ABSTRACT. The Laúca hydroelectric power plant, located in the province of Kwanza Norte in Angola, in the final phase of construction, is one of the largest projects currently on the African continent. The main generation circuit of the project is located on the right bank of the Kwanza river, consisting of six water intakes.

The dam is of the gravity type and is being built with Roller-Compacted Concrete (RCC), with a maximum height of 132 m. The flood discharger is integrated to the dam, with control effected by three sluices segment. The Water Supply is composed of six island-type units with a total width of 162.0 m and a maximum height of 74.4 m since its foundation, being excavated in rock, downstream of the adduction channel. The forced tunnels, starting from the shafts to the generating units of the Main Central with a slope of 4%, have a section in rectangular arc with 9.00 m of width and 12,20 m of height, with average length of approximately 1,900 m. The Main Central (Powerhouse) is of the subterranean type, whose dimensions are: 20.60 m wide and 273.30 m long, and the assembly area is 80.00 m. The block width of each unit is 30.0 m. In the construction of Laúca, more than three million cubic meters of concrete were applied, among roller compacted concrete, conventional structural concretes and shotcrete. In this technical approach, the initial characterization of the concretes will be presented, emphasizing the alkali - aggregate reactivity studies for the two dominant rock lithologies that were destined to the concretes manufacturing.

ABSTRACT. Considering the importance and long lifespan of operating dams, it becomes important to analyze the observed structural response over time, and to compare the monitoring data with the response predicted using numerical models. In dam safety control, the following type of models can be used: i) numerical finite element models (FEM), based on the physical principles of structural mechanics (these are prediction models that can be used in the design stage as well as during the dam operation stage); ii) purely statistical models, reliant on past observation data, but deprived of any physical principles, being able to identify patterns in observed behavior; and iii) semi-statistical models, also named Effects Separation Models (ESM), based on basic physical principles used to determine a "model function", corresponding to a sum of simple mathematical functions, representative of the main actions effects, dependent of parameters that are calculated through a multiple linear regression to fit the "model function" in the best way to the observed results. With the purpose of detecting the abnormal behavior associated to a pathology like swelling, it is necessary to use the most robust effects separation models capable to distinguish normal time effects related with viscoelasticity from other time effects, e.g. related with swelling. In this work, a hybrid model is proposed, capable of gathering the key strengths of FEM and ESM. The presented results relative to the Aguieira dam’s structural behavior clearly show that the proposed hybrid model, that integrates statistical tools and expected physical response, gives an excellent adjustment to the monitoring results, showing that the proposed tool can be used in dam behavior prediction namely when swelling effects are present, as is the case of Aguieira dam.

ABSTRACT. The methods of modal identification can be divided into two main categories, methods in the frequency domain and methods in time-domain. This paper will only deal with the methods in the time domain. In order to estimate the modal parameters of a structure, two modal identification methods in the time-domain are used. For fully observed systems a statistical inference technique for the estimation of the parameters of a stochastic differential equation is applied, the so-called Maximum Likelihood Method (MLM). For partially observed systems is used the Covariance driven Stochastic Subspace Identification method (SSI Cov). Both methods are implemented in MATLAB and applied to the analysis of vibration test data from a building model of 20 floors and from an arch dam. The main goal of this paper is to contribute to the development and use of the time-domain modal identification methods for the analysis of ambient vibrations in large dams. The SSI-Cov method is tested in the Cabril dam using numerically generated acceleration records, through a finite element model of the dam (considering white noise type excitation), and then the method is used for the analysis of real dam vibration records from a continuous vibration monitoring system installed on site, since 2008.

ABSTRACT. The conventional method used to evaluate the safety of concrete gravity dams, does not directly quantify the effect of uncertainties on the safety of the structure. The theory of structural reliability, allows the quantification of the safety of these structures, from the quantification of the uncertainties inherent to the resistance parameters. This article illustrates the application of the theory of structural reliability to the concrete gravity dam through a hypothetical case study. The analysis is limited to failure modes related to sliding. The results demonstrate the lack of linearity between safety coefficients and reliability. Furthermore, the study shows which are the design parameters with greater influence on structures safety for the analyzed failure mode

ABSTRACT. Uncertainty affecting behavior of dams can be classified in intrinsic and epistemic. Objective uncertainties can be quantified in terms of probabilities, and used to evaluate failure probabilities of the dam. These are multiplied by failure costs, leading to expected costs of failure. Other uncertainties are subjective, and can be quantified only in terms of possibilities, i.e., using interval or fuzzy variables. In this paper, a methodology is proposed where the design of a gravity dam is made robust (less sensitive) w.r.t. subjective uncertainties, and optimal w.r.t. total expected costs, including construction and expected failure cost (risk). The application to a concrete gravity dam can be considered a sketch design problem, since only sliding and capsizing failure modes are considered. Solutions of the robust risk optimization problem proposed herein are compared to deterministic, reliability-based, and conventional risk-based solutions.

ABSTRACT. This work deals with ambient vibration tests performed in the section E of Itaipu Dam in order to estimate modal parameters (natural frequency, modal damping and mode shapes) in operational conditions. The study consists of experimental tests and theoretical modal analysis. The experimental tests were carried out by means of low-frequency accelerometers, placed in different point of the dam. The poly-reference least-squares complex frequency domain (PLSCF) method and covariance-driven stochastic subspace identification (SSI-COV) method have been used to evaluate modal parameters. The modal parameters identified using PLSCF method is in good agreement with the parameters extracted using the SSI-COV method. Furthermore, a finite element model of the section E Itaipu dam has been developed to verify dynamical characteristic, such as natural frequency and mode shapes with the experimental results.

ABSTRACT. This paper focuses on presenting DamDamage1.0, a 3D finite element based program for non-linear analysis of concrete arch dams, developed using MATLAB. The algorithm to perform non-linear calculations is based on a stress-transfer iterative method that accounts for the redistribution of unbalanced stresses in each iteration. The concrete behavior up to failure under tensile and compressive stress states is reproduced using an isotropic constitutive damage model with softening, which incorporates two independent damage variables: d+ for tension and d- for compression. DamDamage1.0 is used to simulate the non-linear static behavior of arch dams for a concrete strength decrease scenario: the aim is to determine a global safety factor λs that indicates the maximum admissible reduction of the material strength without causing the dam’s structural collapse. This failure scenario is studied for the case of Cabril arch dam (132 m high) using a 3D FE mesh with three elements in thickness, considering a load combination including the self-weight and the hydrostatic pressure at the upstream face. The non-linear analysis is performed using two constitutive damage laws to assess the influence of compression softening in the dam’s resistant capacity. The computed safety factors are compared with those obtained in previous experimental failure tests.

ABSTRACT. The main goal of this work is to contribute for the numerical simulation studies regarding the seismic analysis of large arch dams, by focusing on the influence of the reservoir water level in the structural response of the dam, for a given seismic accelerogram. Therefore, it is used a 3D finite element program (DynDam1.0) to compute Cabril dam’s seismic response in time domain, using a classic FEM formulation in displacements, through a modal decomposition analysis method. The numerical modelling of the dam-reservoir-foundation system is based on a classic model, using 3D finite elements with twenty nodal points to discretize the dam and the foundation, while adopting the added water mass solution of Westergaard to simulate the hydrodynamic pressures. The results of the seismic analysis are presented for different reservoir water levels, namely in terms of the maximum displacements at the top of the central cantilever, considering the use of several seismic accelerograms with varying frequency content which are scaled to a peak acceleration of 0.2g. The applied acceleration time histories were computed directly from a design code response spectrum.

