Abstract:The objective limitations and the difficulties of further development in hydrologic experiments are discussed. The importance of improving hydrologic survey techniques, methods and some key development aspects are also discussed. The reasons that the data-intensive paradigm is applicable to hydrology study are pointed out, and a tentative idea is suggested based on the analysis of the background of data-intensive paradigm in scientific research and its great vitality. Hydrologists are appealed to take the chance to put data hydrology on the agenda and in an important position, while at the same time, to develop hydrological remote sensing energetically and deeply. In the future, under the driving force of data-intensive paradigm, hydrology will be mutual complementation and integrative development with physical hydrology, random hydrology, simulation hydrology and data hydrology.

Abstract:Based on the measured hydrological and topographic data of the Three Gorges Reservoir, the dynamic reservoir capacity in the mainstream was calculated by a one dimensional numerical model, and the dynamic reservoir capacity of each characteristic reaches was fitted after comprehensive analysis. The study shows that the dynamic reservoir capacity in the mainstream of the Three Gorges Reservoir can be expressed approximately with good accuracy through the water level relationships from representative hydrological stations. In the case of a constant water level in the front of the dam, the dynamic flood control capacity decreases with the increase of discharge, and the difference between dynamic and static flood control capacities increases with the increase of discharge.

Abstract:From data analysis and numerical validation, the influence factors of water level dropping in Nanchang reach of Ganjiang River were analyzed in the aspect of the water and sediment discharge from the upstream, water level dropping of the Poyang Lake in the downstream and the riverbed deepening in Nanchang reach. It shows that riverbed deepening caused by the large scale of artificial sand mining is the main influence factor for the water level dropping in Nanchang reach. Water level dropping of the Poyang Lake is another factor and the dropping amplitude varied from the amplitude of the water level in the downstream, the distance from the Poyang Lake and the river discharge. In addition, the water level drop in the downstream is also evidently affected by local high beach bed in the dry season. Self-scouring only accounts for 1. 0%~3. 5% of the riverbed deepening, which has limited impact on the water level dropping in Nanchang reach.

Abstract:A new lake treatment concept is proposed for Dongting Lake based on the idea of central lake reservoir, which includes transforming lakes into reservoirs, waste water cleaning and diverting, flood storage and sewage discharge, and running water never becoming putrid. The impacts of the central lake reservoir construction in the West Dongting Lake on flood, water replenishment and water environment are numerically investigated by a two-dimensional hydrodynamic model, and the feasibility of its application is also discussed. The results show that the flood storage capacity of the central lake reservoir can greatly reduce the peak flood elevation in West Dongting Lake, reducing its flood control pressure. Water replenishment from the central lake reservoir in the dry season can also efficiently increase the water level in Kaihu channel to improve the navigation condition. Meanwhile, water replenishment from the central lake reservoir can greatly increase the flow velocity in Kaihu channel and Xiangjiang River downstream channel, resulting in enhanced water exchange and better water environment.

Abstract:1D rectangle spur dike, 2D trapezoid spur dike and 3D deposit body model were used to investigate the influence of structures with different dimensions on water surface profiles and 3D time-mean velocities under the same flow condition by flume experiments. The experimental results show that, (1) for the same occupied width ratio of the structures, the actual flow resistance area induced by the trapezoid dike is the largest and it has the most intensive resistance impact on the upstream flow due to the existence of the first recirculation zone. The rectangle spur dike and deposit body have a medium and least flow resistance impact, respectively. (2)With the same flow resistance area ratio(flow resistance discharge ratio), the rectangle dike has a better ability to accelerate the flow along the channel near the narrowed cross section and detour the flow to the bank than the trapezoid dike, but the flow around the trapezoid dike has a higher vertical velocity. (3)When the length of the structures keeps the same along the flow direction, the longitudinal, horizontal and vertical velocities around the deposit body are lower than that around the rectangle dike due to its smaller maximum cross-sectional area. As a result, the factors commonly applied to evaluate flow resistance characteristics, such as the occupied width ratio, the flow resistance area ratio and the flow resistance discharge ratio, cannot entirely represent the influence of the structures on river flows.

