ABSTRACT. Some of Electricité De France (EDF) dams are affected by internal swelling reactions (ISR). The process to manage these structures is first to collect data on all the phenomena, such as swelling, shrinkage, creep that are developing in the concrete thanks to in situ monitoring, cracking visual reports and laboratory testing. Then, a dedicated concrete behaviour law implemented in the finite element software Code_Aster reproduces the displacements, the cracks and the stresses developed in the dam up to the present days. The aim of that kind of model is double : to calculate the dam stability for the next decades and, eventually, to simulate different kinds of rehabilitation in order to choose the better one in terms of cost and effects. The aims of this paper is to describe the principal equations of the model and to show an application on a real french dam. The model is able to reproduce the behaviour of the concrete affected by alkali-aggregate reaction (AAR) or delayed ettringite formation (DEF) thanks to anisotropic plastic strains coupled with the damage theory. The poromechanical framework, used to develop the model, strongly links the ISR swelling with the creep. It takes into account some environmental characteristics (the water saturation degree, the temperature) and multi-axial external loadings (a swelling anisotropy can be produced). Furthermore, it differentiates the ISR diffuse micro-cracking which provoke the decrease of mechanical characteristic (strengths and elastic modulus) and the macro cracks mainly induced by swelling gradients which can lead to a loss of the structure monolithic. The second part of the paper is an application of the model to a French dam: from the modelling to the rehabilitation.

ABSTRACT. The hydroelectric Cambambe is located in the middle section of the Kwanza River, the main Angolan river, about 180 kilometers from the capital Luanda. The dam was built in the 60’s by SONEFE (National Society for the Study and Overseas Business Finance) with detailed hydraulic studies by LNEC (National Civil Engineering Laboratory) in Lisbon. The arrangement of the main structures consisted in a 70 m high and 340 m long concrete dam with double curvature arch-type containing a 100 m long broad crest type spillway in the dam’s body and an existing generation circuit. The Cambambe Hydropower started its operation in 1964. In 2004, after 40 years of operation the power plant owner ENE (Nacional Enterprise of Energy) decided for carrying out the works of rehabilitation and expansion. The rehabilitation project comprised in change of the installed capacity of 180 MW to 260 MW, subject to the raising of reservoir level. On the other hand, the expansion project consisted in the heightening of 20 m of the existing dam, the construction of two new spillways and the building of a new generation circuit with a new powerhouse, with an installed capacity of 700 MW. Finally, this project increased the installed capacity from 180 MW to 960 MW, doubling the Angola’s generation capacity.

During the project, there were some issues as the erosion caused by cavitation in the existing bottom outlet, the occurrence of floods during the dam heightening and difficulties to protect the powerhouse construction due the river’s narrowness. Thus, this paper describes the design development and how the abovementioned challenges were overcome to accomplish the Cambambe Dam Hydropower project, which the construction was concluded successfully in 2016.

ABSTRACT. Camará dam is a Brazilian 50 m high roller compacted concrete structure founded on granite and migmatites with expressive weathered exfoliation joints, which develop parallel to the topography. In 2004 the left abutment foundation failed due to the presence of such exfoliation joints, which caused the dam to collapse, emptying the reservoir. The rebuilding process started in 2011 and the new geomechanical model came up with a set of joints, parallel to the surface and some faults with a high degree of weathering producing a soft material that retains rock mass relics. To a certain depth the presence of those features compromises the sliding stability of the dam, since the available friction angle for the discontinuities was taken as 35º, with no cohesion. These parameters are insufficient to fulfil the design criteria requirements, As a consequence, concrete surface shear keys were needed downstream of all concrete blocks.

This paper presents the main characteristics of the dam foundations as well as the treatment criteria and procedures for refurbishing the left bank blocks, spillway and part of the right bank. Instrumentation for monitoring the dam behavior is considered in this paper, as well.