ABSTRACT. The Teles Pires Hydroelectric Power Plant, in the Teles Pires River Basin, with an installed capacity of 1,820 megawatts, is among the largest hydroelectric plants in Brazil considering the installed capacity. The volume of concrete of the project, over 1,100,000 m3, corresponds to the sum of the massive and structural dam’s concrete. Several types of concrete were used, from wet mix shotcrete, RCC - (roller compacted concrete), and conventional concrete pumped for the most diverse applications. Considering the predominant use of pump concrete, in regions defined in Project where the RCC was not possible to be placed, it was necessary to make use of several resources, not only the concrete artificial cooling but also adding material of pozzolanic nature, in this case it was chosen Metacaulim HP as part of the cementitious material composition of the conventional concretes applied. Metacaulim HP as part of the cement was used in concrete mixtures with the initial objective of contributing to neutralize the alkali-aggregate type reaction (AAR) in the formulated concrete mixes. The replacement of part of the cement by Metacaulim HP assisted in the function of reducing the heat generated by the binder in the concrete mixtures applied in massive zones of the main concrete structures.

The benefits of using the binder also provided the modification of the concrete W/C ratio for hydraulic surfaces, based on abrasion studies in the concrete by the test method ASTM C1138.

ABSTRACT. Lime treatment of silty and clayey soils is a well-know and widely applied technique for soil improvement and stabilization of infrastructure works (roads, highways, airfields, railroad beds…). The use of lime treated soils in hydraulic context is less known, at least in Europe. However, several benefits of lime treatment for hydraulic structures construction or restoration were reported in the past: preventing softening while underwater (the lime-treated soil doesn’t revert to mud), preventing the leakage and resisting erosion from flowing water, reduction of shrinkage and swelling movements of high plasticity index soils (heavy clays). Testimonials of the application of this technique can be found in some places across United States and Australia since the 1970’s. The interest of the hydraulic works community regarding this technique is currently growing. During the last decade, the benefits of lime treatment and appropriate application technologies were evidenced for earthworks execution, for the improvement of mechanical properties and stability of structures, high internal and external erosion resistance of treated materials and the possibility to maintain low hydraulic conductivity values. These have been shown in the laboratory and for some properties with full scale experiments. The conferred soil properties can lead to innovative earthfill dams and dikes designs by addressing some of the typical designer’s problems, such as stability, watertightness, internal erosion, surface protection and flood control. The external erosion resistance was recently the topic of the French R&D program “DigueELITE” : in the frame of this project, an experimental earthfill dike was built along the river Vidourle (south of France) in July 2015, and tested against surface erosion (JET testing) and real scale overflow. Thanks to the information and large amount of results collected since 2005, it will be possible to provide guidelines for designing earthfill dikes and small earth dams resistant to mechanical and hydraulic stresses, using lime treatment and associated technology. This is a part of the objectives of a next ICOLD Bulletin CSD “Cemented Soil for Dams”, which is due to be published in 2020.

ABSTRACT. Most of the large Brazilian dams where developed in wide valleys. This condition led to the use of multiple types of structures in a single axis, such as embankments connected to spillways, intakes and other concrete structures. In Brazil, the most prevalent type of solution for such interfaces has been the use of a concrete gravity structure which is embraced by the embankment. However, other types of interface connection may be more efficient depending on the circumstances and the designer should look for the most efficient solution, which means an adequate water barrier with the least cost. This paper discusses the different types of interface geometry, comparing solutions employed in Brazilian dams. It focuses the most relevant geometric aspects of the concrete and earth structures and of filters/transitions in the contact, elements of utmost importance to avoid excessive flow and internal erosion of the core. The importance and limitations of field instrumentation of interfaces are evaluated. A comparison between gradients in different projects is provided to discuss how this parameter develops in such interfaces.

ABSTRACT. The objective of this paper is to present the initial steps on the design and study to zoned dam. The paper presents general guidance and is not intended to supplant the creative thinking and judgment of the designer for a particular project, but it must give to readers a brief summary of the sequence to initial study to design a zoned dam. The paper examines a few relevant aspects of the design and performance of a zoned dam. It covers the behavior of compacted soil and rockfill, the generation of pore pressures and deformations during construction, the stability of the Dam in order to find the most economical and safety geometry, the seepage phenomena during the operation of the dam and the important case of drawdown. The unsaturated soil mechanics offers today theories, experimental procedures and computational tools which provide a definite advantage over classical design methods; therefore, the present article aims to use this approach. It offers also a new insight into field observations. The use of unsaturated soils will give a better understanding of the influence of the water within the dam, and the importance of the climatic change in the life of the dam. The use of the analysis of unsaturated soils improves the design, cost and the stability of the dam in order to understand the behavior of it. The stabilization of a 100 m-high of a zoned dam located in a tropical zone is analyzed using seepage analysis, limit equilibrium methods and finite element methods. The use of the Seep/W, Slope/W and Sigma/W was able to capture the behavior of the dam taking into account the unsaturated soils of the materials, stability of the slopes upstream and downstream of the dam, deformations after construction and the case of drawdown of the water level. The seepage analysis was developed with the use of van Genuchten (1980) method, the factors of safety in different conditions were obtained with an approach of Morgenstern-Price method (1965) and the deformation analysis was done with the Mohr Coulomb failure criterion. The results show the stability in terms of seepage, stability and deformability of the dam from some basic field and laboratory tests, and it shows the parameters that were estimated.

ABSTRACT. The systematic and effective routine maintenance of the protection vegetation of an earth dam is fundamental to prevent the structure from surface erosion processes. Regions where brachiaria is present, maintenance is even more relevant, since its proliferation can make the structure more susceptible to superficial erosion processes. In the case of the Retiro Baixo HPP Dam, located in Curvelo/MG, brachiaria proliferated along the downstream slope of the earth dam. Its fast growth, combined with the absence of systemic maintenance, eliminated the protection grass existing in the structure and was responsible for the evolution of the surface erosion on the downstream slope of the earth dam. The return of effective and systemic routine maintenance of slope protection vegetation was decisive for the reversal of the condition. This study is an example of how the vegetation of slope protection on earth dams can contribute to dam safety.

ABSTRACT. The Valtorno-Mourão dam in the municipality of Vila Flor is intended to create a reservoir with the total volume of 1.12 x106 m3 for water supply. The embankment has a crest length of 150 m and 32 m of maximum height. It as a homogeneous profile including a sub-vertical filter. The construction of the dam took place between July 2004 and January 2006. During the first filling, important leaks where detected downstream of the dam, near the downstream toe. This leaks were aproximatly 10 times higher than it was estimated and two problems could arise. In one side, very high flows could cause erosion in the dam foundation, and, on the other side, the loss of water in one year represents aproximatly one half ot the reservoir capacity. Taking in consideration these two problems it was decided to reinforce the grout curtain in the dam foundation. After this a new first filling took place and the behaviour of the dam was satisfatory during that period. This paper describes more in detail the history of the dam and presents in detail the recorded behaviour during the 10 years after the rehabilitation and the first filling. The monitoring system allows for the record of seepage flow, piezometric levels in the dam and in the foundation, and external displacements (vertical and horizontal). According to the records the dam seems to exibith a satifatory behaviour and it is recomended to follow the monitoring activities in order to detect any possible change in this behaviour.

ABSTRACT. The seepage control in the core or foundation of the embankments, either during the design or the operation is one of the main requirements to be verified. Soil particles when subjected to a critical seepage can be carried or removed causing structural problems into the dam, characterizing an internal erosion process. The use of granular filters intends to interrupt the movement of the vulnerable particles, retaining them, progressively, inside the filter. Therefore, it is necessary the compatibility of the grain size distribution to the granular material and the fine material in the core, in order to provide constrictions with adequate size and frequencies according to the soil to be protected. The filter core material must have an internal stability, avoiding the fine fraction to be carried, in way to prevent the suffusion process. The methodology based on the size distribution on the constriction is required to evaluate the structure effectiveness in way to avoid the internal erosion and the core stability. This research intends to verify the core stability and the filtration effectiveness for the embankments design. The dams selected to the assessment of their internal drainage systems are Angicos, Bengue, Mosenhor Tabosa and Figueredo, located in the Ceara State, Brazil. The assessment uses the grain size distribution of the core and filter materials, highlighting the finest and coarsest materials separating each fraction of soil observed. These results show the inefficiency in the filter project for some of the selected dams, with greater incidence for cores with granular distribution of non-cohesive soils.

