Concrete Spillway Research Articles

Comparing labyrinth and ogee spillways at high hydraulic heads – a case study in Zambia

A new over-the-dam spillway and 3 m dam raising were selected as the preferred option for resolving matters in the interest of safety for an existing dam in Zambia. The cost of supplying concrete at the dam site had the greatest effect on overall project capital costs, and thus optimising the size of the concrete spillway was critical. Both ogee and labyrinth weir designs were developed for a hydraulic head of 5 m in the Safety Check Flood. The ogee shape design was developed to achieve high efficiency and required a weir width of 81 m. For labyrinth weirs, a limiting factor to the allowable head is the ratio between the water head and weir height above its foundation apron. Using published state-of-the-art research, 60 labyrinth weir configurations were tested, with varying angles, leg lengths and number of cycles. The optimal labyrinth configuration was chosen as the one with the minimum overall spillway width 64 m, and volume of concrete. This configuration provided a 23% potential reduction in concrete volume compared to the ogee. The labyrinth design was taken forward for computational fluid dynamic modelling to prove the concept and for further development into a detailed design.

КОМБІНОВАНІ ВОДОПРОПУСКНІ СПОРУДИ ТУНЕЛЬНОГО ТИПУ ДЛЯ ДОРОЖНЬОГО ГОСПОДАРСТВА

The paper consist developed the method of arranging combined structures used as foundations for fragments of regional and local roads over small streams and spillways, which combine the functions of standard monolithic slab-type bridge structures and floodgate box structures. The proposed method is a more reliable alternative to modern standard solutions in the form of prefabricated concrete spillways or non-pressure pipes of a round cross section, which are installed over natural and artificial barriers ofshort length. In addition, the proposed constructive solution can have a dual use –as a floodgatein normal mode and a temporary shelter (reinforced concrete dugout) for the civilian population at the time of the air raid. Have been detailed described the proposed design solution, have been developed a finite element model of the stress-strain state of a structure, taking into account soil conditions under the action of a complex of loads, including temporary effects from wheeled vehicles. Have been localized the sections of the structures where the largest tension. Have been proposed a rational variant of their reinforcement. Have been confirmed the reliability and effectiveness of the proposed design solutions in the process of analyzing the results of finite element modeling.Have been generalized practical experience in the design and construction of a combined tunnel-type structure in the Dzhugastra village, Kryzhopilskyj district, Vinnytsia region. Have been described the technological sequence of performing construction and installation works on the installation of a structure according to the methodology proposed by the authors of the article

Assessment of the Breaching Event, Breach Parameters and Failure Mechanisms of the Spillway Collapse in the Swa Dam, Myanmar

The spillway of the Swa earthen dam, constructed in Yedashe Township, Bago Region, Myanmar, collapsed suddenly on 29 August 2018 and resulted in a huge flood to downstream areas causing fatalities and the displacement of thousands of localities. This study aimed to assess the spillway breaching process in terms of the breaching parameters such as the average breach width, failure time and peak outflow, and failure mechanisms. We analyzed the event from the changes in the study site before and after the event and used water discharge conditions from satellite data and water level records during the event. We compared the breaching parameters using empirical equations from past failed events with tested scenarios for failure mechanisms, such as overtopping and piping. According to satellite data, 97% of the storage from the reservoir was discharged, and the peak breach outflow rate was 7643 m3/s calculated from the water level records. The selected empirical formulas were applied, and the estimated average breach widths, failure times and peak discharge from the formulas were larger in overtopping and nearer in piping than that of the observed data for the Swa Dam. Thus, a concrete spillway might impact the erodibility rate of breaching compared with concrete-faced and earthen dam types.

