Abstract:Spring ecological water requirement for the fishes in the Yellow River Estuary should meet the needs of the habitat and spawning ground of freshwater fishes, channel of migratory fishes, and spawning ground of offshore migratory fishes. According to the living habit of fishes, the time of runoff propagation, the mixing time of fresh water and salt water, and the discharge feature since the operation of the Xiaolangdi Reservoir, key attention should be paid to the water requirement from March to May. A minimum ecological flow discharge of 240 m³/s is needed according to the living habit of fishes and the continuity of the migration channel. A flow discharge pulse with a peak of 890 m³/s, lasting for 8d in the middle stage of April is also needed considering the pulse characteristics in nature period. In this condition, the runoff in spring is 21. 6×10⁸ m³, satisfying the requirement of 21×10⁸ m³ for the low salt spawning condition of offshore migratory fishes. The mean annual spring runoff is 21×10⁸ m³ since the operation of the Xiaolangdi Reservoir. It is of great feasibility to satisfy the fish ecological water requirement by optimizing the annual or the interannual operation modes.

Abstract:Qingsong region in Qingpu District is typical tidal plain river network area. The hydrodynamics of the river network is weak, and the river flow moves back and forth. The problem with the current flowing water scheme of diversion water from the west and the south, drainage to the east and the north was diagnosed based on numerical simulation and field test. The flow rate of water diversion from the west is only 10 to 20 m³/s. The river drainage to north could only depend on pumps and influence very limited river region, leading to rivers with low velocity. Based on the hydrodynamics of high water level in the Wusongjiang River and larger tidal range from the Lanlugang River to the Huangpu River, the optimization flowing water scheme of diversion water from the north, drainage to the east, and naturally diversion and drainage in the southwest was proposed. The result indicates that the hydrodynamics of the optimization flowing water scheme is greatly improved, the flow velocity in the main rivers and in the medium and small rivers increases by 27. 5% and 18. 5% respectively. The flow rate of water diversion is also greatly improved, and the total diversion flow of the Xidayinggang River, Dongdayinggang River, Youdungang River and Xintongbotang River reaches 40 m³/s from the Wusongjiang River. The water quality of the main rivers is obviously improved from grade Ⅴ or worse to grade Ⅳ.

Abstract:According to the current sluice design specifications, five indicators that characterize the safety status of sluice chambers were selected as the research object, and 10 corresponding influencing factors were screened out. Based on Delayed Rejection Adaptive Metropolis(DRAM)algorithm, BP neural network and Garson algorithm, the importance analysis method of the influencing factors for the single and overall safety status of a sluice chamber was constructed. The case study shows that the above method is reasonable and feasible. The research results reveal that for the single safety status index, the water depth in the upstream and downstream, and the wind speed have greater impact on anti-sliding stability and base stress. The seepage slope at the exit section is also influenced by the water depth in the upstream and downstream. The water depth and the wind speed have greater impact on the overall safety status index.

Abstract:Using the standard k-ε turbulence model and the VOF method, numerical simulation of the lateral inlet and outlet, water pipelines and partial upper reservoir of a pumped storage power station was carried out. The effects of division pier layout on the hydraulic characteristics such as the flow rate distribution at the inlet and outlet, the split coefficient of channels, head loss and the flow distribution near the pier head were analyzed under the condition of dead water level. The result shows that, the retro-position of the middle division pier has little influence on the velocity distribution, the split coefficient and the head loss under power generation condition. In the pumping operation mode, the uniformity of velocity and split ratio can be improved, and the head loss can be reduced. However, the improvement is less obvious if the retro-position range is 0. 3 times larger than the initial section of the diffuser. The uniformity of the local velocity near the pier head can be realized if the retro-position of the middle division pier and the side division piers is 0. 44 to 0. 52 times and 0. 1 times the width of the initial section of the diffuser, respectively. The optimization of hydraulic characteristics can be achieved when the retro-position of the middle division pier and the side division piers is 0. 5 times and 0. 1 times the width of the initial section of the diffuser, respectively.

