Abstract:In order to reasonably synthesize the carrying capacity of regional water resources by the four elements of water quantity, water quality, water space and stream flow, a water resources carrying capacity evaluation model based on the four elements and a risk matrix(QQSS-RM)was proposed. Firstly, 48 preliminary evaluation indicators under the subsystem of quantity-quality-space-stream were constructed and the weight of each evaluation index in the four elements was calculated by expert consultation information method and genetic analytic hierarchy process. Through screening and analysis, 8 comprehensive evaluation indexes were obtained to construct the evaluation index system for the regional water resources carrying capacity. Secondly, 4 evaluation grade criteria of 8 comprehensive evaluation indexes were obtained by referring to relevant literature and expert opinions. Finally, an evaluation model of water resources carrying capacity based on QQSS-RM was constructed, which was applied to three third grade zones of water resources in the Xiliao River Basin. The results show that the water resources carrying capacity evaluation level of Xilamulun River and Laoha River, Wulijimulun River and the downstream of Xiliao River are overloaded, critical overloaded and overloaded respectively, showing a poor water resources carrying capacity of the Xiliao River Basin. The evaluation results are basically consistent with the current status of the Xiliao River Basin, indicating that the QQSS-RM model has better application value in regional water resources carrying capacity evaluation.

Abstract:There are many meandering rivers in the source region of the Yellow River. From the upstream to the downstream, four meandering river groups can be identified, including Maduo-Dari grassland, Zoige basin, Gannan grassland and Huangnan grassland. Combined with remote sensing imagery and field investigation, the spatial distribution, planform characteristics and boundary conditions of the meandering rivers were studied. The results show that the meander belts of the tributaries of the meandering river groups in the Yellow River source greater than 1 000 m in width all belong to the Zoige river group. The widest meander belt is the Black River(3 300 m), followed by the White River(2 500 m), where oxbow lakes are well developed. The Maduo-Dari meandering river group has the largest mean channel slope(0. 022)while the Zoige river group has the smallest mean slope(0. 009). The average sinuosity is largest for the Zoige river group(1. 67)and is smallest for the Maduo-Dari river group(1. 19). The mean channel slope of the meandering river groups is roughly negatively correlated with the average sinuosity. Boundary condition of the meandering river groups is composed of two-layer composite materials due to riparian vegetation. The upper layer is soil-root complex and the lower layer is non-cohesive silt-sand or gravel-sand layer.

Abstract:The geological disaster chain related to landslide dams has caused a lot of economic losses and casualties to China every year. Based on data statistics, the triggering factors and distribution rules of landslide dams in China in the past 10 years were analyzed. The results show that, there has been more than 100 recorded landslide dams in China. Earthquakes and heavy rainfalls are the main trigger factors, since they account for more than 90% of the total statistics. In terms of geographical distribution, Southwestern China is the heavy disaster-area of hazards related to landslide dams, and the landslide dam number accounts for more than 80% of the total statistics. The number of landslide dams in Sichuan Province is far more than that of other provinces, as it has suffered from the Wenchuan earthquake and the Lushan earthquake. Taiwan Province ranks the second, since there are 11 landslide dams recorded in the past 10 years due to the impact of typhoons yearly, accounting for 10. 2% of the total, followed by Yunnan, Chongqing and other provinces. In terms of temporal distribution, the number of landslide dams is basically fluctuating within the normal range except for the year 2008.

Abstract:Aiming at the undesirable flow patterns in the discharging flow of a sluice-pump station, double sills were applied in the downstream for rectification. The rectification effects and the hydraulic characteristics were explored based on RNG k-ε turbulence model and VOF method. The calculation results were verified by a physical model experiment. The results show that the sill forces the discharge flow to move laterally along the sill and form a vortex which can significantly improve the flow bias, backflow and oblique jump. The double sills can effectively reduce the wave motion, the recirculation zone, and improve the uniformity of velocity. The velocity non-uniformity coefficient decreases with the increase of the Fr number at the downstream outlets, and decreases first and then increases with the increase of the relative height h2/b and relative spacing d2/b of the second sill. By qualitatively and quantitatively comparing the mathematical and physical model results, it is found that the water surface curve and the velocity distribution are well consistent with each other, indicating that the numerical simulation of the turbulence model applied is reliable.

