Discussion on Treatment Countermeasure in Bedrock Area on Loess Plateau
BI Ci fen
(Bureau of the Upper and Middle Reaches of Yellow River)
Abstract: The bedrock area in loess plateau is a core source of coarse sand.It is also one of the sources of sand storm and dust in China.If you want to eliminate the damage of coarse sand siltation on the channel of lower Yellow River,to curb the extension of sand storm and dust, to realize good cycle of local ecology and economy, the concentrated treatment will play a critical role.This paper is based on the result of plant¡°flexible dam¡±experiment in soft-rock area.It presents an operational treatment model in the area so as to accelerate ecological environment recovery progress.
Key words:
loess plateau; bedrock area(source of coarse sand); ecological recovery; treatment model
River Course Shrinkage and Flood Control of the Lower Yellow River
HUANG Jin-chi
(China Institute of Water Resources and Hydropower Research)
Abstract: An obvious change of incoming water flow and sediment of the Lower Yellow River has contributed to the river course shrinkage.Data analysis shows that the discharge capacity reduction mainly occurred in the main channel.Some concept analysis illustrated that the flood problem may be more serious than previous situation but the flood may have a different form.For the new situation in the Lower Yellow River,the main problems for the flood prevention are on the adjustment of incoming water flow and sediment,regulation of river course controlling projects,and floodplain management.
Key words: river bed regulation; river course shrinkage; flood control project
Discrete Particle Dynamics Model for Simulating Sediment Transport by Wind
Sun Qi-cheng,WANG Guang-qian
(Dept.of Hydraulic Engineering,Tsinghua University)
Abstract:A discrete particle dynamics model of two-dimensional sand transport by wind has been developed in which the motion of grain is considering individual particle motions while velocity distribution is given according to experimental observations.The above model has been used for simulating the phenomenon of 9000 grainsmovement,resulting in ripples,saltation paths above surface,which are all in good agreement with the known experimental results.Exchange between saltation and surface creep along sruface is also measured,which is helpful for revealing the intrinsic mechanism of sand movement,but very hard to the commonly used methods and regular experimental measurements.Therefore,the discrete particle dynamics model can authentically simulate sand movement and offer more detailed information,which could be applied in a wider suitable range in comparison with previous the commonly used models.
Key wrords:sediment transport,snad flow structure,DEM(discrete element model);computer simulation
Longitudinal Flux Variation of Falling Sand after Certain Cross-section in Air
NI Jin-ren1,3, LI Zhen-shan2,3
(1.Center for Environmental Sciences,Peking;2.Department of Hydraulic Engineering,Tsinghua
University;3.The Key Laboratory of Water and Sediment Sciences,Ministry of Education)
Abstract: Based on the "saltation-diffusion" concept for sand grain motion in air,an experimental study is carried out on the longitudinal profiles for sand falling flux after certain cross-section.The profiles were found to be determined by three key parameters such as sand falling flux at reference cross-section,averaged maximum saltation length for sand grains and the "saltaion-diffusion" index.An approximated relation was used,which could describe the experimental results satisfactorily.Longitudinal flux profiles were measured by means of horizontal array trap for a variety of air flow velocities and sand grain sizes.It was found that the averaged maximum saltation length for sand grains increases with increasing airflow shear velocity and sand grain size,whilst "saltation-diffusion" index varies in the reverse trend.
Key words: airflow with saltation; sand falling flux; saltation-diffusion index
Pneumatic Transport of Wet Particles in Horizontal Pipe
LIU Shuang ke1, XU Xu chang1,
WANG Guang qian1, Takahashi hiro2
(1.Tsinghua Univercity;2.Tohoku University)
Abstract: Three sizes of particles of 0.99mm,1.9mm and 2.9mm mean diameter were conveyed as wet-particle air mixtures through 25.4mm and 30mm in horizontal pipe. When rate of water flow was a range of 0.55-0.67m/s and rate of air flow was a range of 0.4-3.2m/s, pressure drops and limit deposit velocity were measured over a range of slurry concentrations to 21.7% by volume. The principal flow patterns studied were a regime of gas-liquid-solid slug flow ¡£The follwing conclusions were obtained through this experiment. Firstly, pressure loss of pneumatic transport of wet-particle was smaller than slid-liquid two phase flow and pneumatic transport of particle; secondly, the range of limit deposit velocity of pneumatic transport of wet-particle was measured.
Key words: wet-particle; pneumatic transport; limit deposit velocity; pressure loss; gas-liquid-solid slug flow
Preliminary Study on the Sediment Concentration Forecasted with Fuzzy Neural Network in Hangzhou Bay
SONG Li-song
(Zhejiang Institute of Estuary and Coast)
Abstract: This paper presents a new network named AFNN (Adaptive Fuzzy Neural Network) for simulation of continuous sediment concentration on the basis of tidal flow-sediment model.In this AFNN,S is considered as output,the value of the instant (U¡¢V¡¢H) and at previous instant (S¡¢U¡¢V¡¢H) are considered as input,the fuzzy relationships between sediment and various factors are discussed by the field data training and learning with fuzzy clustering and neural network in Hangzhou Bay.The results of primary application shows the network is only for real-time forecast or short-term sediment concentration forecast,which indicates sediment forecast is difficult,the forecast scale is very finite and the long-term sediment forecast is unpractical.
