Applied Mechanics and Materials Vols. 212-213

Abstract: Based on the experimental data of sediment particle cloud during the settlement process in the water and combined with the existed sediment settling velocity formulae, a new formula for calculation of the settling velocity of sediment particle cloud is proposed by the introduction of the characteristic particle size of sediment particle cloud ( D' ). By using experimentally measured settling velocity values of sediment particle cloud to verify the settling velocity values of sediment particle cloud which calculated by using this new formula, the results show that the calculated settling velocity values using this new formula are closer to the experimental values.

Abstract: Jianli Reach has long been exposed to labile main flow and the frequent translocation between the main channel and the lateral branch. To investigate how the long-term process of flow-sediment influences the adjustment of river channel pattern, monthly time series (1951-2009) of runoff and sediment load at Jianli hydrological station of Yangtze River were analyzed using three methods: R/S analysis to estimate Hurst exponent, Mann-Kendall method and the time series anomaly analysis. The result shows that on 1 year time scale, the values of Hurst exponent are indicating persistence, that is to say, the trend of runoff and sediment in the future will generally be the same as the past, and the persistence in runoff series is stronger than that in the sediment load. The period of oscillation in annual runoff and in sediment load is about 30 years. The result of Mann-Kendall test shows an abrupt change point of runoff time-series at 1967 and an abrupt change point of sediment load time-series at 2003. And during the flood season, the values of Hurst exponent still indicate persistence, which is weaker than that in whole year correspondingly.

Abstract: Fractal theory is used to describe river bed form. Based on improvements in some aspects of Surface area – Scale Method, such as, estimation of surface area, boundary treatment and so on, the calculation method of surface fractal dimension with irregular boundary is obtained, and the new method has good application on the bed surface fractal dimension calculation. The fractal characteristics of river bed surface morphology are discussed by combination with river-pattern, river regime, river process and changes of BSD. BSD can be used to study some related problems, such as analysis of river regime, distinction of river pattern, calculation of river resistance and so on.

Abstract: The seepage analysis is an important part of the earth-rock dam design, it is often calculated by using finite element method. In the infinitely deep permeable foundation construction of the dam, foundation deep permeable layer, preferably using the boundary element method to calculate. In this paper, the boundary element method is used to establish the construction of earth-rock dams in the blanket impervious seepage calculation model in the infinitely deep permeable foundation, and verify the feasibility of the model and provide reference for designers.

Abstract: An artificial reservoir will be formed at the dam upstream in a large hydropower station after the station put into use, and with water area expanding, the local climate will change. This paper takes mesoscale meteorological numerical model WRF to simulate a certain hydropower station in Sichuan to obtain the impacting situation of the local climate after the water storage. The result indicates as follows: firstly, the wind field has been greatest changed after the water storage. Except in the winter, we can found obvious lake-land breeze in the spring and the summer and the flow field is very evident; secondly, the temperature is rising or falling; except for a little change in the spring, the average temperature falls 1.27°C in the summer but rises at 1.28°C in the winter. In addition, the humidity around the reservoir is changed distinctly; the average humid degree rises mostly at 4.56% in the winter, moderately at 2.25% in the spring but a little change at 0.94% in the summer. It is since the climate factors have been changed that the concentration field of atmospheric pollutants which generated by the industrial and mining enterprises around the reservoir has been changed at all.

Abstract: In order to study the influence of the navigation improvement project in the Qingyi River, on flood control of the complex river network, the water level variation of the key control stations in Shuiyang, Qingyi and Zhanghe river basins, flood diversion variation of middle reach of Shuiyang stem and flow pattern in the flow field before and after construction of the project using Mike11 model, under the conditions of designed flood and excessive standard flood. The results show that after construction of the project,the water levels at the control stations are decreasing or constant and the flood diversion of middle reach of Shuiyang stem decreases. So the project is beneficial to the flood control of the basins.

Abstract: Hetao irrigation area in Inner Mongolia is one of the four major irrigation areas in China, seasonal frozen soil is widely distributed in this area. Irrigation channel engineering experiences seriously freeze-thaw cycle many times in the long winter, its maintenance is the important and difficult point all long in irrigation channel engineering of Hetao irrigation area. For this, we analyze the moisture migration and law of frost heave characteristics of seasonal frozen soil in Hetao irrigation area.

Abstract: Hydrologic cycle was the supporter of pollution matter transportation, and the transferring of agricultural non-point source pollution from land to water has great relationship with hydrologic process. As part study of agricultural non-point source pollution matter transferring mechanics in small watershed, we studied the soil water movement, overland flow producing and confluence mechanism at the hillslope and watershed scales during storm events in humid area. This study monitored the overland flow, soil moisture, groundwater and the stream flow at outlet of the watershed during two storm events (July 19th 2008 and July 30th 2009), analyzed the rain-runoff producing patterns under different conditions and their impact factors. In humid area, soil water movement had three patterns, rainfall infiltration, lateral subsurface flow and groundwater rising, their ranges of influence depths were decided by the rainfall amount, duration and intensity, antecedent conditions and the soil physical characteristics. The overland runoff was infiltration excess runoff at the leading portion of the event, and changed gradually into the mixed patterns of infiltration excess runoff and saturation excess runoff. There was a large amount of regression water on the falling limb of the stream flow. The sources of the stream flow at the outlet of watershed contributed much to the non-point source pollution transportation pathways.

Abstract: Precipitation-runoff partitioning of small basins plays an important role in the non-point pollution study. This study analyzes the contribution of precipitation and rainfall intensity in a basin scale to pollutants(e.g. nitrogen, phosphorus) migration by monitoring rainfall and runoff responses in Meilin watershed. According to the field data, the concentration of nitrogen keeps an increasing trend with the increase of rainfall amount, while phosphorus seems not so evident. Intense rainfall has a fierce scouring effect on the pollutants which have a large using amount such as total nitrogen in the steep experimental field, thus leading to a sudden decrease of pollutant concentration. After the intensity is weakened, pollutant concentration gradually goes up due to the dissolving effect of runoff.

Abstract: This paper analyzes the circumstance of the sharp cutoff of water and sediment in He-Long reach recently, discusses the cause of the change of water and sediment. The study shows that, the change of underling surface and the rainfall without runoff are the primary reason for the sharp cutoff of water and sediment, if the rainfall condition changes, especially under the rainstorm which in the large area, with high strength and last for long time, the accumulated and secluded sediments could make the sediment yield increase sharply, the circumstance of sharp cutoff of water and sediment would change.