Applied Mechanics and Materials Vols. 212-213

Abstract: The river reach in the center of Chongqing City lied in the fluctuant backwater of the Three Gorges Reservoir, and it was also the junction reach of the Jialing River to the Yangtze River. It’s flow conditions and sediment movement was very complex. In the Three Gorges Reservoir 175m experimental operation period, the inherent laws of flow and sediment transport of river reach was changing under reservoir regulation. Prototype measured data for 20 years was analyzed at Jiulongpo, Zhuerqi, Jinshaqi and Cuntan sections. The results show that the association with the local flow were strong for the average sedimentation intensity in Flood season and the average erosion intensity later Flood season at the four sections. Different sediment erosion and deposition intensity corresponding to the flow was presented. According to the curve of discharge and cross-section mean velocity at Cuntan hydrologic section, the cross-section mean velocity corresponding to each flow is determined. On this basis, Sediment erosion and deposition change of river reach is analyzed at Three Gorges Project 175m operation periods.

Abstract: Saline intrusion is important for ecological reasons as well as water extraction purposes in estuaries. The distance of saline intrusion depends on a number of factors, including river discharge, tidal and wind mixing and gravitational circulation. In this paper, a simple and effective prediction model is derived for the saline intrusion at high slack water in a well mixed, funnel-shaped estuary whose cross-sectional area decreases exponentially (with convergence length a) with distance, x, inland. The model study shows that a graph of salinity against exp (x/a-1) is a straight line, with the slope proportional to the mixing coefficient Dx. The prediction model is presented and validated in Modaomen estuary, one of estuaries of Pearl River Delta in south China and the model results are compared, with good agreement, to the measured data. By analyzing the relationship between the salt intrusion length and tidal range, it is concluded that the optimal time of increasing runoff discharge to prevent saline intrusion is 2 to 3 days before neap tide.

Abstract: Recharge well with filter layer is a sort of valid recharge facility in groundwater reservoirs, which is constituted by recharge well and recharge pool. The main problems of existing recharge well with filter layer are analyzed in this paper; the main reason of these problems is concluded as the defective design of the wellhead structure; the optimal outer design method of recharge pool is studied. In order to increase single-well recharge volume, improve anti-silt and anti-rush capability of recharge well and save sand-gravel materials, geotextile material and hard wall material are adopted; a new sort of geotextile recharge well with filter layer is developed. The theoretical formula of single-well recharge volume is deduced.

Abstract: Based on a test of wind carried sand roadbed in the west bank of Qinghai Lake, Rayleigh wave method is introduced to measure roadbed compactness of the specific soil in China, and analysis is conducted to find correlation of Rayleigh wave velocity (VR) vs. the blow count (N10) of dynamic cone penetration, then a regression formula is presented.

Abstract: The formation cause of sink reach’s river pattern of the alluvial river flowing into the lake was studied by the experiment method. The results showed that: the change of lake level was the important formation condition of the alluvial river’s sink reach. The sediment concentration, the riverbed gradient were the major factors influencing the river pattern’s evolution of the sink reach. When the sediment concentration of upstream river was less, the sink reach was inclined to form a straight river, and with the increase of the sediment concentration, the bifurcated river was the chief river pattern. When the sediment concentration increased to a certain value, the sink reach was inclined to form a wandering river. When the riverbed gradient was less, the sink reach was inclined to form a bifurcated river, and with the increased of the gradient, the wandering river was the main river pattern. The sediment diameter affected channel evolution, but the influence extent was less.

Abstract: In the present paper, the definition of fluid mud was reviewed in detail. The difference of fluid mud and sediment-induced density current were also discussed from several aspects, including physical characteristic, forming process and conditions. As far as the formation condition of fluid mud concerned, there are three key factors which are “weak hydrodynamic condition, high sedi-ment concentration, and obvious negative terrain”. Similarly, also three factors are very important for the formation condition of density current, which are “little velocity, large density difference and deep water depth”. Obviously, there exists a one-to-one relationship between formation conditions of fluid mud and those of density current. Thus a quantitative method for analyzing the formation condition of fluid mud was established reasonably by means of the formula describing sediment-induced density current. Consequentially the critical sediment concentration for fluid mud formation can be estimated by using the method. And the navigation channel of Lianyungang harbor in Jiangsu Province, China, was taken into account as a case study. The results show that the formation condition of fluid mud will be more easily satisfied with the increase of the approach channel depth in Lianyungang Harbor. The method and main conclusions can be used as reference for similar harbor project in muddy coast regions.

Abstract: It is vital to obtain the carrying capability formula of suspended sediment in wave-current coexistent system to develope sediment numerical models in coastal areas. We are looking for a formula, the results of which are more accurate in calculating the natural water-flow’s sediment-carrying capability.The key problem is how to reseach the carrying capability of suspended sediment in wave-current coexistent system scientifically.The auther of this paper points out the three points in the research of the carrying capability of suspended sediment in wave-current coexistent system:(1)research methods;(2) selection of the measured data;(3) fitting methods.

Abstract: A study on the development and utilization of the surface water and groundwater,and an evaluation about the quality of Shiyang river has been made in this paper.The basin of Shiyang river has a surface runoff uneven distribution of the year,a periodic interannual variability and a down trend in total content.There is a serious phenomenon that the groundwater is over-exploited, the underground water level declines year by year,the dynamic general characteristics of underground water in recent years is persistent declining of underground water level.Influenced by industry water pollution,urban life water pollution,agricultural water pollution and water back,add the deterioration of the groundwater quality,groundwater salinity is increasing gradually, all kinds of harmful ion content increased year by year.

Abstract: Formulating and implementing river basin water resources allocation scheme is one of the most crucial measures to promote orderly development, efficient utilization and management, reasonable allocation of water resources. Clarifying water share for each region in a river basin and perfecting water resources allocation system can effectively contribute to achieve the social stability, eliminate the water use contradiction among different regions, realize sustainable water resources utilization and eco-social development, guarantee environment flow. It also conforms to the strictest water resources management system proposed and carried out at present of China. In order to make the readers better understand water allocation done or being done in China, river basin water resources allocation practice was summarized in this study. Institutional arrangements related to water resources allocation in China was also been summed up.

Abstract: To study the chemical weathering of the water source area of Central Guizhou water control project(CGWCP), a hydrological year observational study was carried out during May 2010 to Jane 2011 in the Yangchang hydrological station section in the Sancha River basin,in which the output fluxes and its weathering modules of the total dissolved substances(TDS) and dissolved inorganic carbon (DIC) were analyzed quantitatively.The results showed that :the weathering modules were 9.771×107g.km-2.a-1 of TDS and 7.996×106g.km-2.a-1 of DIC respectively with notely seasonal variation that 93.1% of TDS fluxes and 92.8% of DIC fluxes were output during the high temperature and rainy season from June to November 2010,as well as showing a striking decreasing trends from Sumer(6~8), Fall(9~11), Spring(3~5) to Winter(12~2).Chemical weathering modules demonstrated that significant seasonal variation of thermal and rainy conditions striking impacted karst processes had been closely related to characteristics of the watershed land surface, climatic, as well as hydrological processes.