Key words: sediment concentration; fuzzy clustering; fuzzy neural network
Debris Flow Simulation for Design of Highway Cross-Culverts
WU Bao sheng
(Department of Hydraulic Engineering, Tsinghua University)
Abstract: A study on the design of highway cross-culverts in a debris flow potential area along the Snowmass Canyon segment of SH-82 is presented. Considering the characteristics of the drainage network and the highway cross-culverts, the Federal Highway Administration's BRI-STARS model is enhanced to simulate surface profiles for debris flows. Appropriate sizing of highway cross-culverts is provided based on the results of the model simulations for various approaches utilizing both clear water and debris flow techniques. It is shown that the traditional clear water modeling results in considerably undersized culverts for debris flows. The modified BRI-STARS model was verified using field data and was shown to be an effective tool in the design of cross-culverts for debris flows.
Key words: debris flows simulation; cross-culvert; BRI-STARS; stream tube model
Analysis on Bank Failure and River Channel Changes
XU Yong-nian, LIANG Zhi-yong, WANG Xiang-dong, LI Wen-wu, DU Ying-qiAbstract: Bank is often scoured by river flows and protection has to be made. Locations and mechanism of bank erosion should be better understood in order to protect bank failure thoroughly. This paper made a general description for bank failure in alluvial streams, and classified the bank failure into four types as shown in Fig.1 to 4. Thus in this paper presented an example analysis for Jiujiang reach located in the lower part of the Changjiang River, and pointed out that some places of the left bank of the central bar is suffered erosin or will be under erosion within a near future, and suggested that such places of unstable bank should be protected as soon as possible.
Key words£ºJiujiang reach of the Changjiang River; river channel changes; bank failure
Abstract£ºBased on the field observed hydrologic and sediment data at Huanghe River estuary in flood season in 1995, the conclusion was drawn that as long as total density of turbid water is greater than 1.020 kg/m3, the density current can flow continuously beneath the clear water. Sediment concentration and velocity vertical distribution curve may be represented by regression functions based on regression analysis of materials about sediment concentration, velocity and depth at different hydrometric stations. While sediment density current exists, vertical distribution of sediment-concentration is in unbalanced way. The deeper the water is, the larger the increment of sediment concentration will be. The velocity distribution curve is different from that which have been measured in reservoir, lake or laboratory flumes in the past, the velocity model on sediment density current at Huanghe River estuary is an unique model: the velocity doesn't change when water depth changes.
Key words: Huanghe River estuary£» sediment density current£»sediment concentration£» viscosity coefficient
Abstract: The mechanization of dredging has been adopted in the channel excavation dredging and dykes reinforcing work in the reach of the Yellow River mouth. Owing to arid climate, car running and wind forces etc., wind-sand pollution influenced the surrounding environment on a certain extent. This paper studied the incipient motion and transport of wind-sand on roads by means of measured data and theoretical analysis, proposed some harnessing measures and provided some experiences for a large scale of channel excavation dredging in the future.
Key words: channel excavation dredging; wind-sand; environment; dykes reinforcing
Discussion on the Modes of Land-clearing in the Qinling-Bashan Mountainous Region
MA YongAbstract: This paper analyses the rainfall and conditions of arable land in Zhenba County,Shaanxin Province, the modes of forestation and land-clearing in the Qinling-Bashan mountaionous region, and discusses the scope of application and design of fish-scale pits,horizontal ditch, and horizontal level, and suggests that horizaotal level land-clearing should be adopted.
Key words£ºforestation; land-clearing; the Qinling-Bashan mountainous region; discussion
Study on the Runoff Generation Process on the Slope with Numerical Method
CHEN Li, LIU Qing-quan, LI Jia-chunAbstract: In this paper,a numerical model of runoff generation on the slope is presented.The one dimensional kinematic wave theory combined with the Green-Ampt infiltration model revised twice by Mein & Larson(1973)and Chu(1978)is used in it.The effectiveness of the model is tested by some experimental data.Further more,extensive situations are calculated and the dynamic laws of main parameters,including rainfall intensity,initial moisture content,infiltration rate,resistance,slope length and slope gradient,are analyzed.Some valuable conclusions are put forward.
Key words£ºinfiltration; runoff generation; slope, dynamic
YAO Wen-yi1, HOU Zhi-jun1, LIU
Yue-lan1, LIU Shu-li2
£¨1.Institute of Hydraulic Research, Yellow River
Conservancy Commission;
2.Planning Bureau, Yellow River Conservancy Commission)
Abstract: The deposition reduction effect in starting works on river dredging and dike strengthenning between Zhujiawuzi and Xihekou in the Lower Yellow River has been studied through river engineering model experiment. It is shown from the analysis that there are some deposition reduction effects,the ratio of sediment dredging amount to deposition reduction amount is 0.76 or so in a certain period and under the conditions of experimental water-sediment after river dredging;the back-deposition amounts in the dredging reach have great influence over the effect of river dredging for deposition reduction.Due to the characteristics of water-sediment and complexity of fluvial process in the Yellow River,many problems of key techniques need to be studied further.
Key words£ºflood control and deposition reduction; river dredging and dike strengthenning;Yellow River
Review of Properties of Hyperconcentrated Flow
LIU Zhao-cun, XU Yong-nian
(Sedimentation Department IWHR)
Abstract: Compared with low concentration sediment flow, hyperconcentrated flow has its specific properties. Not only are the properties such as resistance characteristics, velocity distribution, fluctuating intensity distribution, energy distribution in the flowing process of hyperconcentrated flow specifically reviewed but also the similarities and differences between the low concentration sediment flow and hyperconcentrated flow are investigated and studied as well.
Key words: hyperconcentrated flow; property; low concentration sediment flow
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