ABSTRACT. In the current situation of the Brazilian semiarid region, which depends highly on the hydraulic reservoir structures, an adequate design of water resource structures and maintenance of those already in operation is an essential factor to guarantee water supply and ensure the safety of the population who are downstream of the dam. Based on these necessities, a correct structural filter design is necessary, attributing its efficiency to the ability in preventing any internal erosion process. However, most of the dams in operation were designed before the publication of the present filter design criteria and those structures either do not have filters or have not a proper filter design, becoming more vulnerable to an eventual internal erosion process. The situation is further aggravated for embankments in the region with frequent droughts, due to constant drying and filling cycles of the reservoir, resulting in drainage system failure concerning to the soil fatigue during those cycles. It is therefore necessary methodologies for evaluate the risk of these structures against internal erosion process. This study describes an estimation for the effectiveness of the filter structure in the embankments, by using a numerical simulation of the contacts between the different soils and the structure through a geometric-probabilistic methodology, and using as input data the grain size distribution of the soils presents in the dam. The numerical modeling uses an alternative method of sizing filters, which correlates a theoretical approach of the subject. The dams select for the case study are Taquara, Olho Dagua, Figueiredo, Monselhor Tabosa, Itauna and Gangorra, all of them located in Ceara State, Brazil.

ABSTRACT. A dam breach is the worst event that can happen to this structure. To prevent this, an evaluation method should be used to rate and rank a dam. The main items to be examined on a dam are its purposes, construction methods, foundation kinds, layouts, size, length, spillway, operation and damage if it breaches, in other words, the vulnerability and potential damage of the dam. A safety dam federal legislation was approved in Brazil in 2010, and, according to this law, an official evaluation model was established. But was only after the Fundão Dam breach, localized in the city of Mariana, on November of 2015, that legislation and dam safety receive due attention in our country. Before that, there were some standards attempts used by private or public companies to evaluate dams that were under their control. Although there are some similarities, each model has its own way to rate the dam, which can mean different results. This article applies these methodologies on one small earthfill dam that breached and was rebuilt, and compare the results to check how the evaluation method can influence the outcomes or how the same structure can have different results according to the method applied.

ABSTRACT. There are different dam kinds, with particularities that make one kind to be better applied to some conditions. All of them look to suit the financial, technical, environmental and security requirements. Many times, one of these factors overlap others, that means that the structure doesn’t reach its goals fully. The financial factor is usually the most preponderant. In order to reach technical requirements, different calculation methods can be used to check the embankment stability on earthfill dams. Earthfill dams are the most common kind in Brazil, and many small dams are built using soils. This type of dam can be designed using simplified or more complex calculation methods leading to different slopes inclination angle, reflecting on safety and cost of the dam. This article compares different calculation methods, considering the same dam, that had a breach and was repaired quickly without any additional calculation, and check if it affects the earthfill design, security, stability on various situations, such as the reservoir fill, operation, the quick reservoir depletion and against horizontal forces

ABSTRACT. The paper regards the case study of the two spillway tunnels of 166.5 m high Fierza hydropower dam, in the Drini River in Albania, operated by KESH sh.a. since 1978. The study was carried out by means of a physical model at scale 1:80 and computational fluids dynamic models developed in LNEC. It focused on the jet flows produced at the exit of both spillway tunnels and their impact on the downstream river bed and slopes. The study allowed to produce recommendation measures in order to prevent observed slope instabilities and erosions downstream, as well as to assess the flow interference of an existing road bridge located approximately 500 m downstream of the powerhouse race tunnel, located at the dam toe. The spillway is formed by two concrete lined tunnel spillways in the right bank: Tunnel No.3 with maximum capacity of 1780 m3/s; and Tunnel No.4 with maximum capacity of 890 m3/s. The terminal structures of each tunnel consist of flip buckets with asymmetric geometries in order to direct the water jets into the river bed near the road bridge and between the spillways’ flip buckets and the downstream road bridge. Since the dam entered into service the operation of spillway tunnels has been ensured solely operating the tunnel No.4. Even so, damages have been observed in the let bank slope and the road bridge. Also, since then, some concerns have developed about safety of the slopes and the road bridge in case a major flood event or a problem with Tunnel No.4 requires operation of the spillway Tunnel No.3. Therefore, the simulation of the operation of the spillway tunnels No.3 and No.4, under different combination of discharges, was performed using both numerical and physical modelling, in order to characterize the spillway operating conditions on the hydraulic point of view. This paper summarizes the performed tests/simulations, respective results and recommendations, and it is intended to evidencing the advantages of using traditional hydraulic physical models together with the recent CFD approaches, which use in the hydraulic structures field is increasingly growing.

ABSTRACT. On the last decade, there were built in Brazil large spillway structures in relevant rivers under challenging schedule conditions. This paper presents aspects of planning and construction of the following spillways: Santo Antonio HPP (capacity: 84,000 m³/s through 18 radial gates in the Madeira river), Belo Monte HPP (capacity: 62,000 m³/s through 18 radial gates in the Xingu river) and Baixo Iguaçu HPP (capacity: 53,585 m³/s through 16 radial gates in the Iguaçu river). In terms of schedule, world records have been achieved for that kind of structure, revealing the Brazilian dam engineering capacity of accomplishment. The constructive methodologies presented in this paper evidence the Brazilian state of the art on large spillways construction. The main elements of a sliding formwork system and the schedule savings are presented. It is demonstrated that the use of sliding formwork in large spillways pillars allows economy of time in order of 60%, embodying in an important tool whether for fulfilling of daring timetables, or for recovering of schedule in case of eventual unforeseen externalities. It is emphasized that the success of the sliding process in huge structures depends on the adequate use of the trinomial: (i) reinforcement and embedded items pre-assembling, (ii) on-time pumped concrete technology, and (iii) the sliding formwork system itself.

ABSTRACT. The Panama Canal expansion project, opened to traffic in June 26, 2016, involved the addition of 6 locks to the 77-km long navigation canal connecting the Atlantic with the Pacific Ocean. The new locks increased the canal width and depth to support modern container ships up to 12.600 TEU. To save water of Lake Gatun for the operation of the locks, 18 Water Saving Basins, 9 on the Atlantic side and 9 on the Pacific side, were built and waterproofed with Polyvinylchloride (PVC) geomembranes and geocomposites. The normal operation of the basins accounts for 14 filling/emptying cycles per day. The adopted PVC geomembrane was selected because of its high flexible elastic properties and expected durability in excess of 100 years. The geomembrane system lines the dams and bottom of each basin, and the joints at the concrete partition walls, for a surface of about 600.000m2, with the PVC liner in direct contact with the excavated soil or earth-fill. The waterproofing liner is a geocomposite consisting of a PVC geomembrane, 3.0mm thick on the slopes and 2.5mm thick on the bottom, heat-bonded to a polypropylene geotextile with 500g/m2 mass per unit area. The forces considered by design were uplift by wind and hydrodynamic water pressure, erosion due to fluctuations of water level, sliding of slopes, and ground geotechnical conditions. The subgrade changed without regular pattern from Gatun rock to clay, excavated basalt or rock/soil filling, concrete, shotcrete, requiring different anchorage systems: deep soil anchors, tensioning profiles and trenches, ballast trenches, ballast concrete blocks, which hold the liner against the subgrade resisting all the mentioned forces. The design underwent optimizations and changes to adapt to the site conditions, which was possible due to the flexibility and adaptability of the system, and the expertise of the contractors and designers. Installation works were completed in less than a year, in difficult weather and site conditions, and they fulfilled all the contract requirements and passed all tests on completion.