Abstract:Flume experiments were carried out to study the effect of vegetation on wave attenuation and turbulence. Wood cylinders were used to simulate the rigid vegetation. Wave height attenuation and flow structures were analyzed for five vegetation configuration types and four kinds of wave conditions. The results show that vegetation density has great influence on wave attenuation. With the wave propagating inside the vegetation zone, the rate of wave attenuation decreases. The attenuation of short waves is larger than that of long waves. The relationship between the drag coefficient of vegetation(C_D)and Keulegan-Carpenter number(K_C)is fitted with a quadratic function, and C_D decreases with the increase of K_C with a decreasing variation rate. Turbulent kinetic energy(E_TK)in the vegetation zone increases with the wave height and vegetation density. E_TK induced by submerged vegetation is larger than that by emerged vegetation. Under the effect of submerged vegetation, E_TK increases from the vegetation bottom to water surface, and the highest E_TK occurs near the top of vegetation canopy.

Abstract:The current disaster assessment indicators are not comprehensive and systematic enough to evaluate the impacts of social, economic and environmental aspects, and the determination of index weight and grade assessment standards is subjective. As a result, a comprehensive evaluation index system of natural disaster grade assessment is concluded covering social, economic and environmental aspects. A cloud-based weight determination method and a grade assessment model of disaster situation are proposed and have been applied to six typical rainstorm and flood events. The results of analysis and evaluation show that the weight determination based on the cloud model can integrate all the assessing information from experts objectively. The assessment method can achieve evidence-based standard of disaster grades and determine the grade level objectively and reasonably.

Abstract:To analyze the seepage problem of groundwater during the development of potash salt mining area in Dongtai, Laos, a geotechnical seepage-erosion-stress coupling experimental device was used to study the permeability evolution of the rock salt collected from the mining area under pressure-dissolution coupling effect. The experimental results indicate that the average seepage velocity of the rock salt samples decreases first and then increases with the increase of hydraulic gradient during the experiment. The permeability coefficient of the rock salt samples decreases rapidly with the increase of hydraulic gradient at first, then increases slowly and finally tends to be stable. The permeability evolution of the rock salt is affected by both dissolution and confining pressure. The dissolution promotes the formation of seepage channels and enhances the permeability of the rock salt sample. The confining pressure makes the seepage channel close and reduces the permeability of the rock salt sample. It is a process of mutual promotion and mutual inhibition. Dissolution can promote the development of inhomogeneous concentrated seepage channels interior of the rock salt specimen, profoundly affecting the permeability evolution of the rock salt.

Abstract:To analyze the foundation stability of the circular soil cave with double holes, the complex stress function is obtained for a single hole by the Cauchy integral method. The stress of any point in the soil layer under bipolar coordinates is derived based on the Schwarz alternating method by two iterations. The maximum and minimum stresses of the soil are obtained by stress coordinate transformation and the Mohr-Coulomb strength criterion is used to determine the stability state of the most dangerous point of the soil cave. The calculated results in this paper are compared with the exact analytical solutions and the ABAQUS numerical simulation results. Application to an engineering example proves that the Schwarz alternating method has higher precision. The stability coefficient is introduced to analyze the stability of the double-hole soil cave from three aspects, the lateral pressure coefficient, the ratio of the soil cave radius and the relative position of the soil cave. The results reveal that the stability coefficient of soil cave has a linear positive relationship with the lateral pressure coefficient. It decreases nonlinearly with the increasing value of the ratio of the soil cave radius and remains unchanged first and then increases linearly with the increase of the relative position of the soil cave.

Abstract:Current numerical models for studying the stability of underground cavern group are simplified 3D models that are only composed of the main powerhouse, the main transformer chamber, the main electrical wire hall, part of the diversion tunnel and tailrace tunnel. The influence of the excavation of other caverns is usually ignored, leading to the inconsistency with realistic project conditions. In this study, a 3D FEM model of the Panlong Power Station, considering all the caverns as well as a 3D simplified model only including part of the cavern was built. The deformation characteristics and stress states of the cavern group during excavation were studied using 3D nonlinear FEM. The results show that the simulated distributions of deformation field, stress field, and plastic zone between the two models are similar but the magnitudes of the results from the 3D FEM model considering all caverns are generally higher than that of the simplified model. The difference between the two simulated horizonal displacements of the upstream wall can reach 19. 5%. Therefore, from the point of view of engineering safety, it is recommended to choose 3D FEM simulation models considering all caverns to perform stability analysis for underground cavern group excavation.

