Abstract:Based on the basic principles of geography and resource science, inspired by China’s Great Western Water Diversion Project and the South-to-North Water Diversion Project, by field investigation and indoor research over the past years, this paper innovatively puts forward a river-connected water diversion line, trying to solve the major infrastructure problems in water resources development and water conservancy construction in China. We believe that the scheme has six obvious advantages: strong flexibility, strong overall situation, few risks, feasible construction and strong operation, good justification, and great potential in following up research. In view of the new requirements of the current new era, authors suggest that China speed up the reconnaissance of water diversion routes, and carry out in-depth and systematic feasibility studies on joint dispatching of the Yangtze River and the Yellow River, taking electricity for water as the strategic objective of further improving water diversion in the future.

Abstract:Pettitt test and Mann-Kendall test were used to analyze the inconsistency of the annual maximum flood peak discharge sequence of the Ken Swart Reservoir, and the variant form of the sequence was determined. The consistent correction was conducted based on the theory of decomposition-synthesis, and then the annual maximum peak discharge sequence under the conditions of past and present was obtained. Taking it as the inflow process of the reservoir, the flood regulation routing was carried out according to the flood control and regulation rules, and the extreme flood risk rate of the reservoir under the two different conditions were calculated using frequency analysis method. The results show that the change point of the annual maximum peak discharge sequence occurred in 1993, whereas the overall rising trend of the sequence was not significant, and the jumping variation was the main variant form. According to the maximum water level of the reservoir under the two conditions, the check flood level(Z_d = 993. 35 m)was taken as the control index of the extreme flood control risk. The extreme risk rate of the flood control was 0. 231 23% under the past condition, while it was 0. 354 58% under the present condition. The rechecked extreme flood control risk rate of the Ken Swart Reservoir was larger than the 5 000-year check standard(0. 02%)under both conditions.

Abstract:To study the impact of wind field on the accuracy of a rain gauge, numerical simulation of the wind turbulence for a single rain gauge and gauges with Alter and Tretyakov wind shield was performed. The results show that the maximum velocity increase ratio of a single gauge on the center line can reach 19%, located 8cm above the gauge mouth. The Alter and Tretyakov wind shield can effectively reduce the intensity and gradient of the wind above the rain gauge mouth. The blades of the Alter wind shield can reduce the maximum velocity on the center line of the rain gauge by 11%. Two strong eddy regions are generated on the 90°of the main stream direction, which destroy the uniformity of the streamlines and reduce the continuity of the wind above the rain gauge. Due to the more turbulent wind field, there may be an adverse effect on snow collection. The Tretyakov wind shield can reduce the maximum speed on the center line of the rain gauge by 7%. The special angle structure of the blade makes the wind field in the collecting region more uniform, which is in favor of snow collection. The Alter wind shield is superior to the Tretyakov in reducing the wind speed and wind gradient, but the vortex core region of the Tretyakov at the top of the rain gauge is less than that of the Alter at low wind speed, which is beneficial to the precipitation collection. The diameter of the Tretyakov wind shield is about 0. 3m smaller than that of the Alter. Therefore, the Tretyakov wind shield can be improved by increasing its diameter and the number of the blades to avoid the influence on the core area of the collecting region in the condition of high wind speed. The structure of the Tretyakov wind shield can be referred to improve the Alter wind shield and the influence on precipitation collection efficiency can be explored by increasing the angle of the blades.

Abstract:In recent years, severe scour occurs near costal structures due to frequent tsunami waves and tsunami disasters can be alleviated by vegetation. PVC tubes were chosen to simulate generalized rigid plants, and solitary waves were selected to model tsunami waves. By changing the incident wave height, the length and density of the vegetation belt and the height of the seawall, the effects of vegetation on the morphological change of a coastal zone around seawall were investigated. Empirical relations were derived to describe the relationships between the area of erosion, the area of bar as well as the balanced points of scouring and silting and the length and density of the vegetation belt, wave height, the height of water surface above the seawall, specific weight and beach slope. The results show that vegetation has a powerful impact on the evolution of beach profiles. The existence of vegetation can significantly reduce the maximum relative scouring depth inshore the seawall and the scouring location moves from the dyke toe to the vegetation belt with increasing scouring range offshore the seawall. Erosion and deposition area is affected by both the incident wave height and vegetation factors, and for the same plant model, the area of scour hole and deposit sand bar increases with higher incident wave height. The hazards of tsunami wave on seawalls can be significantly weakened with an increasing density and optimum distribution of plants.

