Abstract:The working mechanism, technical equipment and development process of existing leakage detection methods for earth-rockfill dam leakage were reviewed. The applicable scenarios, advantages and limitations of these technologies were summarized and compared. It is pointed out that the rapid inspection and efficient disposal of leakage danger in flood season is a weak link in the safety guarantee of earth-rockfill dams. The construction of complete equipment system of rapid inspection, accurate positioning and efficient disposal is a direction need to be tackled at present. The establishment of automatic monitoring system and early warning system with space-time continuity is the long-term goal to ensure the long-term and safe service of earth-rockfill dams.

Abstract:Since the safety, durability and adaptability to environment of roller compacted concrete (RCC) dams are related to the safe operation, and especially the interlayer bonding quality can directly affect the seepage resistance and the interlayer anti-sliding stability, the safety status of RCC dams were overall elaborated. Concentrated on the mechanical behavior and the service performance of RCC dams, advances in the aspects of bonding performance, mechanical characteristics, temperature change effect, seepage analysis, safety monitoring and comprehensive evaluation were reviewed. It should be highlighted the basic theory and methodology of the interactive evolution mechanism of RCC materials and structures, the deterioration mechanism of RCC dam performance during long-term operation, corresponding identification and early warning methodologies, and intervention technologies as well should be further investigated in the future.

Abstract:To improve the prediction accuracy of concrete dam deformation, a Long Short-Term Memory(LSTM) network-based concrete dam deformation prediction model is proposed, which hasthe merits of excellent nonlinear data mining ability and the long and short-term prediction performance of time series.Example analysis shows that, compared with the commonlyused stepwise regression and multiple regression methods, the LSTM network-based deformation prediction model can effectively mine the complex nonlinear relationship between dam deformation and influencing factors. The modeling and predicting accuracy of the model can be significantly improved, providinga new method for dam deformation prediction.

Abstract:Accelerated dissolution tests were conducted for concrete specimens with pouring layer interface using nitric acid solution with the concentration of 0.5 mol/L. The evolution laws of three leaching evaluation indexes, which were the splitting tensile strength, leaching depth and cumulative relative leached calcium, and the effects of interval time and layer roughening on the leaching process were studied. Two prediction models were then established for the splitting tensile strength of the layer interface. The research results show that the splitting tensile strength has linear relationships with the square root of leaching duration and the cumulative relative leached calcium. The interval time and layer roughening mainly affect the initial value of strength and have little effect on the linear slopes. The leaching degree of layer interface increases with the interval time, in which the leaching depth of layer interface increases by 15% when the interval time comes up to 24 h. The reinforcement effect of layer roughening on leaching resistance decreases with the interval time, and 6 h is the optimum interval time. When the interval time is less than 12 h, the splitting tensile strength of layer interface decreases fast, and the decrease rate is 14.6% within 12 h, which can reduce the leaching resistance service life of the concrete layer interface by 61%.

Abstract:In response to the increasingly serious urban waterlogging problem in recent years, the MIKE FLOOD model was used to simulate the flooding and inundation status of the Yuehu New District in Yingtan City when it encountered rainfall during the return periods of 1.a, 3.a, 5.a, 10.a and 20.a. The complete process of the formation and recovery of urban waterlogging under different return periods of rainfall was investigated. According to the simulation results, the number of submerged grids in the study area after rainfall in each return period were counted. Based on the system performance analysis, the waterlogging elasticity of the Yuehu New District was studied, and the research area’s defense and recovery capabilities against rainfall disasters in each return period were further analyzed. The results show that under different return periods of rainfall, the accumulated waterlogging area in the study area basically reaches the maximum at about 65 minutes. The drainage system of the study area is more sensitive to rainfall during the low return period from 1a to 3a. The lower the return period of rainfall, the faster and better the recovery level of the system performance.