Abstract:In order to explore the influence of the slope of the dam surface with high working heads and large discharge per unit width on the hydraulic characteristics of an integrated energy dissipator, Ahai Hydropower Station was chosen as a prototype based on numerical study, in which a three-dimensional k-ε two-equation turbulence model was used and a gas-liquid two-phase flow VOF computing method was introduced with a geometric reconstruction format to iteratively generate free water surface. Three gradient slope ratios were simulated, including 1∶0. 80, 1∶0. 75 and 1∶0. 65. The results show that, firstly the maximum negative pressure value is located near the lower 1/4 of the first step elevation lobes and increases with the slope. The maximum negative pressure is 61. 02 kPa for the slope of 56. 98°, exceeding 6×9. 81 kPa. Secondly, the minimum cavitation number occurs at the exit point of the wide tail pier water tongue and decreases with the steepness of the slope. The minimum is 0. 358 for the slope of 56. 98°, and the maximum is 0. 381 for the slope of 51. 34°. Thirdly, as the slope of the dam surface becomes gentle, the maximum flow velocity at the bottom of the stilling pool increases, with the highest value for the slop of 51. 34°, which reaches 26. 84 m/s, exceeding 25 m/s and is prone to erosion. The maximum velocity at the bottom of the stilling pool is the smallest, being 24. 00 m/s for the slop of 56. 98°. The maximum flow velocity before the tail of the stilling pool decreases with the increase of the slope. The minimum is 9. 63 m/s for the slope of 56. 98°, and the maximum is 9. 96 m/s for the slope of 51. 34°. Finally, the slope has little effect on the energy dissipation rate of the integrated energy dissipator. The slope increases from 51. 34° to 56. 98°, but the energy dissipation rate only increases by 0. 15%.

Abstract:The unconfined compressive and split tensile tests of plain cement soil and basalt fiber cement soil before and after freeze-thaw cycles were carried out. The effects of freeze-thaw cycles, curing age, water cement ratio and fiber content on the mechanical properties of the two kinds of cement soil were discussed and compared. The results show that the loss rate of freeze-thaw strength of cement soil decreases after adding basalt fibers. The loss rate of freeze-thaw strength of cement soil increases with the increase of water cement ratio and decreases with the increase of age. The relationship between the unconfined compressive strength, the splitting tensile strength of cement soil after freeze-thaw and the number of freeze-thaw cycles can be fitted by hyperbolic curves. The ratio of splitting tensile strength to unconfined compressive strength is between 14% and 17%.

Abstract:In order to improve the measurement efficiency of river ice thickness during the stable freezing period, the ice thickness measurement of the Shisifenzi bend in Inner Mongolia of the Yellow River was carried out by using the airborne radar, and the ice thickness was compared with the measured values of ice ruler. The results show that the thickness of the ice on the concave bank side is in the range of 50~90 cm, which is about 10~30 cm thicker than that on the convex side. The thickness of the ice on both sides of the free flow is consistent, with an average thickness of about 50 cm, and the closer to the free flow, the lesser the thickness of the ice. For the ice measurement effect of airborne radar, the flat seal ice sheet is the best(absolute error less than 5 cm), the vertical freeze-up ice sheet is the second, and the accumulation ice sheet is the worst. The standard deviation of the measured ice thickness between radar and ice ruler is 0. 039 4, and the random uncertainty is 7. 88%, satisfying the requirements of the ice thickness observation specification. The airborne radar can quickly measure the ice thickness in a large scale continuously, which greatly improves the test efficiency of ice thickness and can be applied to ice thickness tests during the stable freezing period of the Yellow River.

Abstract:A finite element numerical model was established to simulate the local scour of a submarine pipeline under steady flow to obtain the bed morphology at different times during the local scour development process. Based on the unsteady Reynolds-average N-S equations and the k-ε standard turbulence model, the Exner equation was solved to simulate the change of seabed. A dynamic mesh technique was used to show the change process of seabed. The equations were discretized by the characteristics method in time and by finite element method in space. The model was verified by the flow around a two-dimensional square bluff body and Mao’s clear water scour test. The results show that the simulation results are in good agreement with the test data, and the model can be used to simulate the local scour of submarine pipelines.

Abstract:Based on the analysis of the restricting and influencing factors for the construction scale and plane layout of the Yuxi Shiplock expansion and reconstruction project, the annual freight volume and the ship throughput were forecasted and the construction scale, the lock position and the general layout of the project were determined. A two-dimensional hydrodynamic model was established to simulate the navigation flow conditions of the approach channel and the entrance area in the upstream of the regulating sluice and the Yuxi Shiplock under various operating conditions. According to the calculation results, the local route alignment of the upstream entrance area and the connecting section is adjusted. Countermeasures reducing the flow velocity and ensuring the navigation safety are proposed, including dredging at the north side of the two curved sections, enlarging the cross-section of the water flow, reducing the flow velocity. The construction scale, lock position and general plane layout of the ship lock determined by comprehensive analysis are well coordinated with many contradictions. The research result shows that the in-situ reconstruction scheme is feasible and the design idea can be referred to similar projects.

