Gate Pier Research Articles

Research on the Safety Assessment of Corbel Beams of Reservoir Radial Gates Based on Real States

The radial gate corbel beam is a kind of gate support structure more often used in large and medium-sized reservoirs, but the current corresponding structural design code does not give a review calculation method for it. Because there are obvious differences between a corbel and a corbel beam in structural form and force, if the corbel beam is just simplified in the calculation as a corbel structure, it can easily lead to misjudgment of insufficient bearing capacity. This misjudgment has a significant impact on later safety assessment, danger removal, and reinforcement. Currently, there are limited studies available on the internal stress distribution of the corbel beam. In this study, taking the danger removal and reinforcement of the radial gate beam of a medium reservoir in Beijing as an example, the concrete quality of the dam was tested by the core drilling method, and two safety review methods of the corbel beam for different types of reservoirs were proposed in combination with the Code for Design of Hydraulic Concrete Structures (SL191-2008). Then, three different types of calculation model were established by the method of theoretical mechanics calculation and finite element simulation. Combined with the safety test data, the stress state of the combined stress structure of the corbel beam and gate pier under the real state was analyzed and the safety evaluation was carried out. The calculation results of these two corbel beam safety review methods were respectively reduced by 32% and 47% compared with the current calculation method. Engineering practice has proved the rationality of the two safety evaluation methods proposed in this paper, which can provide a certain reference for similar engineering reinforcement.

Characteristics and Hazards Analysis of Vortex Shedding at the Inverted Siphon Outlet

This paper studies Karman vortex shedding and water-level fluctuation in the inverted siphon structure of the Middle Route of the South-to-North Water Diversion Project (MR-SNWDP) in China. Field investigations and numerical simulations for the inverted siphon outlet were performed to explore the characteristics and hazards of the vortex. Numerical results were compared with measured data to verify the effectiveness and reliability of the model. Based on the model, it is found that the periodic water-level fluctuations caused by the Karman vortex street will not only excite surges to beat the gate but will also induce periodical force on the gate pier. Those will damage the building structure and affect the delivery capacity in the long-term operation. Based on this, countermeasures of altering different pier tail shapes are proposed to control vortex shedding, and the effect is noticeable. The study presents a hydraulic process for the inverted siphon outlet and provides a theoretical reference for water delivery safety of inverted siphons and similar structures in MR-SNWDP.

Impinging pressure and flood discharge atomization in high arch dams with flaring gate piers

This study discusses the effects of geometrical parameters of flaring gate piers, such as contraction ratio, sidewall extension ratio and plunge angle, on the impinging pressure and flood atomization based on hydraulic model tests and atomization simulations. It is found that the impinging pressure decreases and the length of rainstorm increases with the increasing impact collision of aerated jets. Decreasing the plunge angle and increasing the extension length of sidewall for violent collision should be considered in the design stage and protection measures for rainstorms should be taken into account. Reducing the atomization hazard by collision avoidance could be selected in the operational phase on the premise of safety factor of plunge pool. A simplified formula is developed to predict the length of rainstorm as a function of the maximum impinging pressure, for use as a reference in the design and modification of similar projects.

Analysis of deformation characteristics of flood gates of runoff hydropower stations under different operating conditions in case of frequent floods

The safety and reliability of flood gates of runoff hydropower stations in the basin are very important. There is no clear rule on the mechanical causes of flood gate deformation in runoff hydropower stations under frequent floods. Therefore, this paper takes a hydropower station as the research object, adopts the unidirectional fluid-solid coupling method, and investigates the stress displacement of flood gate under typical frequent flood conditions by using ANSYS and Fluent software. The results show that the maximum stress of the flood gate is located at the intersection of the bottom two sides of the gate panel and the gate pier, and the stress meets the stiffness requirement. When the gate is opened, the stress distribution range of the panel is shifted from the top to the bottom, and the stress decreases with the increase of the gate opening degrees. The maximum total displacement is concentrated at the bottom of the central axis in the direction of the panel span, and gradually decreases from the middle of the gate panel to the left and right sides, showing a fan-shaped distribution, and basically symmetrical along the central axis of the panel. The flood gate is mainly deformed along the downstream direction, with obvious depression characteristics.