Abstract:Two-stage Stochastic Programming (TSP) was used to optimize the allocation of water resources between cities in Heilongjiang Province with different inflow and risk levels, and the problems of optimal allocation and uncertainty in water resources system were solved. Conditional value at risk (CVaR) was used to measure the risks in water resources system to avoid the risks and maximize the economic benefits. When risk preference is not taken into account, the total revenue of Heilongjiang under the low, medium and high scenarios are (524.535~793.332) billion yuan, (861.664~962.580) billion yuan and 1.53.050 billion yuan respectively. When the risk preference value is from 0.1 to 0.9, the amount of water allocated by each city’s tertiary industries decreases with the increase of risk preference, and the administrators can choose appropriate water allocation schemes according to the degree of risk aversion of different industries. This study provides references for scientific allocation of urban water resources management.

Abstract:The siphon formation process with different section forms was simulated by using the VOF model considering gas compressibility, which was verified by an experiment. The effect of section forms on the hydraulic characteristics of the siphon outlet was analyzed from the three aspects of velocity distribution, hydraulic loss and siphon formation time. The results show that the results between simulation and experiment are in good agreement. The section forms have great influence on the hydraulic characteristics of the siphon outlet passage. Rationally designed gradual change section can uniformly distribute the velocity and pressure distribution inside the passage, but it can increase the head loss of the system. Circular pipes have the least hydraulic loss, but the exhaust capacity is weaker than that of square pipes.

Abstract:In the numerical simulation of rainfall intensity for flood discharge atomization, mass production of water droplets needs to be generated during the solution of random droplets splashing mathematical model, which leads to the problem of low computational efficiency. Based on the academic ideas of particle motion optimization calculation methods, such as graded droplet spectrum, representative oil droplet and particle group, the concept of graded droplets was first proposed, and a graded random splashing droplets mathematical model was established. The effectiveness of the proposed model was verified by comparing with an example with an analytical solution. The comparison results show that the solution precision of the graded random droplets splashing mathematical model with 10,000 water droplets is very close to that of the random droplets splashing mathematical model with 1 million water droplets. It is shown that the graded random droplets splashing mathematical model is more advantages in calculation than the random droplets splashing mathematical model.

Abstract:To improve the prediction accuracy of concrete dam deformation monitoring data, a long and short-term memory network (LSTM) prediction model was constructed based on integrated empirical mode decomposition (EEMD) and sample entropy reconstruction (SE). In this model, EEMD is firstly used to decompose the original data sequence, and the sample entropy of each component sequence is then calculated. The sample entropy of the original sequence is used as the reference for reconstruction, and then the LSTM model is established to predict the reconstructed sequences. Finally, the predicted values are superimposed to obtain the final prediction result. Taking a concrete arch dam as an example, the prediction results of the EEMD-SE-LSTM model were compared with those of EMD-LSTM, LSTM and SVM models. The results show that the EEMD-SE-LSTM model has higher prediction accuracy and better feasibility and superiority in the prediction of concrete dam deformation.

Abstract:The evaluation system and model of agricultural resilience index in Henan Province were constructed based on the Notre Dame Global Adaptation Index (ND-GAIN) model developed by University of Notre Dame, and the entropy weight method was used to determine the weight of each factor. The environment of agricultural resilience in Henan from the aspects of vulnerability and preparation degree was investigated respectively. The evolution, spatial distribution and main influencing factors of agricultural resilience in 18 cities of Henan Province from 2010 to 2018 was discussed, and the spatial map of the resilience grades was drawn by ArcGIS software. The results show that the general agricultural resilience of Henan Province is on the rise but however, except for Zhengzhou, Luoyang and Nanyang, the overall level of agricultural resilience is still low with significant regional differences. The overall trend is high in the west, low in the southeast and weaker in the north and south, among which Zhengzhou and Hebi has the highest and lowest comprehensive score respectively. The difference in vulnerability index is relatively small, and the difference in readiness index is relatively large, which is the main reason for the obvious difference of agricultural disaster resistance.