Brine seepage tracing in a damaged dam slope using elapsed-time electrical resistivity tomography

The electrical resistivity tomography technique is a geophysical inspection method widely used for several investigations, such as mining exploration, fault localization, groundwater flow, geological exploration, and pollution zones. Infusing brine into substructure can increase conductivity and becomes a useful medium to trace the path of the seepage flowing in rockfill dams. In this article, an elapsed-time electrical resistivity tomography technique was developed to monitor the potential seepage in the damaged dam slopes nearby a concrete spillway. Tracing the downhole brine seepage could effectively identify the possible direction and path of the seepage flowing through the rockfill dam mass in a few hours. The spatial distribution variations of electrical resistivity tomography images can also provide information about the potential sliding surface and the accumulation zones of the seepage in the downstream side slope of the dam.

A cascading risk model for the failure of the concrete spillway of the Toddbrook dam, England during the August 2019 flooding

Dam break is considered as a major catastrophe with significant negative economic, social, and environmental consequences, and thus must be prevented at any cost. Here, we report and analyze a near-miss dam break incident in Toddbrook dam, England during the August 2019 flooding, where the spillway of the dam failed putting the entire dam at the risk of failure. A combination of field surveys, desk studies and numerical modelling is applied to analyze the incident and to develop a cascading risk model for the first time. Our hydraulic modelling showed that the spillway was under fast-flowing water having a speed of up to 15.0 m/s. Such a high-speed flow played a major role in the failure of the spillway through facilitating water injection beneath the spillway slabs. The spillway suffered from poor maintenance and was densely vegetated, which most likely undermined the foundation. The spillway was poorly designed as the concrete slabs were relatively thin and unreinforced, the profile of the spillway was not fit for purpose, and the spillway lacked a stilling basin. Due to rapid drawdown, a landslide was generated on the upstream slope of the dam, which was reconstructed through our geotechnical modelling, indicating that a slower pace must have been taken during the process of emptying the reservoir. We developed a cascading risk model which begins with three primary causes of insufficient maintenance, design shortcomings, and the torrential rainfall leading to flooding. Our risk model, which is among the first of its type, would help preventing future dam failures.

Ground penetrating radar inspection of a large concrete spillway: A case-study using SFCW GPR at a hydroelectric dam

Hydroelectric dams are subject to aging and degradation. The concrete structure under investigation here had visible signs of spalling, cracking, and erosion, but it was unclear how damaged the spillway was below the surface. The asset owners wanted to identify delamination and voids 60 cm or larger so they could mitigate the effects. While most ground penetrating radar (GPR) inspections conducted on dams have been completedusing low frequency ranges between 16 MHz and 500 MHz, these frequencies may overlook small, but critical defects. Our study is the first to use a small hand-held sized stepped frequency continuous wave (SFCW) GPR to acquire information at frequencies ranging up to 4 GHz to evaluate its effectiveness on such a large asset. The two main questions we aimed to answer are: (1) how will a small GPR unit perform on a large, irregular concrete surface, and (2) could the higher frequencies provide more detailed images of small cracks and defects. The study provided useful results in real-time which supported a repair and refurbishment program. The high frequency system allowed for detailed visualization and measurement of reflections events consistent with expectations for delamination and voids. The investigation also identified other non-critical defects that can be targeted for ongoing monitoring programs.

ПОВЫШЕНИЕ ЭФФЕКТИВНОСТИ ГАШЕНИЯ ЭНЕРГИИ ПОТОКА В НИЖНЕМ БЬЕФЕ

The present study assesses the efficiency of using artificial roughness as a flow energy dissipater on the spillway of a low-head concrete spillway. A comparative analysis of the effect of different types of roughness elements in the downstream is presented. Separately, the elements of resistance in the form of bottom ribs lying horizontally at the bottom of the waterfall, as well as vertically standing elements of resistance (cubes, cylinders, concrete blocks, hemispheres) are considered. The influence of the shape of the elements, their location and their distribution density per unit area is evaluated. Among the ribbed elements of roughness studied, the most promising is the double zigzag against the current. Among the vertically standing elements, it is advisable to give preference to elements with sharp edges (cubes, blocks, plates). Most of the works devoted to the study of artifi cial roughness is based on experiments conducted in natural or artifi cial channels with relatively small slopes compared to the spillway face of practical profi le spillways, as well as steeply falling sections of fast currents with slopes of i > 0.3. An assessment of the effi ciency of the bottom ribbed elements on the model of a low- and medium-pressure concrete dam is proposed to identify the most effective structures in relation to the resistance elements often used in practice at fast currents.