Abstract:The calculation formula of the transverse horizontal displacement of the bank slopes of a super-high arch dam caused by the reservoir hydraulic pressure was derived by elastic theory. Based on FEM, the reservoir type of the bifurcated channel was simulated and sensitivity analysis of the influencing factors on the reservoir basin and the dam was conducted. Theoretical analysis and numerical calculations indicate that the main influencing factors of the valley shrinkage are the reservoir water level and the bank slope angle. The distance from the river bifurcation to the dam and the reservoir water level are significant factors affecting the deformation of the reservoir basin and the dam. With the increase of elevation, the transverse deformation of the bank slope below the water surface increases on both sides of the banks and then decreases in the valley direction, while the bank slope above the water surface always deforms in the valley direction.

Abstract:According to the variation features of the compressed air pressure and temperature in the underground cavern of a compressed air energy storage plants, pilot cavern located in Pingjiang was investigated to explore the spatial distribution and variation process of temperature, stress and deformation in each structural component during charging and discharging process using thermo-mechanical coupling theory. The influence of the sealing material performance on the mechanical response of the underground cavern was also discussed. The results show that the temperature field in the sealing layer and concrete inner liner varies significantly due to the heat exchange between the compressed air and the cavern wall during charging and discharging process, while the temperature field in the surrounding rock changes slightly. The stress and displacement of the structural layers fluctuate significantly during charging and discharging process. The difference of the sealing material performance can significantly influence the mechanical response of sealing layer, concrete inner layer and surrounding rock. Fiber reinforced plastics was suggested to be the sealing material for Pingjiang shallow pilot cavern.

Abstract:Based on the influence of nonsingular term in Williams expansion of the stress field at a crack tip on crack propagation, a theoretical solution of stress was proposed with considering the friction effect of crack surface and T-stresses. The modified maximum tangential stress criterion was used to analyze the effect of T-stresses on crack initiation and propagation under compression loading conditions. Through the comparison of the test results and the theoretical solutions under uniaxial compression conditions, the rationality of the theoretical solution was verified by considering the three T-stress components (T_x, T_y and T_xy). The results show that for a certain crack inclination angle β, both the maximum tangential stress σ_θmax and the maximum absolute value of the shear stress τ_rθmax at the crack tip decrease gradually with the increase of the friction coefficient f of the crack surface. Both σ_θmaxand τ_rθmax decrease first and then increase with the increase of the lateral pressure coefficient k. The possibility of shear crack is higher with larger k and β. The results also reveal that the T-stresses can be controlled to keep the crack growth direction away from the dangerous direction and the overall structure fracture can be effectively stopped or delayed.

Abstract:Concrete specimens of different strength grades, maximum aggregate particle sizes and specimen sizes were dried in an electro-thermal constant temperature blast oven. The specimens after drying were placed into water which was absorbed freely. The change rules of the moisture content and saturation were analyzed and the prediction formulas for concrete humidity with soak time were found. The results demonstrate that the concrete humidity exhibited a significant increasing trend with increasing soak time. Besides, the lower the strength grades, the smaller the maximum aggregate particle size, the larger the specific surface area, the water absorption rate is faster and the humidity is higher. When the soaking time is 72 h, the concrete saturation of C15, C20 and C30 specimens reaches 96. 88%, 96. 59% and 97. 70%, respectively. With the extension of soaking time, the concrete humidity increases slowly, and the water absorption process of concrete can be approximately divided into linear water absorption, nonlinear water absorption and approximate saturation stages.

Abstract:As a frequently inundated region in Nanjing, Guangzhou Road and its surrounding area were selected as the study site in which a one-dimensional storm flood model was built based on SWMM. The inundation induced by the storm event occurred in July 18^th, 2011 was simulated using the measured rainstorm data. The function relationship between the total cumulative inundation volume and the maximum inundation depth was fitted, and the starting and lasting time of the inundation and the maximum inundation depth were calculated, which were compared to the inundation induced by the design storm with 100-year return period in Nanjing. The results reveal that the fast calculation method for the maximum inundation depth proposed in this paper can dynamically calculate the inundation induced by the storm in July 18^th with high simulation accuracy, which can timely and effectively support flood control and drainage emergency decision-making. Compared with the storm in July 18^th, the maximum inundation depth and the lasting time of inundation remarkably increase under the condition of the design storm with 100-year return period.