Abstract:To ensure long-term and safe operation for Shuibuya CFRD Project, water quality of the reservoir, composition and causes of the attachments on the concrete face and the strength condition of the concrete face were analyzed. On this basis, causticity evaluation for face slab concrete caused by reservoir water and attachments was completed. The results show that reservoir water is non-corrosive to both the face slab concrete and the steel bars. The main ingredients of the attachments on the concrete face are calcite and quartz, which are basically non-corrosive to the face slab concrete. The strength loss of the face slab concrete has little change, indicating a good operation condition. Considering aesthetics and long-term safety, it is suggested that the attachments on the concrete face should be cleared regularly.

Abstract:To accurately predict the large-scale ground vibration induced by flood discharge and energy dissipation of high dams, a method combining prototype observation with hydraulic model test is proposed. Excitation and response were obtained separately in the present method, avoiding the difficulty of accurately simulating the propagation process. The correlation between excitation and response is used to predict the ground vibration. The results show that the vibration process is characterized with low-frequency, continuous, stationary and random features. The main frequency of the ground vibration is 1. 5Hz to 3. 5Hz, closely related to the geological conditions, flood discharge and operation modes. There is a positive correlation between the ground vibration response and the surface fluctuating pressure which is obtained by filtering and synthesizing of the point fluctuating pressure in the model test. Under different discharge levels and operation modes, the error between the predicted and the measured response values is within 10%, indicating a high prediction accuracy for the proposed method.

Abstract:Real granular materials tests are commonly conducted to investigate the relationship between cushion particle’s shape, particle size distribution, porosity and bursting and puncture of the geomembrane on the cushion. However, rules of statistical significance are difficult to be obtained due to the randomness of the sample and the uncontrollable conditions of the experiment. To solve this problem, a stochastic reconstruction model of granular cushion is established based on Voronoi diagram, in which the particle size distribution and porosity of the model are controlled by adjusting the parameters of the random process. Statistical analysis was conducted for the shape parameters of the particles in the stochastic reconstruction model and their significance test between the real particles was also performed. The results show that the particle shape of the stochastic reconstruction model is close to that of the real cushion particles. The proposed model can be used to further study the bursting possibility of geomembrane on particle cushion and the relationship between the shape of the cushion particles, the particle size distribution and the porosity.

Abstract:Effect evaluation is a key problem in the post evaluation of reinforcement for dangerous hydraulic projects in China. Aiming at the index system and the methodology for comprehensive evaluation, the state of art in reinforcement effect evaluation for dangerous hydraulic projects are summarized in the aspect of macro qualitative evaluation, single efficiency evaluation, comprehensive evaluation index system, index weight, grade division and determination of comprehensive evaluation, etc. Future studies should be focused on establishing the comprehensive evaluation index system which considers both the general and special reinforcement effects. In addition, cloud models of remark set, evaluation index weight and membership degree should be established. Meanwhile, the sustainable development effect should be strengthened in the reinforcement effect evaluation.

Abstract:Concrete leaching experimental investigations, main influence factors during the leaching process and the leaching mechanisms are concisely reviewed, analyzed and discussed. The results show that contact leaching and penetration leaching are two major macroscopic leaching test methods. Leaching speed can be accelerated by electrochemistry or chemical reagent method and the test period can be effectively shortened. The combined utilization of the microscopic experimental methods such as CT, SEM and XRD is an effective way to investigate the leaching mechanisms for cement-based materials. Water cement ratio and water quality are the main factors of the leaching process. The concrete contact leaching is a process caused by the successive dissolution of CH, C-S-H and other compounds, with the diffusion induced by the concentration gradient. Considering the high hydraulic gradient working conditions of hydraulic structures, leaching mechanisms of hydraulic concrete under multi-factors, penetration leached hydraulic concrete models, and the cracking-fracture propagation problems of penetration leached concrete face slabs under cracking conditions need further investigation.