ABSTRACT. During the construction of the spillway of La Potra dam in Panama, it was verified that part of this structure would not be based on rock, but on unconsolidated materials of great heterogeneity known as Lahars. Exploring surveys confirmed the occurrence of Lahar in great depth at the site, which would make its removal a non-viable solution. Thus, further field investigations were initiated in order to evaluate the Lahar bearing capacity, acting as the underlying material for the spillway foundation. Bearing capacity estimates of shallow foundations are usually performed through parameters that come from field investigations such as SPT (Standard Penetration Test), CPT (Cone Penetration Test), as well as plate load tests. However, the performance of such tests may prove impractical in heterogeneous unconsolidated materials, as the case of Lahars. Therefore, this paper aims to present the alternative method chosen to evaluate the Lahar bearing capacity, which will constitute the underlying material of the spillway walls foundations. The selected alternative consists in a group of pressuremeter tests (PMT) whose results were used in a semi-empirical method which is not commonly practiced in foundation engineering for bearing capacity estimations of shallow foundations. The performance of PMT tests proved to be efficient mainly due to the results repeatability. The use of the semi-empirical method demonstrated that the local Lahar is able to receive the spillway walls load requests. Analytical and numerical settlement estimations showed coherent and compatible with each other. Furthermore, Lahar field strength parameters were assessed, specifically regarding the cohesion values which ranged between 60 and 140 kPa.

ABSTRACT. An important tool for the maintenance and monitoring of dam safety is the preparation of flood forecast maps due to structural failures that may occur in these infrastructure works. Often, in areas downstream of dams, it is possible to identify urbanized regions, or exposed soils that intensify the catastrophic potential of an extreme flood. Thus, using flood forecasting, owners, public agencies and the riverine population can work together developing predictive actions, for the sake of safety and safeguarding the well-being of all. The hydrodynamic modeling obtained through software is a strategic resource for the simulation of flood spots from hypothetical dam ruptures. The results generated from this methodology provide important parameters of wave propagation analysis, such as velocity, water depth and affected areas, serving as subsidies for the elaboration of emergency plans. For the calibration of the modeling, among several information, is used the roughness coefficient obtained through the characterization of the vegetation cover of the areas on which the flow will occur. Thus, the present work proposed, from the survey of already existing references and researches, to evaluate the influence of the coverage of downstream areas, in relation to the main runoff and the flood plains and, consequently, the roughness coefficient, on the characterization parameters of the flood waves produced by the computational hydrodynamic modeling. It was concluded that the value of Manning, composes the list of determining factors on a characterization of flood waves from hypothetical dam ruptures.

ABSTRACT. Stepped spillways have become an appropriate alternative to many dams worldwide because of its ease of construction and economy. Another advantage of the use of this type of structure is the significant energy dissipation along the chute, caused by the macroroughness of the steps. However, the use of this structure may be limited due to the risks of cavitation at the steps, associated to the occurrence of significant pressure fluctuations and extreme negative pressures. With the objective of studying the risk of cavitation in steeply sloping stepped spillways, experimental tests were carried out on a stepped chute assembled at the Hydraulic Research Institute of Federal University of Rio Grande do Sul (IPH/UFRGS), in Brazil. The mean and extreme pressures associated with the non-exceedance probabilities of 0.1% were analyzed near the step edges. The analysis of the extreme negative pressures scaled to appropriate prototypes suggests that cavitation tendency may occur in the vicinity of the point of inception for unit discharges larger than about 11 to 17 m2/s.

ABSTRACT. This paper presents the main challenges faced in the project and operation stage of the spillway of Tucurui Hydroelectric Power Plant. The design changes that allowed the reservoir to rise the operational level and the fatigue ruptures of the movement rods of the spillway floodgates are discussed in this paper. These design changes provided greater operational safety to the spillway, avoiding damages to the riverine population, unfavorable conditions to navigation in the downstream or upstream stretch, defluent hydrographs higher than those recorded before its construction. Moreover, these changes enabled to increase the production capacity.

ABSTRACT. The constant transport of sediment to the Santo Anastácio dam has been decreasing its capacity over the years. The small dam was built in the 1918s and is one of the oldest reservoirs of the city of Fortaleza, with a water storage capacity of 508000 m³ by the time of its construction. The present work analyzes the current situation of the dam, showing mainly the environmental degradation. The dam, which is in the Federal University of Ceará, Brazil, has a compromised storage capacity as well as a strong environmental impact because it is in an urban and densely populated area. We have observed problems such as Eutrophication, fish mortality and a large amount of both solid and liquid waste, which lead to serious problems for the water resource. With the increase of sediment deposition in the dam, that is, an increase in siltation, will cause the water resource to collapse in a short time.

ABSTRACT. The state of Ceará is inserted in the semi-arid region, where there is a shortage of water. In order to mitigate the drought problem, both federal and state governments have built a dam. The present work shows an analysis of the conditions of the Carão dam in the municipality of Tamboril in the state of Ceará, Brazil which has a storage capacity of 22 million cubic meters of water. The dam is used for human supplies, fish farming, recreation and watering of animals, but it presents a series of environmental impacts as it is also currently practically dry due to the lack of rainfall in the region.

ABSTRACT. The government of Minas Gerais, through the State Foundation for the Environment (FEAM), has been developing, since 2002, the Tailings Dams Management Program which the purpose is to reduce the risk of environmental damage as a result of failure in these areas, following the guidelines of COPAM Normative Resolutions 62/2002, 87/2005 and 124/2008. Therefore, this work aims to show the actions of the government to improve the safety conditions of tailings dams’ existent in the state of Minas Gerais. In 2015, after the Fundão tailings dam (“Fundão Dam”) failure, operated by SAMARCO MINERACAO SA, one of the actions of the State Government of Minas Gerais was to create a Task Force on dams, which purpose was to diagnose, analyze and propose changes in the standards and techniques used in the disposal of mining tailings. The work was coordinated by the State Secretary for Environment and Sustainable Development (SEMAD) and by FEAM, with the participation of several State Secretaries, representatives of the productive sector, public entities and universities. Another important action after the failure was the training offered by Feam, with the objective of presenting the main factors to be evaluated in a dam inspection and the main problems that can occur when carrying out inspections in these structures. As a result of the discussions of the Task Force, it was concluded by the adoption of measures that could reinforce the safety of existing dams in the state of Minas Gerais. The evaluation of these points made possible the establishment of Decree 46.993/2016 and of the Joint Resolution SEMAD/FEAM 2.372/2016. The Decree establishes the Extraordinary Tailing Dam Safety Audit, required for tailings dams raised by the upstream method and the Resolution establishes the guidelines for that accomplishment, in addition, the described trainings resulted in the formation of teams for a campaign of inspection, which resulted in 309 structures inspected in 2016.