Abstract:In order to solve the problem of high measurement error in the condition of high concentration particles in surface velocity image measurement, the nearest neighbor matching algorithm is improved. The particle matching algorithm of multi-frame regression analysis, a particle matching algorithm for surface flow field based on regression analysis is presented. This algorithm takes the particle distance, the motion-trajectory and the movement trends into account. A linear regression analysis is applied to the coordinates of the particle center and the particle matching is accomplished through calculating the correlation coefficient to achieve the best homologous particle tracking. An improved large-scale particle image velocimetry(ILSPIV)was developed with multi-frame regression particle matching algorithm, which had been applied to the Baguazhou Island physical model. The measurement results of the distribution shape and value of for the average vertical velocity between ILSPIV and propeller-type current meter were basically the same, indicating that the particle matching algorithm of multi-frame regression analysis can improve the precision of surface velocity measurement in the condition of high concentration particles and can better meet the needs of engineering practice research.

Abstract:To understand the movement characteristics of a sudden point-source pollution in thermal-stratified reservoirs, the vertical movement of the thermal in the static thermal-stratified water was studied by experiment. The results show that the motion of the thermal is significantly different in water bodies with different temperature structures. The horizontal diffusion of the thermal is damped in linear stratified water. If the thermocline exists in the stratified water, the thermal can be retarded at the thermocline. Due to the density difference between the thermal and ambient water, Rayleigh-Taylor instability or double-diffusion convection may occur, and a finger-shaped intrusion can emerge. The vertical velocity of the thermal is positively correlated with the buoyancy but is negatively correlated with the cluster forward position and the buoyancy frequency.

Abstract:In order to deeply explore the internal law of water flow structures under the condition of vegetation lodging, experimental research on the influence of vegetation stem diameter on the characteristics of overland flow was carried out. Indoor open channel flow simulation tests were performed with a fixed slope of 1. 0%, a lodging angle of 20°, stem diameters of 2mm, 3mm and 4mm. The results show that the resistance coefficient of Darcy-Weisbach increases gradually with the water depth under the same diameter, the Reynolds number increases linearly, while the Froude number decreases as a power function. Under the same water depth, with the increase of the stem diameter, Darcy-Weisbach resistance coefficient increases, Reynolds number and Froude number decreases respectively. Moreover, if the stem diameter is increased for every 1mm, Darcy-Weisbach resistance coefficient increases 33. 76%, Reynolds number and Froude number decreases 2. 57% and 8. 33% respectively in average.

Abstract:In order to further explore the deformation mechanism of high concrete face rock-fill dams with a broken line axis, a finite element numerical model was used to simulate the rockfill body stress and strain, the face slab stress and deformation as well as the structural joint deformation for a proposed reservoir dam with 3 dam axis layout plans. The nonlinear relationship between the above change rules and the dam axis angles was analyzed, and the deformation mechanism of the concrete face rockfill dam with large angle broken line axis was discussed. The results show that the tensile stress of the face slab around the turning point of the dam axis increases with the broken line angle. The topographic conditions and the symmetry of dam body at the turning point of dam axis have great influence on the stress and deformation of the dam body. Reasonable selection of the turning point and turning angle according to topographic and geological conditions is the key to design concrete face rockfill dams with broken line axis.

Abstract:A cascade reservoir joint operation model for optimizing the hydrodynamic environment of the Chinese sturgeon spawning ground was constructed to protect the Chinese sturgeon resources and restore the hydrodynamic environment of the spawning ground. The evolution trend of the hydrodynamic environment in the spawning ground downstream of the Gezhouba dam before and after the joint operation of the Three Gorges-Gezhouba cascade reservoirs was clarified by means of data investigation and numerical simulation. Through comparative analysis of the actual operation and optimal operation of the cascade reservoirs during the Chinese sturgeon spawning period in 2010(Oct. to Dec. ), it is concluded that the Three Gorges-Gezhouba joint optimal operation can effectively improve the Chinese sturgeon spawning fitness and can optimize the hydrodynamic environment of the spawning ground while meeting the conventional operation targets of the cascade reservoirs. The joint optimal operation can increase the natural breeding probability of the Chinese sturgeon and can effectively protect the Chinese sturgeon resources.