ABSTRACT. The total concrete volume of the Belo Monte hydropowerplant is 2.847.720 m3. In order to minimize the probability of occurrence of thermal cracking as well as to avoid the eventual formation of delayed ettringite formation, maximum temperatures of fresh concrete were specified in the several concrete structures of the project. This paper presents an evaluation of the thermal behavior of the concrete structure of the intake of Belo Monte HPP during its construction and compares the temperatures measured by installed thermometers and the calculated theoretical temperatures. Theoretical temperatures and derived stresses were calculated using a three dimensional finite element method software. Thermal stresses analysis considered several parameters such as the constructive methodology, thermal and mechanical properties of concrete, type of curing and formwork, heat of hydration of cement, adiabatic temperature rise of concrete and local environmental conditions. The thermal analysis was fundamental to define the concreting plan. Derived from the calculated temperatures the resulting thermal stresses were important to fix the concrete cooling plan to be adopted and to reduce the risk of thermal cracking.

ABSTRACT. The aim of the present work is to present a computational code in FORTRAN, based on the Finite Element Method, capable of simulating the thermal behavior of a two dimensional medium subjected to conduction heat transfer. The code is used to develop a numerical model of the buttress dam of the ITAIPU Hydroelectric Power Station (CHI). Thermo-structural coupling is performed using the temperature field as the nodal contour condition via the initial thermal deformation. In order to validate the model, the ANSYS® commercial software is used, the efficiency of which is proven in the technical literature, and the thermo-structural coupling of which is performed with the tools available in the Workbench. Finally, the results of the proposed coupling model are compared with the dam instrumentation data.

ABSTRACT. This paper presents the most relevant information regarding preliminary studies, field and laboratory tests, and executive project for rehabilitation of Guaricana Dam, that belongs to the Guaricana Hydroelectric Power Plant. Guaricana Dam has 29.50 m of maximum highness and is 95.50 m long, was built in conventional concrete and is a relatively old dam. Its construction was finished in 1957. The dam foundation consists on a good quality gneiss. The dam rehabilitation design included the execution of two curtains. The first one is an injection curtain, divided on primary, secondary and tertiary grouting holes. The second one consists on a line of drain holes. Both curtains were carried out in the dam concrete body and its foundation. In addition, injection grouting was carried out through packers in faces and drainage gallery of the dam. Investigations through holes, as permeability and physical-mechanical tests, were performed to characterize the hydromechanical properties of the dam concrete and foundation. Alkaliaggregate tests were performed on aggregates sampled from the dam drill cores. The results allowed to define the materials of the grout to be used in the grout curtain and in the injection packers. Stability and percolation analyses were performed to evaluate the safety conditions of dam in three conditions: a) before, b) during and c) after rehabilitation work. Stress-strain analyses were also performed in order to subsidize the decision about the pressure level to be applied during the grouting work under safe condition.

ABSTRACT. One of the most important best practices of dam engineering is the safety assessment of existing dams that were built in a period when there were no well-established guidelines and previous experience was the key factor. The assessment usually indicates the need for structural adaptations such as heightening and reinforcement. The article will present the post-tension rehabilitation of the spillway at the Salto Paraopeba Hydropower Plant (HPP), located in the city of Jeceaba – MG, Brazil. The rehabilitation was part of the project to increase the plant’s installed capacity. The dam is a concrete structure with a free overfall spillway. It is 27m high and has a total crest length of 76m. The spillway is composed of 7 blocks, separated by contraction joints. It is important to mention that the discharge capacity is lower than that determined by current project guidelines. During periods of high flows, debris accumulated in the spillway opening and pillars of the gate lifting mechanisms, primarily due to the existence of a pedestrian overpass. A stability analysis was initially carried out, concluding that the structure does not meet the current project guidelines for the exceptional load case regarding overturning. The first stage of the rehabilitation, concluded in 2016, consisted of the controlled demolition of the pedestrian overpass and pillars over the spillway crest, without river diversion. The second stage, structural reinforcement, began in 2017 and comprises the post-tensioning of the RB190 (low relaxation) 15.2mm-wide strands along the spillway crest. The post-tension load was distributed by means of a blockout for each block, embedded in the crest and situated 1.5m from the spillway’s upstream face, perpendicular to the foundation surface. The load per anchor was 147.7tf/m in 12 strands, ranging from 2 to 8 anchors per block. The rehabilitation improved the safety and operational condition of the spillway, in turn meeting current project guidelines.

ABSTRACT. The paper regards the Dam’s Rehabilitation and Modernization of Monitoring Systems in Drini River Cascade. This Cascade is unique in Europe in regard to the dam types and their heights, the artificial lakes created, the installed power of the HPPs and their Operational Management.