ABSTRACT. To operate with sustainability, mining companies around the world have made large investments to consolidate the vast amount of data and information regarding their operations. The quality of this information is of fundamental importance and is directly linked to the valuation of mineral activity and its interaction with society. Specifically, in terms of Dam Safety, the confidence and availability of these data has become vital, especially after the breakup of the Fundão Dam, in Mariana-Minas Gerais, in November 2015. As a result of this scenario, on 05/19/2017 the Brazilian government, through the National Mining Agency published in the Official Journal the Ordinance Number 70.389, which establishes, among other items, a series of articles in which entrepreneurs of mineral extraction should adopt to inspect and monitor their geotechnical structures (for example, slopes, dams, embankments, landfills, mine pitches, among others), in order to ensure that the research and mining activities are performed in accordance with the National Policy on Dam Safety. In this paper, will be discussed some technological solutions to comply with the new ordinance for dam safety in Brazil. One of the technological solutions is the Slope Health Monitoring System (SHMS), developed by Intelltech, which is a modular platform for integrating geotechnical data, planning of monitoring and inspection activities, data analysis, risk management, and the provision of information to support and mitigate the uncertainties associated on the decision-making processes in geotechnical monitoring. It will be explained how this solution meets the requirements of the Ordinance 70.389/2017.

ABSTRACT. Robotic underwater inspection and construction services in Tailing Dam using a ROV – Remoted Operated Vehicle.

This abstract is about an underwater robotic service that Hibbard Inshore provided to one of the largest Brazilian mining companies at one of their existing tailings dams.

The main issue was to understand the general condition of a lower outlet tunnel in order to plan and design a permanent bulkhead for abandonment of the tunnel. The tunnel was water-filled, and due to the unknown condition, the owner had concerns that if they were to dewater it, the removal of the water could increase the risk of destabilization or collapse. Because of this, the owner determined it would reduce risks by first inspecting the tunnel condition while it remained water-filled.

Hibbard Inshore was hired for the underwater inspection the tunnel using a ROV with video and sonar units. The high-water turbidity required the sonar to be used as the primary inspection tool. During the inspection Hibbard Inshore identified a very high level of debris and sediment in the tunnel creating a blockage in the tunnel.

As a result of the inspection, the client is pursuing further action to remove the blockage while the tunnel remains water-filled and to further evaluate the tunnel. Additionally, the the client was able to plan a different method and approach to bulkhead the tunnel than had originally been devised.

ABSTRACT. There is a growing need to guarantee the safety of the existing dams in the country, especially after the Fundão tailings dam (“Fundão Dam”) failure, operated by SAMARCO MINERACAO SA, on November 05, 2015. There are a few ways to ensure the safety of these structures, such as proper management of the construction and operation processes. This work is focused on the structure management stage and aims to define guidelines for the Tailing Dam Safety Audit, with the purpose that safety become paramount during their operation. As a methodology, in a partnership between the Núcleo de Geotecnia da Escola de Minas (NUGEO) and the Fundação Estadual de Meio Ambiente (FEAM), is being performed an analysis of the Extraordinary Tailing Dam Safety Audit Reports, required for tailing dams raised by the upstream method, whereas, as regard to safety, this type of dam requires more stringent criteria in construction, operation and monitoring. The data obtained in this analysis will be confronted with the Regular Tailing Dam Safety Audits held periodically in accordance with COPAM Normative Resolution 87/2005. Among the expected results, we can mention the construction of a database with the information of the tailing dams raised by the upstream method. The analysis of the results will define guidelines that may assist in a possible standardization of the Tailing Dam Safety Audits, performed periodically, helping the government in the fulfillment of its function and the entrepreneurs in the definition of the basic items to be studied, always aiming for the structures to be increasingly more secure.

ABSTRACT. Rock-Filled Concrete (RFC) is an innovative mass concrete technology. To date, RFC technology has been used to build a great number of gravity dams and arch dams. Since it was invented in 2003, many experimental and numerical research works have been conducted. During the construction process of RFC, an assembly of large rocks with more than 300 mm in grain size, called rockfill, can be cemented with a high-performance self-compacting concrete (HSCC). The RFC technology combines the advantages of masonry and concrete, in that it decreases cement consumption, lowers temperature rise of cement hydration, and reduces shrinkage of concrete. This paper aims at acquainting readers with a timely review of state-of-the-art research on RFC technology, including (1) workability of HSCC and compactness of RFC, (2) thermal and mechanical properties of RFC, (3) structures of an RFC dam and (4) construction and quality control measurements.

ABSTRACT. During the 1990s, stabilization of the upstream slope of Concrete Face Dams were executed by compacting horizontally the cushion zone 2B and the upstream slope by a vibratory compactor in the up and down direction with the addition of asphaltic emulsions to provide some cohesion. This method was time consuming since it was necessary to stop the 2B placing to stabilize the upstream face. In 1998, during the construction of the Itá Hydroelectric Project (Brazil), a new method was developed by using an extruding concrete curb machine to confine the cushion 2B in a fast and productive way, which quickly became the world standard for the execution of the upstream slope of CFRDs. International experts called this procedure the “Itá Method”. This paper presents the process of development of the “Itá Method”, and its economic and chronological advantages, responsible for its fast worldwide diffusion. It also shows an updated overview of the application of this method in the many continents of the world.

ABSTRACT. Concrete face rockfill dams (CFRDs) are becoming a widely used type of rockfill dam all over the world. Few numerical or analytical methods have been developed to properly evaluate the deformation of CFRDs, which is important for dam safety and for subsequent evaluation of seismic performance. This paper describes the setup of a finite element method (FEM) model for the three dimensional simulation of the construction of Montesinho CFRD and filling of the its reservoir using the Code-Aster code. The prototype of the study is the 36.5 m high Montesinho CFRD, located in the north of Portugal near the Spain border, in the Sabor river in the Montesinho Natural Reserve, witch has been completed in 2016. Settlement is one of the most important deformation characteristics of a CFRD and is regarded as a key indicator of dam safety. The time-dependent settlement behavior of Montesinho CFRD is studied on the basis of in situ settlement-monitoring records. They were obtained from a settlement monitoring system established to monitor the deformation of the Montesinho dam. The monitoring results covered the construction period, the initial filling of the reservoir and 2 years of operation. Several elastoplastic models (Druker Prager, Cam Clay) were implemented to better model the rockfill materials. The model parameters were calibrated by large-scale triaxial tests, performed on materials used in the dam. The step-by-step construction followed by subsequent impounding of the reservoir was simulated in the numerical procedure. A numerical analysis on the settlements and stability of the dam was conducted and its results were compared with the field measurements. The numerical results agree well with in situ monitoring records of dam settlements, indicating that the developed three-dimensional finite element procedure can be used to evaluate the deformation of CFRDs. Furthermore, the deformation in the next 3 years is predicted. Overall, it is demonstrated that these models are able to address the complex behaviour of rockfills and are a valuable tool in the design and performance analysis.

ABSTRACT. The safety evaluation of existing dams is an engineering practice whose primary aim is to evaluate a project’s premises in order to adequately manage structural safety and, in addition, provide information for the development of future projects. The interaction between personnel involved in design, construction and operation during the safety re-evaluation is pretty important to share knowledge and guarantee a consistent, reliable and effective analysis of the structure behaviour. The article presents the actual behavior of the Irapé Dam, considering the particularities of this project, after 11 years in operation, and evaluating the effects of the standards used to manage its structural safety. Irapé is a clay core rockfill dam, which has a maximum height of 210m, the highest in Brazil, and a total crest length of 560m. In terms of site geology, the main characteristics, which conditioned the design solutions adopted, are a high sulfide concentration in the rock (mainly pyrite and pyrrhotite) and a very narrow valley shape. The sulfide concentration reaches 10%, an unusual condition when considering the rock foundations of similar-sized dams. The work carried out by Cemig (dam operator) and Intertechne (designer) to evaluate the safety of the dam comprised a site inspection and 3D numerical modeling using parameters calibrated from instrumentation data and the re-evaluation of instruments threshold values for piezometric levels, percolated flows and stress-strain. The results of the re-evaluation showed that the dam behavior is adequate considering current operational conditions and that the premises adopted in the design phase are still valid.