Giluyskaya Hydropower – new approach to project development

Multivariate water-power calculations were carried out and the main parameters of the reservoired Gilyuyskaya HPP were justified. The Gilyuy river is located in the Amur Region of the Far Eastern Federal District and is a right tributary of the Zeya River. The mouth of the Gilyuy river is located above the power site of Zeyskaya HPP. Based on the water-power calculations, it was found that the most efficient way is to use live storage capacity of 3.13 km3 and the turbine flow rate of HPP equal to 268 m3/s. The installed power capacity of Giluyskaya HPP is justified on the basis of maximizing the net present value and is assumed to be 213 MW. Hydropower has three hydraulic units with radial-axial turbine RO115with impeller diameter of 3.35 m and synchronous speed of 214.3rpm.The high-head water power development includes as follows: a concrete gravity dam, a concrete spillway dam with nappe-shaped profile, a concrete power dam with three water inlets and three steel pipelines with a diameter of 4 m, as well as HPP building. The HPP building is 48.68 m long and consists of three hydropower units with a width of 16.23 m. The length of the tent of HPP building along the flowstream is 18.5 m. The assembly area is 24.34 m long.

Socio-ecological consequences during the construction of a multistage system of flood control facilities on side tributaries

A method of protecting territories in a river basin during flash floods by creating a multi-stage system of intercepting flood control systems with temporarily filled reservoirs, with a phased construction of waterworks on side tributaries, including secondary ones. Using the computer programs developed by the authors, the operating modes of the hydroelectric system were simulated for a possible variant of placing their sections on the lateral tributary of the river: in the lower reaches- a traditional hydro system with an earth dam and a concrete spillway, including bottom holes and a surface spillway; upstream- an additional hydro system with a filtering dam made of gabion masonry, into which the missing accumulating volume is redistributed. The calculation of the social effect resulting from the considered method of protection by assessing the reduction of economic damage for settlements located in the downstream of the main flood control hydroelectric complex with participation in the cutoff of the flood peak of an additional temporarily filled reservoir located upstream of the river is performed.

Supports for Repair Gates at the Lower Bureya Hydroelectric Power Plant

The monolithic concrete abutments as supports for the repair gate made by underwater concreting at a depth of up to 21 m in a permanent formwork fixed to the concrete spillway structures are described.

Uplift Pressures below Spillway Chute Slabs at Unvented Open Offset Joints

The catastrophic failure of the spillway chute at Oroville Dam in February 2017 raised concerns throughout the water resources industry regarding design, construction, and maintenance practices for concrete spillway chutes, especially joints and cracks that could allow penetration of high-pressure water into a chute foundation. The independent forensic team investigation found that hydraulic jacking was the most likely cause of the initial chute slab failure, highlighting a need for better analysis of the hydraulic jacking potential of existing spillways and more resilient designs for spillways that operate under high-velocity flow conditions. This paper reviews the Oroville Dam event and findings and previous laboratory testing performed to evaluate uplift pressures and flow transmitted through spillway joints. A reanalysis of previous studies was used to develop relations between chute velocity, joint geometry, and uplift pressure transmitted into a joint. Uplift pressure head in these relations is expressed in a dimensionless manner, either as a percentage of the velocity head in the boundary layer at midheight of the offset into the flow, or as a percentage of the channel-average velocity head. The first approach is potentially more useful for prototype applications, but the second method provides the best fit to the available experimental data. Additional research is still needed to quantify rates of flow through open joints, confirm relations between uplift pressure and boundary layer velocities, and evaluate the effects of aerated flow.

