transient wave flume experiment Live-bed condition Sediment

Spatio-temporal deposition profile of an experimentally produced turbidity current with a continuous suspension supply

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International Journal of Sediment Research 2022年第3期37卷 299-306页

作者： Shun Nomura Giovanni De Cesare Mikito Furuichi Yasushi Takeda Hide Sakaguchi Mathematical Science and Advanced Technology JAMSTEC Plateforme de Constructions Hydrauliques EPFL Laboratory of Food Process Engineering ETH Headquarters JAMSTEC

A turbidity current is a turbulent, particle-laden gravity current that is driven by density differences resulting from the presence of suspended sediment particles. The current travels downslope, bearing a large amount of sediment over a great distance, and forms fluvial and submarine bedforms. Knowledge of the spatio-temporal deposition profile of turbidity-deposited sediment is important for a better understanding of sediment transport by turbidity currents. In the current study, the depositional process of experimentally produced quasi-steady turbidity currents in an inclined flume was investigated using an electrical-resistance-based depositmeter. It was found that the amount of sediment deposited along the flume bottom increases linearly with time at a specific rate, and decreases exponentially in the downstream direction. Inspired by this observation, the mass conservation law was modified for the suspension layer and a simple theoretical model was proposed involving two parameters, the initial sedimentation rate and the decay constant. The proposed model reproduces the observed data from the flume experiment with high accuracy, and is consistent with the sediment transport distance of a natural example, the Bengal Fan. It was concluded that the two parameters that govern the sedimentation process are the key to estimating the deposition profile of fluvial systems.

关键词： Turbidity current Deposition process Mass conservation law Electrical-resistance-based depositmeter Spatio-temporal investigation flume experiment

experimental study on the bank erosion and interaction with near-bank bed evolution due to fluvial hydraulic force

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International Journal of Sediment Research 2015年第1期30卷 81-89页

作者： Ming-hui YU Hong-yan WEI Song-bai WU State Key Laboratory of Water Resources and Hydropower Engineering Sciences Wuhan University

Bank erosion is a typical process of lateral channel migration,which is accompanied by vertical bed *** a main sediment source,the failed bank soil may directly cause the increase of sediment concentration and considerable channel evolution in a short *** paper presents an experimental study on non-cohesive and cohesive homogenous bank failure processes,influence of the failed bank soil on bank re-collapse,as well as the interaction between bank failure and near-bank bed evolution due to fluvial hydraulic force.A series of experiments were carried out in a 180° bend rectangular *** results reveal the iteration cycle between bank erosion and bed deformation:undercutting of the riverbank,slip failure of the submerged zone of the bank,as well as cantilever failure of the overhang,failed bank soil staying at bank toe temporarily or hydraulic transportation,exchange between the failed bank soil and bed material,bed material load being re-transported either as bed load or as suspended load,and bed *** as bank failure,the mixing of failed bank soil and bed material is more severe near the curved flow ***,non-cohesive bank failure tends to occur near the water surface while cohesive bank failure near the bank *** non-cohesive dense(sandy) soil,the bank erosion amount and residual amount of failed bank soil on the bed increase with the near-bank velocity or bed *** for cohesive soil,only bank erosion amount follows the above *** results are expected to provide theoretical basis for river management and flood prevention.

关键词： Bank erosion Near-bank bed evolution Hydraulic transport Interaction flume experiment