ABSTRACT. To use rock in engineering applications, certain properties of the rock must be assessed to reasonably predict its performance. The properties of rock fall into two broad classes: rock material properties relating to the rock itself and rock mass properties relating to the in-place rock mass, including its discontinuities. Rock material properties are related to the physical properties of the rock-forming minerals and the type of mineral bonding. They are essential in assessing hydraulic erodibility of rock and include rock type, color, particle size, texture, hardness, and strength. Seismic velocity, weathering, and secondary cavities are properties related to both the rock material and the rock mass. The rock mass properties are the lithological properties of the in situ rock that must be evaluated on a macroscopic scale in the field. These would include features such as fractures, joints, faults, bedding, schistosity, and lineations, as well as the lateral and vertical extent of the rock unit. The properties of a rock mass are significantly different from the properties of samples of the same rock mass. The strength and mechanical behavior of the rock mass are commonly dominated more by the nature of its mass properties than by its material properties. Material properties tend to control the strength of the rock mass if discontinuities are widely spaced, or if the intact rock material is inherently weak or altered. It is important to recognize that many rock properties interact under performance conditions. A performance assessment for any given engineering application must be viewed in the broader context of these interactions. This paper discusses the necessity of applying, as routine, simple laboratories investigations such as optical microscopy, X ray diffraction and ethylene glycol immersion in the rocks that are to be used as rockfill or riprap, in order to identify the presence of susceptible mineral to chemical or physical weathering. This study is important to prevent the use of inadequate material that might imply in premature reworks. Here are presented three case studies of Brazilians dams. These studies were carried out with basalt, diabase and with a metagraywacke.

ABSTRACT. The revaluation of loadings applied to dams (augmentation of hydrology or seismicity) as well as the evolution of design criteria (new methodologies or augmentation of safety factors) lead to the reassessment of the stability of existing dams. In this context, the characterisation of the mechanical properties of the weaker parts of the structure, that govern the failure mode, is of a main concern. For concrete dams and more particularly for gravity dams, the failure mode is most often linked to the concrete-to-rock interface between the dam and its foundation.

The French utility company EDF (Electricité de France) operates more than 350 concrete and masonry gravity dams. The improvement of concrete-to-rock interface characterisation is therefore an important issue.

Over the last few years, EDF has launched several research programmes to better characterise this concrete-to-rock interface with: - A database and a methodology for the determination of the tensile strength, - 2 thesis that deal with the estimation of shear strength and its scale effect, - The geometrical characterisation of existing dam-foundation contacts using non-destructive investigations. Other actions concerning numerical modelling tools of the concrete-to-rock interface are also going to be developed.

The main results of this research can already be applied to gravity dams but also to other concrete structures built on rock foundations such as thrust blocks of arch dams or penstock anchor blocks.

ABSTRACT. The operation of Capivara hydropowerplant started in 1977. The design considered that uplift at the powerhouse, which consists of four units, would be negligible. In 2002 a safety review recommended the measurement of uplift in this structure and therefore four Casagrande type piezometers were installed both in the foundation and at the concrete-rock interface of two units. During three years a continuous evaluation of the instrumentation was carried out showing that the uplift was under control. However in 2015 a new safety review found out that the piezometric values rose above the expected values and the calculated safety factor against flotation for the usual load condition, although higher than 1,0 was below the recommended criteria established by Eletrobras, that is 1,30. Therefore a new stability analysis was carried out confirming the previous conclusion and steps were taken to reduce uplift in order to assure an adequate safety factor against flotation. More piezometers were installed and a drainage curtain with 26 holes was devised to be drilled in up to four stages. When the second stage was ready and therefore only 12 holes were drilled the uplift immediately dropped and the desired safety factors were achieved. The main conclusions that can be taken from this case is that a good monitoring system is of paramount importance to guarantee structural safety of dams and that the periodic safety review process by a team of experts is very important and valuable for a perfect diagnosis of a dam and to identify potentially problematic issues that can occur.

ABSTRACT. Crosshole seismic tomography method may be used for assessing the mechanical properties of dam’s rock mass foundations. With this method the whole rock mass foundation along dam’s reference profile was cover providing relevant data about its geomechanical characteristics as the location of discontinuities and weak zones. This paper presents the crosshole seismic tomography characterization of Baixo Sabor dam’s rock mass foundation in terms of P-wave seismic velocity. There is also presented its contribution to the finite element model that supported the analysis and interpretation of dam´s structural behaviour during the first filling of the reservoir that took place from December 2013 to April 2016 and the subsequent operation period until late January 2017. Geological-geotechnical characterization of Baixo Sabor dam and seismic tomographic profile by its reference line are presented, allowing to verify their good general fit, namely the fair (GZ2) to good (GZ1) quality granite to which correspond relative higher seismic velocity zones. Moreover fractured and weathered rock (GZ3) is associated with relative low seismic velocity zones. This seismic velocity zoning was used as one of the tools to mechanically characterize the dam’s foundation, as a complementary tool to calibrate the mechanical parameters for the modelling of the dam’s structural behaviour, namely for the foundation deformability action. The characterization of the materials’ properties (concrete and rock mass foundation) and of the actions and responses during the first filling of the reservoir, as well as the structural model used to simulate the structural behaviour, are presented. This model included a 3D representation of the dam and its rock mass foundation and it was analysed by the finite element method, considering the actions time evolution, the foundation deformability and the concrete viscoelastic behaviour. A good agreement between the monitoring results and those obtained through the mathematical modelling was achieved, which confirmed the good performance of the dam and the modelling adequacy during this important stage.

ABSTRACT. Current design and construction of large dams follow international guidelines developed over the past several decades of observations, analysis and expert deliberations. These guidelines are routinely updated as new observations, performance evaluations and interpretations are made. The established guidelines, without completely ruling out the design and construction of dams on marginal and poor foundations, recommend and emphasize instead that appropriate engineering judgement be made in the design and construction, as the need to make up for the lack of good sites have arisen. Thus ensuring the adequacy and competency of a foundation for the selected dam type has to be reasonably established at the feasibility study stage, prior to the issue of contract tender documents for competitive bidding. The Client must also be made aware of risks if they are manageable, in view of the large investments needed. Composite dams, as a potential solution, are now gaining acceptance for designing and constructing large dams on very weak foundations that may have been considered as unacceptable in the recent past. Most of these poor sites are also in areas prone to higher seismicity thus making the solutions both complex and tougher. An essential part of the composite dam design and construction philosophy is to place flood evacuation and headworks structures on the more competent foundation part along the dam axis, if and when other options are not feasible and/or are ruled out; a central core rockfill construction is preferred for the flexible part of the dam or over faults and fault zones crossing the dam axis. This paper presents lessons learned and key observations from recent composite dam design and construction, along with an outline of a proper approach to avoid pitfalls, cost overruns and project delays. Suggestions for early design considerations to provide implementation options for foundation and abutment improvements with appropriate construction timelines are also provided.

ABSTRACT. This work was undertaken in Furnas Centrais Elétricas S.A. and presents the results of a research concerning some surge flow in drainage galleries from two dams. Those occurrences were observed during the filling period of their reservoirs. The materials collected from one of the dam’s presented slurry consistency with beige color; in the other dam, the materials consist of several spherical particles of small dimensions, with similar color from the first.

Several laboratory studies were performed using different techniques in order to obtain the chemical, physical and morphological characterization: X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray microanalysis, X-ray fluorescence spectrometry and laser granulometry. As a complement, water, soil and rock samples of the dams were also analyzed in lab.

The results indicated calcium carbonate as the main constituent with some other minor constituents. A high electrical conductivity of the water in contact with those materials was also observed, what differs from the river water of one of the studied dams.

One possibility to explain this phenomenon would be the leaching of concrete residual material from its open voids by the water during the reservoir filling. This would be carried out through the drains, concentrating specially calcium. The observed morphology of the materials can probably be explained on the water movement along the drains, although supplementary studies are necessary to aggregate more information.