Drini River is the longest river of the Albania with a length of 160 km. The drini river bed in northern Albania has been transformed into a chain of 3 artificial lakes with total water capacity of 3.4 billion m3 which supply water to the three largest Hydropower plants (HEPP-s) of our country. The HEPP-s of Fierza, Koman and Vau I Dejes are built on the Drini river bed in period 1971 to 1986. Their installed capacity is 1350 MW and their average energy production is 4 000 GWh per year.

During 4 last years, KESH sh.a has invested more than 70 million Euro in improving the physical condition of assets and technology in order to guarantee the dams safety, to increase production efficiency and to improve working conditions in order to achieve the highest standards of hydro power production and trading activities.

This paper summarizes the performed measures regarding the Dam’s Rehabilitation and Modernization of Monitoring systems on 5 dams of Drini Cascade during last 4 years and it is intended to evidencing the advantages of Dam’s monitoring in terms of their life and improvement of water basin integrated management.

The Dam’s Rehabilitation consist in rehabilitation of downstream area of dams regarding of the damages during the discharges of spillways and land erosion in this areas; rehabilitation of dam crests and down part of them; Land protection from erosions and discharges; reservoirs protection from sediments; maintenance and rehabilitation of spillways radial gates.

The Modernization of Monitoring Systems consist in Installation and Automatization of Seismic monitoring systems; Hydrological, meteorological and geodetic monitoring systems; Monitoring systems for measurement of underground water level and leakage.

ABSTRACT. Gravity dams are usually built with mass concrete, which has a large volume of concrete. During the process of hydration of the cement particles, there is release of heat, in a process called heat of hydration, raising internally the temperature of the concrete. This phenomenon causes the internal temperature of the concrete to be different from the surface temperature, resulting in a thermal gradient, in addition to a slow cooling in the core of the dams. These temperature changes give rise to thermal stresses, which, if not foreseen and prevented can cause damage to the structures when they exceed the resistive capacity of the concrete. The thermal stresses take into account the phenomenon of intrinsic creep in the concrete, that is, there is variation of the modulus of elasticity over time with the change in temperature. There are a few techniques to try to minimize this problem, such as layered construction, concrete released at lower temperatures, the use of low heat of cement hydration, among others. An effective way of preventing thermal problems in dams is the numerical simulation, being possible with the mechanism, to predict the most critical regions and to analyze, then the probability of structural damage. Thus, this work shows numerical simulations using the finite element method - MEF, through the ANSYS program, for layered gravitational dams. This article tries to expose some of the most favorable conditions in the construction process, identifying possible cracking sites, through numerical and analytical analyzes, contributing to the dissemination of these studies and showing community interest, constructive methods and methods of analysis that can induce more construction.

ABSTRACT. The risk-based approach to dam safety that emerged in the 1990’s underwent a transition to risk-informed dam safety in the 2000’s but agreement on what constitutes risk informed dam safety and how it differs from risk-based dam safety has not yet emerged. Development of a framework requires consideration of the emerging need to re-examine the foundations of risk analysis methods and address weaknesses in various aspects the methodology that have emerged over the past 25 years. Of these weaknesses, the matters of failure within the design envelope and the comprehensiveness of existing methods are dealt with in some detail in the paper. A feature of contemporary risk approaches to dam safety that requires re-examination is the matter of failure modes analysis as failure modes might be described differently in different practices. A second feature of contemporary risk approaches is the use of case histories of dam failures and incidents as a platform to build basis for the safety analysis. A rationale to abandon this approach and focus on operational functionality of the dam and reservoir as a system as a starting point is presented. Failure modes can be derived from the operational modes. The use of functional analysis diagrams to represent the model of the way the dam functions as a system to deliver its products and services is presented in the context of the determination of the failure modes of a spillway gate sub-system. Another aspect of dam safety assessment that requires reconsideration is consideration of the “inflow flood” as a hazard, and specification of the hydraulic capacity of spillways in terms of an “inflow design flood”. Floods are considered as hazards to dam safety in the same way as earthquakes are considered. However, the inflow acts on the reservoir behind the dam whereas the earthquake is applied directly to the dam (and to the reservoir), making the flood hazard distinctly different to the earthquake hazard. Given that the dam is constructed to capture floods for the benefit of producing products and services, the inflows are part of the overall functionality of the system and when viewed in this way should not be considered in the same context as earthquakes and other natural hazards.