The City Gate in Ancient Israel and Her Neighbors: The Form, Function, and Symbolism of the Civic Forum in the Southern Levant

The City Gate in Ancient Israel and Her Neighbors: The Form, Function, and Symbolism of the Civic Forum in the Southern Levant

Simulation research on hydraulic characteristics of conical X-shaped flaring gate piers in lock chamber based on CLSVOF method

3-D numerical simulation was carried out for flood discharge and energy dissipation process of conical X-shaped flaring gate piers in a hydropower project by using coupled Level Set and VOF method and RNG k-ε turbulent model. The change laws of flow pattern, water surface profile, velocities and pressures distributions in lock chamber of conical X-shaped flaring gate piers were gained. The results of numerical simulation were compared with the model test data and good agreement was found. The numerical results show that, there are differences on both of water surface profiles in lock chamber. With the increase of discharge, water surface profiles falls at the longitudinal axis and vertical diffusion of ski-jump flows are large on the downstream of flaring gate piers.

Experimental study on broaching self-locking anchor rod with mega prestressing force

In order to solve the problem of applying super-tonnage prestressing force to the gate pier in the process of dam reinforcement, this paper presents a comparative study on the three groups of test specimens of prestressed counterbore self-locking anchor rod and unbonded prestressed anchor cable. T show: (a)both methods satisfy the needs of applying prestress, the experiment conducted on the gate pier that is to be renovated has tested the prestress loss of two schemes and the concrete stress in both free section and anchor section after applying the prestress. The results and counterbore self-locking anchor rod boasts shorter anchorage section and better applicability. (b) the anchorage sections of two schemes generate additional tensile stress, and the maximum additional tensile stress in the anchor rod features 54% less than that of anchor cable, smaller range of additional tensile stress and more reasonable stress state of concrete than that of anchor cable.

EFFECTS OF CONCRETE OVERLAY JOINT CONDITIONS AND STRAIN RATE ON SPLITTING TENSILE PROPERTIES

In Japan, design ground motion has increased due to the frequent occurrence of large earthquakes. To improve seismic performance, dams and spillway gate piers (hereafter, piers) are being reinforced. The methods used to strengthen them include concrete overlay, jacketing, etc. On their boundaries, there are concrete joints. These joints are designed as integrated bodies. However, although no accidents have been reported, the joints may be a weak point. The purpose of this study is to understand the effects of concrete joint condition, assuming strengthening for dams and piers such as concrete overlay and jacketing. Dynamic splitting tensile tests of concrete specimens joining old and new bodies were conducted. In dynamic splitting tensile tests, the experimental parameters are the condition of joint surfaces in terms of strengthening and strain rate for earthquake ground motion. The conditions of joint surfaces are raw concrete surfaces, chipped surfaces, and surfaces with rebar insertion. Three cases of strain rate are considered, including a static case and two dynamic cases (about 1,000 μ/s and 10,000 μ/s). Test results showed all joint conditions caused a decrease in tensile strength. There was the effect of increasing tensile strength due to strain rate, regardless of joint condition. It was shown that concrete joints without adhesives might be weak points in reinforced structures.

Floating Ice Transport Conditions at the Cross-Sections Between Pier Columns in Open Ice-Water Two-Phase Flow Canals

Floating ice is easy to jam at the cross-sections contracted by bridge pier, gate pier, etc., in ice-water two-phase flow canals. To solve the problem, the critical hydraulic conditions of floating ice transport at the cross-sections between pier columns were explored in this study. Based on the generalized physical model of the cross-sections between pier columns of water transfer canals, the movement and transport characteristics of floating ice in front of the pier columns were studied under different hydraulic conditions and ice conditions, and the critical hydraulic conditions necessary for floating ice to pass through the cross-sections between pier columns were analyzed. Moreover, dimensional analysis and regression analysis were carried out in order to establish an empirical equation for calculating the critical water flow Fr (Froude number) for the floating ice to be transported through the cross-sections between pier columns, thus providing a basis for the ice jam risk assessment and hydraulic regulation of ice-water two-phase flow canals, as well as control of the emergent ice drainage of canals during freezing periods.