ABSTRACT. Monitoring instruments are fundamental to evaluate the safety of a dam in the operational period, regardless of their purpose. The analysis of the instrumentation readings can help the safety engineering team to obtain responses on the behavior of the dam over time, indicating trends that can anticipate prevention and mitigation actions. The question that exists about the domain of variation of a certain instrument is: based on whether engineers can claim that their behavior is 'under control' or 'outside of control'? It occurs that this domain of variation, often determined in the planning of the dam, does not correspond more to the reality of the data provided by the instrumentation and this does not mean that the characteristic that the instrument evaluates is 'out of control'. In this case, we should not ignore the instrument, but rather 'calibrate' its limits of variation. In this paper, we used a statistical quality control tool, the control charts, to establish the control limits for the values of the dam monitoring instrument reading. In particular, considering the auto dependence in the time series data of an instrument that monitors the dam of the Itaipu Binational hydroelectric power plant, we adjusted an autoregressive integrated of moving averages with seasonality model to the data of the time series. Then, following the specific literature, we establish statistical limits of control for the time series of residues and their amplitudes, where residual is the difference of the established model and the real data. Certain theoretical assumptions, as the data follow a normal probability distribution, may not be present in the available data and the control limits need to be calculated according to some more appropriate probability distribution. The results show that based on the calculation of a probability we can respond if that instrument is, from the statistical point of view, under control, make future forecasts and monitor if it remains under control. In this way, the statistical model of control charts is an auxiliary tool to the dam safety team, with a theoretical basis, to evaluate and 'calibrate' the limits of variation of a given instrument.

ABSTRACT. The Foz Tua Project is the latest accomplished hydroelectric investment of EDP - Energias de Portugal, located in a tributary of Douro River, close to its mouth, in the northeast of Portugal, which includes a concrete double curvature arch dam 108 m high with a total crest length of 275 m, closing a narrow granitic valley. After a brief presentation of the project, the monitoring system is introduced, reporting namely the automatically controlled remote observations. The overall characterization of the behaviour evolution is presented, noticing the perceived agreement between observations in redundant systems, as well as the sought correlation between related physical quantities. Furthermore, some minor inelastic behaviours related to local adjustments of the dam/foundation structure, as well as the improvements in the designed foundation drainage and piezometric networks which were implemented accordingly to the foundation hydraulic behaviour observed in the last impoundment stages, are also commented. Bearing in mind the adequate behaviour during the first filling of the reservoir and the good fitness of a nonlinear finite element model it was concluded that the dam is apt to the following serviceability state.

ABSTRACT. Baixo Sabor dam, whose construction was completed in 2014, is located in Sabor river, one of the right side tributaries of the Douro river, in the North of Portugal, is a double curvature concrete arch dam 123 m high, engineered and constructed by EDP Produção a company of EDP-Energias de Portugal Group. The first filling of the reservoir took place between February 2014 and April 2016. The dam safety monitoring plan was defined during the design phase. It was implemented considering the most suitable measurement instruments to monitor the behavior of the dam during the first filling of the reservoir and the exploitation period. This paper explains the criteria adopted in the definition of the manual data acquisition system to control both the actions applied on the dam and capture the structural response under static loads. It also describes the automatic data acquisition system that completes and validates the data acquired with the manual data acquisition system and some relevant results are presented. Additionally, the dam was equipped with a vibration based structural health monitoring system, composed by 20 uniaxial accelerometers. This paper also describes the main characteristics of this system and the results obtained during the first filling of the reservoir and initial stage of exploitation. These results include the characterization of the accelerations amplitude and the evolution of the dam modal parameters, being particularly interesting to observe the influence of the water level on the modal parameters and the development of statistical models taking into account this effect.

ABSTRACT. Repair materials can improve substrates properties besides those for which they were designed, i.e., a material for waterproof and surface protection can contribute to the residual strength of beams, due to its penetration via cracks, becoming an integral part of the concrete, sealing empty capillaries and shrinkage cracks. In the present work, compressive tests and inverted Four-point Bending tests were carried out in concrete cylindrical and beams samples with and without permeability-reducing concrete admixture embedded in the mixture, cured in wet chamber for 28 days. After load application until the beams cracking moment up to 0.4mm, a crystalline waterproofing coating material was superficially applied on those cracks. The treated beams were stored in water immersion curing for more 28 days. The analysis of 56-day residual resistance improvement was held, subjecting the prismatic specimens to new bending test. Compressive strength was not influenced by admixture A pre-addition in concretes. In the other hand, small increase on stiffening at the initial reopening of main crack of beams at flexural tensile strength was observed.

ABSTRACT. The Hydropower Project is located in the Peruvian region, in a complicated environment that merges both Andean and jungle conditions. In these rainy areas, geologic and geotechnical conditions, combined with a strong seismic activity, lead to many constraints for the design of hydropower projects. Steep boulder-bed rivers, occurrence of debris-flow events and poorly characterized soil conditions along the conveyance system require that the design of the project perfectly combines feasibility and proper scheme performance, while keeping in mind the difficult operation and maintenance of a project located a several-hour drive from the next big inhabited center. The project consists of two water intakes located in two different rivers that convey the flow to the forebay and the penstock by means of two large box culverts. The starting point for both intakes is a Tyrolean weir, which safely provides the water intake point while minimizing the harmful debris normally occurring in the catchment areas. Flow debris events, referred to as “huaicos” by locals, represent a breakpoint in which a Tyrolean weir is a good option to cope with the presence of a strong flow of mud and boulders that may damage and leave out of operation the hydro-mechanical equipment of a classic gated weir. This paper introduces the main aspects considered for the design of the intake works, explaining the final solution adopted for construction and its main key components.

ABSTRACT. Flood propagation due to dam break was studied by means of a distorted physical model of Ürkmez Dam, built in the open area of Hydraulics Laboratory of Dokuz Eylül University. The physical model with a horizontal scale of 1/150 and vertical scale of 1/30 contains the reservoir, the dam, and the downstream part of the dam until the sea. The residences and the main highway were also represented in the physical model. The dam break problem was investigated by generating three different flood hydrographs. The water depths were measured by using e+ WATER L sensors and the velocities were determined by UVP transducers. The propagation of the flood was recorded by a HD camera. The experimental results obtained from different flood hydrographs were compared and interpreted. The experimental findings obtained from the physical model were also converted to those corresponding to the prototype.

ABSTRACT. The description of the flow in stilling basins is complex and the flow patterns has great interest to better access the behaviour of such hydraulic structures and improve their design. Measurement of pressures and velocities allows the knowledge of the flow characteristics and its actions on hydraulic structures. These measurements are commonly performed in physical models and rarely done in prototype. Therefore, data from prototype measurements has a large technical-scientific interest and can generate useful information for future projects and works, remaining its acquisition a technical and research challenge. The purpose of this article is to present a combined system to measure directly hydrodynamic pressures as well as flow velocities close to the bottom of a plunge pool of a dam subjected to jet impingement and to address its hydraulic behavior. The hydrodynamic pressures, mean and fluctuations, are measured by commercially available pressure sensors, designed for continuous pressure measurement in water environment. Velocities are measured by new 2D water flow sensors based on the principle of heat dissipation and two-dimensional flow vectoring specially designed for plunge pools as no commercial sensors existed to measure the water velocity in the target conditions. The system presented was implemented in the Foz Tua’s plunge pool, downstream of the 108 m high arch dam owned by EDP – Gestão da Produção de Energia, S.A., that has been recently constructed in the Tua river, a right bank tributary of Douro river, in Portugal.