Measurement of Abrasion on Concrete Surfaces with 3D Scanning Technology

AbstractHydraulic structures play an important role in regulation and transport of water in reservoirs and open channels. Examples of such structures include concrete spillways, stilling basins, fl...

Slope Stability of Darbendikhan Dam Site and Near Surroundings. A Reconnaissance Study, Kurdistan Region, NE Iraq

Darbendikhan Dam is constructed on the Sirwan (Diyala) River during 1955- 1961. The dam is of earth fill type with concrete spill ways and gates for electric power generation. The dam axis is almost E – W with both left and right abutments being constructed within the Gercus Formation, which consists of red clastics with more claystones. The Gercus Formation is overlain by the Pila Spi Formation that consists of hard to very hard, well bedded carbonates. The Pila Spi Formation is overlain by the Fatha Formation that consists of thick reddish brown claystones alternated with thin gypsum and limestone beds. Both Gercus and Fatha formations form steep to very steep slopes on upstream and downstream, respectively. All the slopes on the dam site and near surroundings suffer from different types of mass movements with different sizes. Some of them are old and dormant; others are recent and active exhibiting geological hazards, which may cause large loss of human life and the existing properties and infrastructure. We studied the slopes using different types of satellite images with different resolutions and conducted field trips to the dam site to collect data. We recommended some precautions to make the slopes more stable.

Gatun Dam—megastructure of the Panama Canal

Abstract The kingpin structure of the American scheme to construct a ship canal across Panama in 1907–1914 was an earthen dam of unprecedented scale and scope at Gatun, to retain the aggregate flow of the Chagres River and its principal tributaries. Upon this structure alone, the entire plan rested, because it created the man-made lake rising 85 ft (25.9 m) above sea level, which allowed ships to cross the 550 ft (167.6 m) continental divide between the Atlantic and Pacific Oceans. Everything about Gatun Dam was enormous. Its dimensions were without precedent: a crest length of 8,200 ft (2,500 m) and a maximum width of 2,300 ft (701 m). With a height of 105 ft (32 m) above sea level, it stored sufficient water to maintain an operating pool covering 164 mi2 (425 km2). At its center was the most critical structure, a mass concrete spillway capable of passing flood flows of the unpredictable Chagres River. The biggest problem with the site was the underlying geology, which included two deepley incised paleo-channels. The massive embankments were placed over these paleo-channels, which were up to 258 ft (78.6 m) deep. The channel infill of the upper 50 ft (15.2 m) was of relatively low permeability, mostly sandy silts and clay. There were more pervious sands and gravel lying beneath these, which allowed deep seepage cutoffs to be precluded.

Effect of water infiltration through concrete block spillways on the slope stability of earth overflow dams

Using wedge-shaped concrete blocks (WSCB) to protect earth dams against overtopping has received much attention in recent years. The aim of this study is to assess the pattern of the infiltrated flow through the WSCBs system into the downstream shell of the earth dam. Moreover, its effects on the downstream slope stability are investigated using the finite-element analysis. A typical zoned earth overflow dam with the WSCB spillway is modelled. For this case study, the effects of depth and duration of overtopping as well as the permeability coefficient of the shell materials on the water infiltration pattern and the downstream safety factor are studied. The results show that if the permeability coefficient of shell materials is more than 10−3 cm/s, even for overflow with shallow depths, the infiltration rate and the extent of the saturated region will rapidly increase. Consequently, the safety factors will significantly decrease for such cases. However, if the materials with permeability coefficient less than 10−4 cm/s are chosen for the shell, using this type of spillway would not endanger the stability of the downstream slope.