Abstract:Model generalization is simple in existing weir stability calculation methods, which cannot accurately reflect the flow field and stress distribution of an irregular barrage. Aiming at the problem, a gas-liquid two-phase flow was introduced to solve the surface flow field and the water pressure of the barrage based on finite element method and ANSYS Workbench software. The calculated results of the flow field were coupled into structural mechanics analysis to complete the stress and deformation analysis of an irregular barrage dam. The results show that the compressive stress can meet the foundation bearing capacity requirements under design flood level and ordinary water level working conditions, and there is no tensile stress inside the barrage dam. The overall deformation distribution of the barrage is reasonable, which can well reflect the discontinuity of the barrage body and the foundation. Therefore, this method can effectively solve the difficulty of stability analysis caused by the complex three-dimensional shape of the barrage and the uneven surface pressure distribution, providing the basis for barrage design.

Abstract:Aiming at the shortcomings of existing cut-off walls with polymer during construction, including limited trench capacity, difficult verticality, poor continuity and compactness, the improvement for the construction equipment and technology was carried out and the effects were inspected. The results show that the application of the electronic level instrument of biaxial measuring column realizes the accurate hole sleeve of the cone head plate. Lengthening the guide rod and changing the fixed cone head into one-time movable cone head can improve the speed and accuracy of hole insertion and can ensure the verticality and continuity of the overlapping hole. The integrated construction technology of lifting and injection can avoid collapse or shrinkage of the slot hole, and the uniformity, continuity and compactness of the wall can be ensured. The improvement of the construction equipment and the technology of super-thin cut-off walls with polymer can ensure the verticality and lap integrity of the wall, improve the working efficiency of the equipment, accelerate the construction progress.

Abstract:In order to improve the construction efficiency and the utilization rate of fine grained tailings, cement of different mass ratios was mixed with fine tailing slurry of which the mass concentration was set to be 40%. Grouting test of geosynthetic tubes was carried out to explore the influence of cement content on the grouting characteristics of geosynthetic tubes. According to the experimental results, the addition of cement as curing agent in the fine tailings mortar can improve the water permeability and sand retention of the geosynthetic tubes. The grouting time and the density of mortar discharging decrease with the increase of the cement content. The quantity of single grouting and single discharge decreases exponentially with the increase of time. The discharge is concentrated in the first two hours, dominated by hydrostatic pressure, and after that, the discharge is dominated by consolidation extrusion due to the dead weight of the fine tailings. The drainage rate, drainage efficiency and sand retention rate increase with the increase of cement content. The drainage efficiency and sand retention rate can be selected as the indexes to evaluate the permeability and sand retention of geosynthetic tubes, and the optimal cement content is determined as 3% after comprehensive consideration of construction efficiency, utilization rate of fine tailings and construction cost.

Abstract:The process of overtopping breach and the numerical simulation of coastal flood evolution in urban interior at home and abroad was summarized. The mechanism model of dike-break was reviewed from three aspects, including the erosion at the bottom of the breach, the widening of the side wall of the breach and the retrogressive erosion of the downstream slope. The advantages, disadvantages and applicability of various flood inundation models and the generalization method of urban buildings were analyzed. Aiming at the shortcomings in the current study, it is necessary to improve the flood model of seawall breaching through physical model tests, strengthen the research of erosion and transportation of sediment in the breach, improve the theory of sediment transport in high-speed flow, optimize the porosity model of urban flood, and fully consider the impact of urban drainage system and vehicles on flood propagation.

Abstract:Characterizing groundwater flow patterns and preferential pathways is basic premise and hot issue for prediction of groundwater flow behavior in fractured media. With the advantage of strong space-time continuity, high spatial and temporal resolution, simple measurements as well as low cost, Distributed Temperature Sensors (DTS) has been applied in heat tracer tests to study groundwater flow and heat transport in fractured media recently. DTS based heat tracer tests have gradually become an important method to identify hydraulically active fractures and to estimate their hydraulic properties, and have provided new insights in characterizing groundwater flow in fractured media. The principles of DTS, the methods of heat tracer tests based on DTS and their applications in the characterization of groundwater flow in fractured media were introduced and summarized. Various experimental methods, application modes and range of application involving DTS were reviewed. Special attention should be paid to the vertical flow in boreholes, which is a key factor for researchers to focus in the application of DTS. Integration of various DTS based heat test methods and the combination with other tracer methods can be regarded as the research interests in the future. In addition, DTS-based heat tracer test has great potential in understanding of groundwater flow and heat transport process in fractured media, making it a promising application prospect in deep geological engineering activities including high-level radioactive waste geological disposal, exploitation of hot fractured rocks.