Abstract:To solve the problem of insufficient measured runoff data for new-built or to-be-built cascade reservoirs, five comparable daily runoff series of the Lhasa River were generated by using MODSIM-DSS for the post construction scenario. The indicators of hydrologic alteration and range of variability approach(IHA-RVA)was used to analyze the hydrological regime variation of the Lhasa River during the current situation and in the planning period. The results show that the cascade reservoirs have positive or negative accumulated impacts on a single indicator. The severest changing degree for a single indicator occurs in March and October, during which the changing degree of the monthly averaged discharges are both greater than 0. 9, being regarded as a severe change. The comprehensive hydrologic changing degree(CHCD)in the current situation is 0. 21, belonging to a slight change, in which the severe changed indicators account for 7. 8% of the total number. The CHCD in the planning year is 0. 41, belonging to a medium change, and the severe changed indicators account for 28. 1% of the total number. The CHCD increases as the increase of the total storage coefficient with a slow-fast-slow increasing rate.

Abstract:Field experiment and CFD numerical simulation were performed to improve the ventilation and operation modes of Yixing pumped storage power station. Main influencing factors on air distribution including the air supply velocity, the start and stop combinations of generator units, and the modes of generator exhaust air cooling were investigated. The change rules of the energy utilization coefficient η, the temperature inhomogeneity coefficient k_T, the velocity inhomogeneitycoefficient k_u in a typical underground powerhouse floor were analyzed. The results show that under the existing design scheme, the temperature near the heat source equipment is significantly higher than the average temperature in the plant but the relative humidity near the heat source equipment is significantly lower than the average value in the plant. The air flow velocity near heat source equipment increases due to natural convection. The temperature, humidity and velocity distribution in the generator floor basically meet the design requirements, but in typical hot wet seasons, the temperature and humidity are close to the upper limit.

Abstract:In order to improve the riprap identification ability of seismic data collected by seismic reflection method, the influence of three seismic acquisition parameters, including the sampling period, the peak frequency of source seismic wave and the offset on seismic data quality by seismic forward simulation was analyzed. The results show that selection of the sampling period is related to the peak frequency of the source seismic wave, and the sampling frequency should be greater than or equal to two times of the maximum frequency of the original signal. As the peak frequency of the source seismic wave increases, the minimum thickness of the riprap that can be identified and the signal-to-noise ratio of the seismic data decreases gradually. The offset magnitude influences whether the reflected waves at the top and bottom of the riprap can be distinguished, and it also determines whether the riprap thickness can be obtained. As the increase of the peak frequency of the source seismic wave and the water depth, the maximum offset also increases. In addition, the reliability of the seismic forward simulation results was verified by the example of underwater riprap detection in Baoding polder.

Abstract:A deoxyribonucleic acid(DNA)corrosion inhibitor was prepared by dissolving a mixture of primers with a length of 20~80 bases in a nucleic acid buffer. Linear polarization and electrochemical impedance spectroscopy(EIS)were employed to investigate the effect of coexisting anions, HCO^-₃ and SO^2-₄, on the chloride-induced corrosion of reinforced steel in simulated concrete pore solution for the corrosion inhibition of DNA. After different treatments, X-ray photoelectron spectroscopy(XPS)was used to characterize the structure of the surface membrane of the reinforced steel. The results show that the DNA corrosion inhibitor has a good anticorrosive effect on the steel reinforcement. However, the presence of coexisting anion HCO^-₃ accelerates the corrosion rate of the reinforced steel. The addition of the DNA corrosion inhibitor alleviates the steel corrosion process and its rust inhibition efficiency is comparable to that of the commonly used commercial corrosion inhibitor(the main component is sodium phosphate). The presence of SO^2-₄ increases the corrosion rate of the reinforced steel, and its corrosion inhibiting efficiency is even higher than that of the commercial one under the same conditions.