Results of Survey of Reinforced Concrete Structures of Drainage Gallery in Earh-fill Dam

The earth-fill dam of Zhiguli Hydropower Plant is located between the building of the hydropower plant and the concrete spillway dam. To collect seepage water in the body of the earth-fill dam throughout its entire length, inside a stone toe drain, there is a gallery made of reinforced concrete. In order to estimate the technical state, signs of structural deformation, cracks, chips and corrosive wear, a survey of the reinforced concrete structures of the drainage gallery with discharge outlets in the earth-fill dam has been conducted, the main results of which are presented in this paper.As a result of this survey, the areas and the value of subsidence of the reinforced concrete structures of the drainage gallery have been identified. The slope of the drainage gallery and the amount of sediment in it has been defined. Besides, the area along the route of discharge outlets has been examined, and the state of the coastline has been evaluated. Basing on the results of this survey, a detailed assessment of the technical state of the reinforced concrete structures of the drainage gallery in the earth-fill dam of Zhiguli Hydropower Plant has been given.

Technical visit: Shon Sheffrey spillway improvements

The British Dam Society (BDS) attended a site visit to Shon Sheffrey reservoir to see the latest progress on the spillway improvement works, where a new labyrinth weir and reinforced concrete spillway are to be constructed to the approximate alignment of the existing structure. The visit was organised by the client Dŵr Cymru Welsh Water, where BAM Nuttall Ltd are the principal contractor carrying out the works designed by Black and Veatch. Twenty-five members of the BDS attended the visit on Wednesday 25 June 2014.

Protecting roller-compacted concrete armored emergency spillway against uplift with geocomposite drain: Loxahatchee Reservoir example

ABSTRACT: When designing a roller-compacted concrete (RCC) spillway for a reservoir, seepage-induced uplift pressures need to be considered. This case study describes the design, construction and post-construction performance of a drainage system consisting of a geocomposite drain immediately beneath a stair-stepped RCC spillway at the Loxahatchee Reservoir in western Palm Beach County, Florida, USA. The installation comprised 2.8 km of RCC and a geocomposite drain to construct the fixed-weir emergency spillway. The primary stability issue for the spillway was the development of excessive pore water pressure beneath the RCC in the event of rapid drawdown of the reservoir. Transient seepage analysis predicted that installation of the geocomposite drain would eliminate excess pore pressures beneath the RCC, and dramatically increase the factor of safety against uplift (increased from 0.5 to a value of the order of 6), preventing structural instability of the spillway. Since placing the reservoir in operation, no structural instability has been observed in the spillway. Also, the absence of excess pore pressure is predicted by post-construction transient seepage analysis using reservoir operational-stage data.

Three-Dimensional Hydromechanical Sectional Analysis of Cracked Nonprismatic Concrete Spillway Piers

Several concrete hydraulic structures, such as spillway piers, must be considered three-dimensional (3D) components subjected to 3D loads. A very convenient approach to perform stability analysis of concrete dams is the so-called gravity method, leading to the solution of a PMM problem (axial force P and biaxial bending moments Mx, My) assuming linear normal stress distribution. If cracking takes place, water penetrates into the cracks, inducing the development of full uplift pressures (UPs). Sliding safety factors (SSFs) are computed using shear force resultants Vx, Vy, and a Mohr-Coulomb failure criterion while ignoring torsion T (VVT). This paper presents a 3D extension of the gravity method for cracked planar concrete sections of arbitrary geometry subjected to arbitrary loads (PMM-VVT). To compute the shear stress distribution, a VVT sectional analysis algorithm has been developed based on the theory of elasticity (TE), including Saint-Venant and warping torsional components combined with triangular 2D finite elements (FEs). Afterward, the SSF on the failure plane is computed from the integration of normal stresses on the remaining uncracked area where the Mohr-Coulomb criterion (considering the shear stresses from the VVT solution) has not been locally exceeded. Two validation examples and a case study of an actual pier are presented to illustrate the accuracy and efficiency of the proposed approach compared with full 3D FE analyses.

3-D dynamic analysis for earthauqke behavior of concrete spillway composed of T-shape piers and reverse L-shape piers against strong motions

3-D dynamic analysis for earthauqke behavior of concrete spillway composed of T-shape piers and reverse L-shape piers against strong motions