ABSTRACT. Likewise other building structures, dams are subject to uncertainties during their commissioning. However, dam breaks are commonly catastrophic, destroying entire villages and devastating biodiversity in the region. Therefore, it is necessary an efficient risk management of dams, taking into consideration the probability of a collapse to occur and the probable consequences in case of a disaster. In Brazilian scenario, for instance, the Dam Safety Policy plays an important role as a guideline for risk management in dams. Saying that, in order to investigate the occurrence of a dam break it is necessary to verify the probable causes of the incident, such as slope instability, overtopping or piping. Also, the breach dimensions and hydrograph are important inputs for the flooding modelling. Once having the inundation boundaries, it is necessary to map the most dangerous areas (based on the product of depth and flood velocity, which represents the level of hazard of the flood) and the arrival time of the flood. All this study is necessary for the elaboration of the Emergency Plan, which must be done by dam’s owner, according to Brazilian law. So, this paper presents a methodology to simulate the flood provoked by a dam break and, to fulfill this goal, it was conducted a hypothetical simulation of the dam break of the Carpina Dam, located in the state of Pernambuco, Brazil, generating a flood in the Capibaribe River until its mouth in the city of Recife. The flood was simulated in a full 2D model using the software HEC-RAS®. As a result, it can be noticed large areas with red alert, where buildings can collapse due to water power. Furthermore, the use of a less precise Digital Elevation Model (DEM) tends to increase flood area and distort results nearby the downstream face of the dam, in a region with a supercritical flow regime, producing higher flooding depths compared to other simulations with more precise Digital Elevation Models. Regarding to the breach dimensions, the Froehlich (2008) equations were chosen, as long as they provided more realistic results for peak flow and breach development time. However, it is necessary to update such equations using the analysis of recent dam break cases.

ABSTRACT. In the study of critical events such as dam collapses or extreme storms, mapping of downstream valley floodplains is essential for a quantitative and qualitative analysis of social, economic and environmental impacts over the affected regions. Mapping is important for a realist conception of the Emergency Action Plans by the entrepreneurs and public authorities, in order to allow warning, rescue and, consequently, protection of the lives. Based on a mathematical modeling of the hydrodynamic flow of the Paranapanema River cascade, located on the border between the States of Sao Paulo and Parana, in a Geographic Information System (GIS), this article compares the results of flooded areas, in specific regions, generated based on two digital models, with different representations of the riverbanks, one of surface (DSM) and another of elevation (DEM). Therefore, a reach of the Paranapanema River was chosen, which comprised a significant floodplain area, allowing the identification of the differences between the mapped impacted areas generated with DSM and DEM models. The floodplain areas obtained were later compared to satellite images from the same hydrological event, allowing the evaluation of the reliability of the simulations and their results, obtained by the use of both techniques. Furthermore, the article aims to discuss the use of DSM or DEM as a base for mapping flooded areas through a critical analysis of the difference between the generated contours and its relevance in the downstream valleys risks evaluation.

ABSTRACT. This paper proposes a fuzzy methodology for dam failure risk assessment, having developed a case study with the Simplicio hydroelectric power plant located in the Center Western region of Brazil. The fuzzy inference was obtained by calculating the Critically Index in a first step, and then the defuzzified Risk Priority Number in a second step. Through a FMECA there were introduced estimates of failures in the plant related to the overtopping, mass movement of the gravity concrete dam (global instability), excessive deformation and blocking access of the crest, backrest instability caused by material movement, piping through the dam, water contamination, rapid lowering of the reservoir and foundation failure. The most relevant issue with a moderate magnitude detected by the traditional FMECA approach is the piping erosion (concealed internal erosion) caused by the excessive seepage due to insufficient or inadequate foundation, which may due to the improper design or construction. The fuzzy expert system, on the other hand, classified the risk magnitude as critical, caused by the high severity of the damage that might be caused by the piping erosion. The impact might cause several casualties, catastrophic and irreversible damage to the environment and a massive economic loss exceeding $100M. Moreover, the detectability is low, because the operation is not likely to detect the cause. Such result has practical consequences, because increasing the technical concern regarding the foundation stability would result in a more frequent inspection schedule and an enhancement in the detection capability under the consideration of the As-Low-As-Reasonably-Practicable (ALARP) operational procedure.