Abstract:The hydrodynamic numerical model of the Yihe River was established based on MIKE 11 software, and the model was verified by using the measured data. Six rubber dams along the Yihe River and the Benghe River were selected, among which the discharge process of each single rubber dam was calculated first and then the joint application of rubber dams was studied according to the scheduling principle of the dam group. The results show that in the condition of 4 hours collapsing time for all the dams, the peak discharge downstream the Linyi section is 1.427 m3/s and the peak discharge of the Xiaobudong rubber dam is 1.414 m3/s. The increase of discharge is less than 1% after the operation of rubber dam group. The scheme of dam collapse is put forward under the flood condition in 2022, in which the flood forecasting time upstream the Linyi section is longer than 8.95 hours. The proposed dam collapse scheme can store the water in advance and the peak flow discharge is not increased.

Abstract:Since the deformation of embankment caused by shield construction of large-scale tunnel passing through embankment would cause anti-seepage body destruction, the Yangtze River embankment should be reinforced for seepage prevention. Taking the actual crossing river embankment of Sanchahe River section in Nanjing as an example, in which the tunnel Line N of Weisan Road crosses the Yangtze River. For the situation of scattered seepage danger in flood season, the risk elimination and anti-seepage reinforcement technology was investigated and applied. Based on field tests, a wall forming scheme and corresponding treatment technology was proposed, in which cement clay slurry was firstly poured with a solidification period of 7 to 15 days, and then the high-pressure jet grouting pile with double pipe method after the leading hole was adopted. The danger risk of the embankment was successfully eliminated. After completion of the project, the embankment has stood up to the exceeding history flood with 10.39 m water level of the Yangtze River in 2020, and the anti-seepage performance of the embankment meets the functional requirements.

Abstract:To explore the response of a double-row steel sheet pile cofferdam under the condition of different wave modes, the effects of near breaking wave and standing wave on steel sheet piles was compared through flume test using optical fiber testing technology, and the mechanism of wave load caused by standing wave and near breaking wave was analyzed. It is found that the main unfavorable effect of standing waves on the double-row steel sheet pile cofferdam is the scouring of the seaside steel sheet piles caused by the reflected waves. The main unfavorable effect of the breaking wave on the double-row steel sheet pile cofferdam is the huge crushing energy and rapid impact during wave breaking. The deformation of the steel sheet pile may cause accidents such as leakage of the joint and soil erosion of the infilled sands.

Abstract:The Nanxian West-to-East Water Diversion Project and the Huahong Canal Connection Project were selected as typical cases, and the planned water system in the Dongting Lake area was optimized and evaluated based on connectivity indicators. The results show that the connectivity of the water system structure has declined under the planning conditions, indicating much room for optimization. Under the optimized conditions, the flow discharge of the west and middle branches of the Ouchi River in the Nanxian West-to-East Water Transfer Project increases up to 9.3 m3/s and 5.3 m3/s, and the hydrodynamic conditions are significantly improved. The discharge distribution coefficient at the outlet node of the optimized corridor is increased by 16.7%, effectively increasing the water delivery volume of the Zhongjiazui irrigated area. After the optimization, the water exchange cycle for increasing the storage capacity of the south and north lake group of the Huahong Canal Connection Project is reduced to 5 and 8 days, respectively, and correspondingly the water exchange efficiency is increased by 55.71% and 12.26%, respectively.

Abstract:Based on the hydrogeological data of an island, the hydrogeological conditions of the study area were generalized, and the corresponding two-dimensional numerical model was established by using Visual MODFLOW. The formation and water storage capacity variation of the lens was simulated by changing the coverage area of the impervious surface. The simulation results show that the maximum thickness of the initial island freshwater lens is 15.6 m. After configuration of the impermeable surface, the freshwater lens is stable again after 15 years. The outline of the lens with impervious surface is concave inward, and the maximum thickness is reduced to 14.6.m, and the underground fresh water storage of the island is reduced by 20.23%. Sensitivity analysis of the four influencing factors of the fresh water lens shows that the aquifer specific yield has the greatest impact on the underground freshwater storage, and then follows the impact of precipitation infiltration intensity, permeability coefficient and impervious surface coverage.