Abstract:The improvement of the sill on the recirculation flow and the deflected flow downstream a unilaterally arranged pump-gateway was investigated based on a method combined numerical simulation of Flow-3D with physical model experiments. The effects of the size and location of the sill on the length and width of the recirculation flow and the velocity non-uniformity coefficient were studied, which can provide references for optimal design of the sill. The results show that the sill can suppress the recirculation flow and the deflected flow effectively, resulting in quick diffusion of the unilateral flow into the whole river width. The length and the width of the recirculation zone and the non-uniformity coefficient all decrease with the increase of both the height and adjacent distance of the piers, indicating a good rectification effect. With the increase of the sill width, the above parameters decrease at first and then increase, corresponding to better and non-significant rectification effect respectively. The variation trend of the velocity non-uniformity coefficients for all cases is similar in the flow direction, which increases at first and then decreases.

Abstract:Based on numerical simulation, the flood control safety of the No. 2 ogee spillway tunnel on the left bank of the Xiaolangdi Hydropower Station was analyzed from the aspects of discharge capacity, cross-sectional velocity, tunnel space, piezometric head, cavitation number and jet flow induced scouring. The simulated results were compared with a 1∶40 physical model experiment. Meanwhile, corresponding measures were proposed to solve the common safety problems during the operation of the ogee spillway tunnel. The results show that the simulated results are basically consistent with the experimental results, which indicates that it is feasible to use numerical simulation to analyze the flood control safety for the ogee spillway tunnel.

Abstract:To deepen the understanding for the seepage failure mechanism of earth rock junctions for crossing-dyke sluices, a testing apparatus was designed to accomplish the indoor simulation for the seepage failure process of the junctions between sluice side wall and soil mass. Then, the failure characteristics of contact scouring and its development were analyzed with the clay mass fractions of 4. 6%, 12. 3% and 22. 6%. The effects of soil properties, hydraulic gradient and compactness of the contact zone on seepage failure were studied. The results show that the typical contact scouring process can be divided into three stages, i. e. , stable seepage, piping formation development, and erosion failure. The higher the clay content and compactness, the longer duration will be for stable and failure stages with stronger erosion resistance. There is a significant inverse relationship between erosion and clay mass fraction, hydraulic gradient and compactness. The compactness effect on soil erosion resistance is significant under weak hydraulic gradient. However, with the increase of hydraulic gradient, soil properties play a leading role. At the initial stage of failure, the loss of fine soil particles shows different regularities under the comprehensive effect of soil properties, compactness and hydraulic gradient.

Abstract:In order to study the effects of cement-lime compound modification of expansive soil on water quality, expansive soil samples were taken from the Project of Water Diversion from the Yangtze to Huaihe River which were modified by cement, lime, and cement-lime. The triaxial specimens were fabricated and conditioned for different ages(1 d, 3 d, 7 d, 28 d). The specimens with different curing ages were immersed in water for 1 d, 3 d, 7 d, 28 d, after which the leaching solution was taken and subjected to pH value and Ca⁺ content tests. By comparing the leaching solution testing results and observing the integrity of the specimens after immersion, whether compound modification can reduce the soil impact on water quality was explored. It is found that the pH value and Ca⁺ content of the leaching solution from compound modified soil samples are lower than that of lime modified samples, and the compound modified soil with 28 d curing age has less effect on water quality than that of cement modified soil. In addition, it is suggested a curing age of at least 28 d should be guaranteed in practical engineering, during which rain wash or long-time water soaking should be avoided to ensure the curing quality.

Abstract:The ultimate bearing capacity and failure modes of the maintenance gate slot specimens with different reinforcement ratios were studied through static load tests of three scaled specimens. Based on ABAQUS, numerical simulation of the prototype of the Laxiwa Dam maintenance gate slot was conducted after the numerical model was validated by the experimental results. The failure modes and load transfer mechanism of the maintenance gate slot with different shear span ratios and reinforcement ratios were investigated. The results indicate that the shear capacity of the gate slot is higher than the local compressive bearing capacity if the second-stage concrete is cast without strengthening detailing. Provided that there is sufficient local bearing capacity, the gate slot mainly fails in shear due to the failure of the concrete compression strut if the shear span ratio is greater than 0. 18, otherwise the local sliding damage is dominated. Adding the layers of the horizontal reinforcement along the water flow direction in the maintenance gate slot is able to effectively improve the shear bearing capacity.