ABSTRACT. Given the relevance and complexity of performing dam rupture modeling, there is a tendency to improve the computational tools available for this purpose, especially aiming to improve the calculation processes and to reduce simulation time. Therefore, this paper reviews the technical literature in order to identify the main software available for the hydrodynamic modeling applied to hypothetical dam break. To do so, a comparative analysis is performed between three software with worldwide use, based on the criteria of modeling capacity of floods induced by dam break, integration with geographic information systems (GIS), need for initial investment, computing time, post-processing resources and ease of use. In addition, as a case study, the MIKE FLOOD commercial software was selected to study the concrete dam break of Tucuruí Hydroelectric Power Plant, in the Brazilian Amazon. The results of the research show that choosing the computational tool depends on the availability of topo-bathymetric and hydrological data for the analyzed site. It is also noted that all the computational tools analyzed have good flood modeling capacity and dependence on the integration with GIS, and differ mainly in the need for initial investment, computing time, and post-processing resources. In a specific analysis, models that perform the coupled modeling (one and two-dimensional), such as the commercial software MIKE FLOOD, are presented as tools of maximum efficiency and good applicability in studies pertinent to the featured topic. Thus, it is observed that choosing the computational tool little affects the effectiveness of the research, but it directly influences the quality of the presentation of results, the time taken to prepare the design and the costs related to it.

ABSTRACT. The Brazilian Federal Law, 12,334/2010, establishes the National Dam Safety Policy that implies in the development of intelligent systems to monitor downstream valleys’ risk. Mapping possible flooded areas for different scenarios of extreme rainfall events or operational conditions like accidents require the use of Geographic Information System (GIS) to understand the associated risks of these occurrences. Those multiple scenarios are generated and obtained after an integrated risk management methodology and can become very complex when considering several structures along the river valley forming a dam cascade. In order to focus on those complexity, a new risk management method based on the use of GIS tools for the quantification of population, income and density, as well as the extensions of agricultural and environmental protected areas associated to the probability of flooding was developed and tested. The results are displayed through active thematic maps published on a web platform and accessible to the entrepreneur and civil defense agencies. The platform can be consulted relative to several attributes to mitigate risk. The maps demonstrate which populations, infrastructures, public services, among others, are most vulnerable to flooding. They also indicate water depth and the time that sites are likely to remain flooded, therefore permitting the calculation of socioeconomic and environmental damage after occurrence. Tests were carried out in the cascade of eight dams along the 500 km Paranapanema River, on the border between the States of São Paulo and Paraná, Brazil, where approximately 55,000 inhabitants live in a region whose economy is based upon agricultural production, among twelve environmental preservation areas. Maps and facilities obtained are discussed. Thus, the new methodology based on GIS presented and the results for case study form an essential subsidy to risk management associated with dams and flood management.

ABSTRACT. The Brazilian legislation requires the elaboration of the Emergency Action Plan (EAP) for dams considering the risk category and the potential damage associated with the project. In the EAP, the Self-Rescue Zone (SRZ), which is the impacted region of the downstream valley of the dam bounded by the distance corresponding to a flood wave with an arrival time of thirty minutes or 10Km must be defined. Another criteria for the classification of the impacted area by dam breaks or even the propagation of exceptional floods may lead to a more detailed representation of impacts, such as the hydrodynamic risk, identified by the relationship between depth and velocity. This article aims to present and discuss updated methods for evaluate and zoning the impacted areas in the downstream valley. Since different dams have different characteristics such as height, dyke width and stored volume and considering that these magnitudes are directly related to the length of the affected river reach as well as the flood wave travel time resulting in a very, the most appropriate method to map downstream impacts of the dams can widely vary. In the present study a comparison of impact mapping results along Rio Paranapanema, Sao Paulo, Brazil, constructed for zones with different geometric characteristics is presented in order to analyze the accuracy and relevance of the resulting information in the formulation of emergency action plans.