Experimental study and flow analysis on a new design of water-retaining sluice gate

Abstract As a water-retaining structure, the hydro-automatic flap gate (HFG) has advantages, such as easy operation, simple structure, attractive appearance, cheaper investment, and simple installation and maintenance compared to traditional gates. As such, the flow pattern analysis and flow rate analysis on this hydraulic structure have important engineering significance. In this paper, an experimental study was carried out for testing the water flow during the opening process of a bottom shaft driving flap gate. Three different opening velocities (once in 20 years, once in 50 years, once in 100 years) were selected for obtaining detailed characteristics. Then the space-time change laws of velocity and other hydraulic parameters of gate, gate pier and stilling pool were described. Moreover, the results of the flow regimes under conditions of once in 20 years, once in 50 years, once in 100 years were compared with each other. The findings and conclusions of this paper provide the basis for the project implementation in a sediment-laden river, and provide reference for other similar projects.

Numerical Simulation of Air–Water Two-Phase Flow on Stepped Spillways behind X-Shaped Flaring Gate Piers under Very High Unit Discharge

Stepped spillways are commonly used under relatively low unit discharge, where cavitation pitting can be avoided by self-aerated flow. However, there are several dams in China with stepped spillways in combination with X-shaped flaring gate piers with unit design discharge considerably larger than specified in the available guidelines. Consequently, air–water two-phase flow on stepped spillway behind X-shaped flaring gate piers under very high unit discharge was investigated using Computational Fluid Dynamics (CFD) simulations. The 3-D Reynolds-averaged Navier–Stokes equations were solved, including sub-grid models for air entrainment, density evaluation, and drift-flux, to capture self-aerated free-surface flow over the spillway. The pressure on the vertical step faces was compared with laboratory data. In addition, the air–water two-phase flow characteristics and prototype step failure of the simulated prototype spillway were analyzed based on the numerical results of velocity, pressure, and air concentration. Moreover, an optimized bottom-aeration was further studied. The results reveal that the involved models can predict the air concentration near the steps. The cavitation index at the stepped surface is below the threshold value, and the air concentration is insufficient under high unit discharges. Moreover, with the proposed optimization of the aerator air entrainment can be improved and thereby cavitation erosion risk can be reduced.

Research on the Reasonable Spacing of Post-casting Belt of 100m Long Inverted-T Shape Concrete Structures on Soft Foundation

Setting up post-casting belt is one of the most important measures for temperature control and crack prevention of mass concrete, but current specifications have not given unified and clear rules on the spacing of post-casting belt. In this paper, a 100m long inverted-T shape concrete structure on soft foundation in Yangtze River Delta region is taken as the research object. The temperature and stress field of concrete during construction under different conditions are simulated by finite element method, and bottom plate’s and gate pier’s recommended spacing of post-casting belt is obtained when poured in different seasons. This will be of guiding significance to the construction of such mass concrete structure.

Energy dissipation in a deep tailwater stilling basin with partial flaring gate piers

Flaring gate piers (FGPs) have been used to increase energy dissipation in stilling basins downstream of spillways. For projects with a low water head and large unit discharge together with a deep tailwater level, energy dissipation inside a conventional stilling basin is usually insufficient. This paper proposes a new partial flaring gate pier (partial FGP) scheme to intensify the energy dissipation inside the stilling basin. The results for the no FGP scheme, the conventional FGP scheme, and the partial FGP scheme were compared using a physical model study and numerical simulations. It was found that the partial FGP scheme (the alternation of flaring and no flaring gate piers in chambers) can contain the submerged hydraulic jump and high-speed water jet in the upstream region of the stilling basin. Thus, the water jet from the FGP chamber was forced to laterally diffuse, thereby intensifying the shear friction and turbulent kinetic energy and forming a vertical vortex from the bottom to the surface. Compared with the other two schemes, the flow pattern in the partial FGP scheme was improved significantly with much deeper air entrainment depth inside the stilling basin and much lower turbulent kinetic energy in the outgoing flow. The mean velocity of the outgoing flow also decreased by more than 20%. The common problems of secondary hydraulic jump outside the stilling basin were eliminated.