ABSTRACT. This paper presents the Hydrological Safety Index (HSI) for the potential decamillenarian flows, obtained from the historical series of updated daily average flows, from 14 Hydroelectric Power Plants (HPPs) of the Brazilian federal dispatching agency National System Operator (ONS) and refers to the average of the daily natural flows until 2015. The data was divided into two samples for each HPP: the first corresponding to the updated series (or total), and the second, to the series up to a year before the start of HPP construction (or partial), when theoretically the detailed design should be completely defined. The Pivot Table method, developed within the scope of this research, provides the series of maximum annual natural flow of each sample. The Gumbel statistical method determines the decamillenarian flows, allowing the evaluation of the impact caused by the increase of the maximum annual flows since beginning of the series. The index is defined by the ratio between total series x partial series. In the 1980s there was an increase in the HSI that corroborates a non-stationary hypothesis. Finally, it was observed that in 93% of the analyzed cases the HSIs were greater than 1.00 and, therefore, it should be subject to hydrological reanalysis. To increase the knowledge and to help decisions, the results indicated that Brazil must build a single database with the official series of natural flows available, validated by the various agents responsible for the Brazilian water resources management (ANA, ANEEL, ONS, CPRM, etc.). In addition, it is necessary a periodical reassessment of all these spillways, as recommended by Federal Law # 12334 of September 20th, 2010, in order to verify the safety of these structures.

ABSTRACT. The decision to adopt the Slope Layered Method for Roller Compacted Concrete (RCC) placement as a construction methodology for the Power Intake, Central and Side Walls Structures focused in the reduction of the construction period time of Belo Monte HPP. This technology allows the gradual forms lifting whenever the concrete sub layers placement reaches the total layer height, reducing the time gap between two consecutive layers placement. In the horizontal layers placement methodology, the forms rise up in a single step, after the placement completion of the whole layer, causing a longer time gap between placements of two consecutive layers. The RCC structure extends from the variable elevations of the rock foundation to the 60.50 m elevation, just below the sill, includes Power Intake, Central and Side Walls structures of Belo Monte HPP and comprises a total volume of 687,964.14 cubic meters, that corresponds to about 20% of the total undertaking concrete structures volume. This article presents the foundation profile, the project layout and construction methodology in accordance with the best RCC current execution practices.

ABSTRACT. The modulus of elasticity and stress-strain behavior of concrete has typically been assumed to be similar for both compression and tension. It has also been typically assumed that a single value for modulus of elasticity will accurately describe the stress-stain relationship throughout the entire range of stresses from zero to ultimate load. Further, it is also typically assumed that the stress-strain behavior and tensile strain capacity is the same in both the horizontal and vertical directions. Although these assumptions are common practice and are described by somewhat similar formulas in various codes, the assumptions can be quite erroneous, resulting in inaccurate assessments of stresses, strain capacity, and cracking in concrete.

This paper summarizes published and unpublished efforts over the past 25+ years, substantially with Roller Compacted Concrete (RCC), demonstrating that site specific testing is necessary in order to establish the real behavior and correct values to use in stress and strain (cracking) analyses. This is much more important for unreinforced mass concrete than for reinforced concrete where embedded steel is the primary controller of cracking behavior. The paper emphasizes caution with regard to applying the results of tests on one project using one mix or family of mixes with one aggregate to draw conclusions on behavior at other projects. In fact, one of the authors (Schrader) has published information based on data that was accurate for one project, but later found to be non-applicable to other projects, perhaps leading to some unintended misuse.

The accumulation of global data in the paper demonstrates that, especially for lower strength concretes and RCC (even at higher strength), the stress-strain behavior of concrete is often very non-linear, and that it may be notably different (or somewhat similar) for tension vs. compression. Results of most standard test procedures for modulus that only test under compressive load and only establish one value for modulus based on only two points of the stress-strain curve, typically at about 10% and 40% of ultimate load) is often very misleading.

ABSTRACT. Roller compacted concrete (RCC) represents a great advance in dam construction. The technique consolidated the reduction of time for great constructions, even with large volumes of concrete placed. In addition, with the significant reduction in cement content, it is possible to control the thermal cracking and reduce the occurrence of alkali-aggregate reaction, considering, also, a better economic benefit when compared to constructions with normal concrete. The advantages of RCC allowed the construction of 205 Brazilian dams in the last 40 years, in accordance with the most recent data collection of RCC dams, what is presented in this paper. It is estimated the construction of 660 dams of RCC all over the world. Considering the importance of RCC technique in great constructions, it is essential to have documents that prescribe instructions for control and production of this type of concrete. In Brazil, in 2014, three parts of the NBR 16312 Standard about RCC were published, which included topics on terminology, laboratory tests and field tests. The topic about field control is discussed in Part 4 of the aforementioned Standard. The continuous improvement in methods of RCC production is essential to ensure the technique success and the structure durability regarding to the required purpose. Thus, methods of control and parameters for approval of field material in recent constructions in Brazil are presented in this paper, in order to update the community about the procedures that have been applied and to present the innovations established in the development of this practice.

ABSTRACT. The internal attack by sulfates in concrete is basically characterized by the formation of deleterious byproducts, such as delayed ettringite formation, which occur due to the presence of the sulfur element (S) in its chemical structure. The byproducts have expansive properties, which, after the cure of the concrete, enhance the occurrence of internal strains, promoting crack propagation, mass loss, decrease of mechanical resistance and durability of the structure. Although the subject is currently studied, there is little research related to data optimization and statistical study of the morphology and size of these byproducts. This article describes the adaptation of the hierarchical analysis to attribute statistical weights in the qualitative results obtained by the scanning electron microscope (SEM). To obtain the main objective of this research, roller-compacted concrete was extracted with possible occurrence of internal sulfate attack in a dam located in the state of Paraná, in southern Brazil. Then, the samples were mapped in laboratory and observed the presence of gypsum, in addition, measurements of the size of the ettringite were carried out with SEM-FEG/EDX and qualitative and semi-quantitative chemical microanalyses by dispersive energy spectroscopy, EDX. The adaptation of the hierarchical analysis to attribute statistic weights proved to be an option for the transformation of the qualitative data of the ettringites observed in the SEM-FEG.

ABSTRACT. Shortly following the award of a Contract that included a large RCC dam, on mobilization to the site it was realized by the stake holders that the use of fly ash was prohibited, as recent legislation had banned import and transport of fly ash in Jordan. The ban has been imposed due to environmental concerns. The project needed to come up with a suitable replacement for fly ash that was not only cost effective but also met the project design construction conditions, including temperatures exceeding 35-degrees Centigrade for most of the year. The RCC mix design was also required to meet other design criteria such as strength and water tightness. This paper presents the structured program implemented to arrive at the most suitable RCC mix design. RCC dam construction on the project has commenced.

ABSTRACT. Due to the evolution of knowledge on the estimation of maximum flood flow, in addition to more complete data records and even the alteration of the characteristics of catchments, some of the dams currently in operation, specially the older ones, do not have the capacity to safely convey their peak design flow without the occurrence of overtopping. The solution to this problem can be either the construction of an emergency spillway, raising the top of the dam, lowering the maximum water level or some combination of these solutions. The solution of a new emergency spillway is costly, particularly in the case of small dams, where the entities responsible for the dam administration usually have scarce financial resources. As an alternative to the conventional approaches, the application of roller compacted concrete (RCC) overlays is an expeditious technique which, among other advantages, does not require emptying the reservoir. For these reasons, the application of RCC overlays presents itself as a technically and economically interesting solution. This paper presents a brief overview of the application and performance of RCC emergency spillways, discussing its advantages and shortcomings. To illustrate the application of this technique, an emergency spillway for Arroio dam, a small earth dam with an insufficient flow capacity, is presented and the cost of this solution is compared with the actual cost of a traditional labyrinth spillway.