ABSTRACT. Although Dam failure is a rare event, it is associated with catastrophic impacts on communities, including loss of life. The National Policy on Dams Security (PNSB), enacted in 2010, lists as one of its objectives the promotion of a culture of dam safety and risk management. It also presents, as one of its instruments, the Dam Safety Plan. This plan includes in its contents the Emergency Action Plan (PAE), which guides decision making in emergency situations. However, there is a gap regarding the response time and reliability of the actions of the PAE that can be minimized through the use of risk analysis techniques. Currently is being debated in the Brazilian Senate the law project nº 224, which modifies the PNSB and proposes, in its article 17, the assignment to the entrepreneur of the contracting of insurance or presentation of financial guarantee in the case of dams of high category of risk and potential damage. If approved, this new law will grant a term of 02 (two) years for the adequacy of the entrepreneurs to the insurers. This paper assesses the future demands that will arise for insurance brokers, the adaptations that entrepreneurs must make in their processes of management and monitoring of dam safety, as well as describes how risk analysis techniques may be an important tool to enable better negotiation of insurance policies.

ABSTRACT. The risk quantification is part of a demanding task in the safety assessment of dams, and it is important to anticipate the diagnosis of accidents due to fails in the field of geotechnical engineering of dams. This paper is focused in piping and slope deformation anomalies in the embankments, the most frequent ones, according to security reports presented by the local and national agencies of the Ceará State, as a part of their security protocol. The use of probability functions to represent the fails according to aging or geotechnical particular aspects is an alternative way to establish the risk quantification. A methodology for a quantitative risk assessment (QRA) is presented, using the concept of the reliability applied to the Weibull distribution. Dams classified as in high risk due to severe anomalies presented in the formal inspections are chosen as case study to validation of the results presented by the probabilities analysis. In the three cases of Premuoca, Forquilha and Acaraú Mirim, the method presents proper to the anomalies assessed.

ABSTRACT. Huge losses in both human lives and economic properties can be resulted from an embankment dam failure, which represents 75% of the world’s dams. Therefore, dam-break modeling is of great significance for dam failure damage assessment, risk analysis, disaster control and mitigation. The task of evaluating a dam-break scenario usually requires determining breach formation, outflow hydrograph and flood routing, involving a great number of variables and uncertainties. Due to the increasingly powerful computers for processing these large data, many breach models have arisen over the years. One of the most known models is BREACH developed by Fread in 1988 at the National Weather Service for embankment dams submitted to either piping or overtopping. This is a free and open-source model written in Fortran that provides the outflow hydrograph and is capable of simulating a dam with two different materials: inner and outer core materials. However, the approach consists on averaging both of them and thus homogenizing the materials, consisting in a major simplification that impacts dam-break predictions. Nowadays, very few models have advanced on this aspect of modeling the structure, none of them being open-source and of free use. Therefore, this paper presents a new feature to the NWS BREACH allowing the user to define zones of different materials (e.g. incorporated cofferdam) more freely, thus resembling better real-life dams and predicting more precisely the outflow’s hydrograph. This new feature is suitable to overtopping cases only. The case studies of Teton Dam in USA and the landslide dam on Mantaro river in Peru, which validated the original model, were used with the new function. In all simulations, the D50, D90/D30 and cofferdam’s height were altered for a sensibility analysis and a final run was made with data from typical cofferdams build in Brazil. The results presented a good and expected behavior, reducing the peak outflow, breach’s dimension and time to peak. For typical cofferdams in Brazil that were modeled, the peak outflow was reduced around 20% and the breach’s dimension around 30% in some cases.