Analysis for the Vibration Mechanism of the Spillway Guide Wall Considering the Associated-Forced Coupled Vibration

During the flood discharge in large-scale hydraulic engineering projects, intense flow-induced vibrations may occur in hydraulic gates, gate piers, spillway guide walls, etc. Furthermore, the vibration mechanism is complicated. For the spillway guide wall, existing studies on the vibration mechanism usually focus on the vibrations caused by flow excitations, without considering the influence of dam vibration. According to prototype tests, the vibrations of the spillway guide wall and the dam show synchronization. Thus, this paper presents a new vibration mechanism of associated-forced coupled vibration (AFCV) for the spillway guide wall to investigate the dynamic responses and reveal coupled vibrational properties and vibrational correlations. Different from conventional flow-induced vibration theory, this paper considers the spillway guide wall as a lightweight accessory structure connected to a large-scale primary structure. A corresponding simplified theoretical model for the AFCV system is established, with theoretical derivations given. Then, several vibrational signals measured in different structures in prototype tests are handled by the cross-wavelet transform (XWS) to reveal the vibrational correlation between the spillway guide wall and the dam. Afterwards, mutual analyses of numeral simulation, theoretical derivation, and prototype data are employed to clarify the vibration mechanism of a spillway guide wall. The proposed mechanism can give more reasonable and accurate results regarding the dynamic response and amplitude coefficient of the guide wall. Moreover, by changing the parameters in the theoretical model through practical measures, the proposed vibration mechanism can provide benefits to vibration control and structural design.

Artificial aeration of stepped spillways by crest piers and flares for the mitigation of cavitation damage

Stepped spillways are one of the oldest spillway designs dating back to 500 B.C. With technical advances in Roller Compacted Concrete (RCC) construction, the stepped spillway has become increasingly popular over recent decades. However, the use of this spillway is limited to a maximum safe unit discharge of 25 m2/s due to the risk of cavitation. In order to increase the discharge capacity on stepped spillways, various crest pier designs were introduced for flow aeration, thereby reducing the risk of cavitation damage. These pier designs were investigated on two physical models, constructed on a scale of 1:15 and 1:50, both with a standard ogee crest profile which transit to a stepped spillway chute. Air concentration was recorded along the pseudo-bottom, while pressures were measured at the step riser. The results of the 1:15 scale model indicated that the implementation of a short bullnose pier increased the safe unit discharge capacity to 30 rm/s. The innovative Flaring Gate Pier design, which was adapted on existing spillways in China, with reported design prototype unit discharges exceeding 200 m2/s, was investigated on the 1:50 scale model. Based on the experimental results of the current study, the safe unit discharge capacity (i.e. a discharge satisfying the relevant criteria defined for this study) was increased to 50 m2/s with an X-shape Flare Gate Pier (FGP) on the spillway crest.

Experimental Study on Microscopic Performance of Underwater Concrete of a Sluice

Zaohe Lock was built in the 1950s and has a long running time. The bottom plate, gate pier and apron (covered) parts of the gate were sampled this time, and concrete samples were tested for related performances at the same time, including microscopic pore structure, micromorphology and chemical composition. The results of this experiment will help us to understand the changes in physical and mechanical properties of underwater concrete and its durability changes, revealing the macro and microscopic performance evolution mechanisms of concrete materials, and providing technical reference for the durability design of related hydraulic structures.

Effect of Flaring Gate Piers on Discharge Coefficient for Finite Crest-Length Weirs

The use of flaring gate piers (FGPs) along with finite crest-length weirs changes the shape of plunging jets and increases the efficiency of energy dissipation in some projects; however, the FGPs may affect the discharge capacity. In this study, the flow pattern and discharge coefficient were experimentally investigated under different conditions by varying the weir lengths Lw, contraction ratio β, contraction angle θ, and water heads H. A comparative analysis of the weirs with and without FGPs was performed. For the finite crest-length weirs with FGPs, the water-surface profiles in the flow channel were backwater curves. Moreover, the plunging jets leaving the weir became narrower and then subsequently diffused largely in the transverse and longitudinal directions in air. The discharge coefficients of the weirs with FGPs were approximately equal for various weir lengths. Moreover, following the earlier studies on traditional finite crest-length weirs, a discharge-coefficient equation was developed for the weir with an FGP in this study. The results showed that in the weirs with FGPs, the discharge coefficients clearly increased with the increase in the contraction ratio and water head, but the changes in their values along with the contraction angle were neglected.

A Topology-alterative Algorithm for Transient Dynamic Hydraulic Response Investigation

In this paper, a hexahedra-based topology-alterative algorithm is proposed to simulate dynamic boundary issues of the gate opening motions in water conservancy projects. The algorithm, which cooperates with the two-phase, incompressible solver of OpenFOAM platform, enables researchers to investigate transient hydraulic characteristic variations comprehensively. Two benchmark experiments were performed to validate the numerical results under the working conditions of moving sluice gates and unsteady weir head. The time history response of water level and pressure on specified monitoring points, flow pattern scenario near moving gate, furthermore, the development of antisymmetric-revolving vertical vortices around gate piers were recorded to assess the accuracy of the proposed model. The cross-contrasting results show that the relative error of weir flow time is less than 5.00 %. Moreover, good agreement has been obtained about time history curves of free surface elevation and pressure between numerical and experiment solutions. The vivid flow pattern shows the simulating capability of the current model and indicates an inspiring way to numerically investigate generation mechanism of vertical vortex inside gate grooves. The proposed algorithm is believed to be a useful utility on the further investigation on flow variation in real hydraulic engineering applications, such as improvement of semi-empirical discharge formulas, reduction of cavitation damage, elimination of pipe hammer pressure even spectral analysis of sluice gates with a fluid structure interaction interface.

3D numerical simulation of flow field with incompletely flaring gate pier in large unit discharge and deep tail water project

Limited by large unit discharge above the overflow weir and deep tail water inside the stilling basin, the incoming flow inside stilling basin is seriously short of enough energy dissipation and outgoing flow still carries much energy with large velocity, bound to result in secondary hydraulic jump outside stilling basin and scour downstream river bed. Based on the RNG k-ε turbulence model and the VOF method, this paper comparatively studies flow field between the conventional flat gate pier program and the incompletely flaring gate pier program to reveal energy dissipation mechanism of incomplete flaring gate pier. Results show that incompletely flaring gate pier can greatly promote the longitudinally stretched water jet to laterally diffuse and collide in the upstream region of stilling basin due to velocity gradients between adjacent inflow from each chamber through shrinking partial overflow flow chamber weir chamber, which would lead to large scale vertical axis vortex from the bottom to the surface and enhance mutual shear turbulence dissipation. This would significantly increase energy dissipation inside stilling basin to reduce outgoing velocity and totally solve the common hydraulic problems in large unit discharge and deep tail water projects.

New insights into the spatial variability of biofilm communities and potentially negative bacterial groups in hydraulic concrete structures

The composition and distribution characteristics of bacterial communities in biofilms attached to hydraulic concrete structure (HCS) surfaces were investigated for the first time in four reservoirs in the middle and lower reaches of the Yangtze River Basin using 16S rRNA Miseq sequencing. High microbial diversity was found in HCS biofilms, and notable differences were observed in different types of HCS. Proteobacteria, Cyanobacteria and Chloroflexi were the predominant phyla, with respective relative abundances of 35.3%, 25.4% and 13.0%. The three most abundant genera were Leptolyngbya, Anaerolineaceae and Polynucleobacter. The phyla Beta-proteobacteria and Firmicutes and genus Lyngbya were predominant in CGP, whereas the phyla Cyanobacteria and Chloroflexi and genera Leptolyngbya, Anaerolinea and Polynucleobacter survived better in land walls and bank slopes. Dissolved oxygen, ammonia nitrogen and temperature were characterized as the main factors driving the bacterial community composition. The most abundant groups of metabolic functions were also identified as ammonia oxidizers, sulphate reducers, and dehalogenators. Additionally, functional groups related to biocorrosion were found to account for the largest proportion (14.0% of total sequences) in gate piers, followed by those in land walls (11.5%) and bank slopes (10.2%). Concrete gate piers were at the greatest risk of biocorrosion with the most abundant negative bacterial groups, especially for sulphate reducers. Thus, it should be paid high attention to the biocorrosion prevention of concrete gate piers. Overall, this study contributed to the optimization of microbial control and the improvement of the safety management for water conservation structures.