ABSTRACT. Infrared thermography (IRT) is a non-destructive testing method, which allows the examination or inspection of part of material or system without impairing the future usefulness, and it is applied to “see the unseen”. IRT uses the distribution of surface temperatures (thermograms) to assess the structure or behaviour of what is under the surface of an element without any contact. IRT has a large information potential and a wide field of application, because it is a testing technique that can assess large area and can be operated as an indicating method, giving either qualitative or quantitative data. Nowadays, thermographic method has proved to be an effective and economic tool, very valuable in several branches of engineering, namely in structural engineering. It can detect internal voids, delaminations, and cracks in concrete and masonry structures such as bridge decks, dams, and building envelopes. The Covão do Ferro dam, a masonry gravity dam, located at high elevation on Estrela Mountains, Portugal, with a maximum height of 32.5 m and a total length of about 400 m, was rehabilitated between 2004 and 2006 in order to waterproof the dam’s body and improve the structural stability. The main works included the injection of cement grout into the dam body and the rock mass foundation, the installation of a PVC membrane on the upstream face, and the strengthening of the drainage system through the opening of new drains. Eleven years after this rehabilitation, IRT was used to analyse the waterproofing membrane state of conservation and mainly the eventual detection of anomalies in its surface. For this, several themograms were obtained during two days, in a period of low level of water in the reservoir. This paper shows the potential of IRT on the assessment of the waterproofing membrane state of conservation, providing important information for a more detailed inspection.

ABSTRACT. The data collected from the concrete dams monitoring systems is always constituted by physical quantities, scalar or vector, acquired with different measurement instruments dispersed inside the structures in a discrete number of points previously selected. For the interpretation of observed behaviour as well as for the control of the dam’s safety it is often necessary to know in more detail the distribution of these quantities inside the bodies of the structures and the interpolation is the most suited method to estimate and represent the spatial distribution of these quantities in the entire domain under study.

In order to improve the knowledge about the distribution of these physical quantities, mainly with the purpose of providing the best possible data to the numerical models, a methodology of interpolation, based on the distances between points, was developed. The methodology ensures greater continuity to the spatial distribution of the quantities and also may take, or not, into account anisotropy in the spatial distribution of the physical quantities. The simplified hypotheses of the method are described, as well as the main calculation steps of the developed algorithm.

An application of the method to a case study in dams engineering, related to the interpolation of observed temperatures in a reduced number of thermometers and jointmeters to obtain data in all the nodes of a finite element mesh of a large arch dam is presented. The excellent results obtained allowed the direct use of the temperatures spread widely by this method in structural analysis to interpret the observed behaviour of the dam during the first filling of its reservoir.

ABSTRACT. This paper presents the methodology used for the modeling of the Joint Monitoring Index Blocks Response of the Dam (IMCRB) and the orientation for the decision-making about the stability of the process. This index encompass diverse characteristics of the behavior of a dam’s concrete blocks, adding information of the diverse measurement data provided by the extensive instrumentation contained in it allowing a more simplified way of interpretation of the results. Its elaboration is based on techniques of multivariate analysis, control charts, confidence intervals and time series. The methodology for the construction of the IMCRB follows a pattern of insertion, verification, standardization, when necessary, and the generation of a correlations matrix which will have its eigenvalues and eigenvectors calculated. To this matrix, it is applied the factor analysis which, when tested and validated, will define the number of factors and the respective scores used in the modeling of the IMCRB. Then, the stability of the time series is verified, proceeding to its correction, if needed, throughout differentiation, the limits of control and alert are defined, at 95% and 99% of confidence, respectively. Lastly, the validation is made throughout the insertion and correction of new data so it can have index values calculated which will contribute to the decision-making. Also, to exemplify the methodology, it was applied to the D20 block of Itaipu Dam’s instrumentation.

ABSTRACT. In plain or reinforced concrete structures the different cracks reflect the internal, mechanical and chemical, processes affecting the material. And it denotes an evolution of the material to adapt itself to the loading or environmental conditions at each stage of its service life. In massive concrete structures such as dams the cracks given by differential expansion may have economical consequences. For that reason a monitoring technique such as Digital Image Correlation (DIC), capable to catch those cracks in a wide region, is of great interest to prevent the consequences with an early diagnostic. Digital Image Correlation is a contactless and non-destructive monitoring technique, consisting on a set of photographs correlated with a reference to calculate the displacement field. In this paper, the methodology developed by Saucedo-Mora et al. (2017) is applied to correct the dataset and to obtain the cracking information in a specific region of the Itaipu Dam. If the crack tip is captured in the photograph, the measurement can include the fracture energy released by each crack, the mode of the failure and the cracks active in each measurement with its opening. This methodology allows the continuous measurement in a wide region obtaining information of the structure. Which can be used for a continuous automatic evaluation of the structural integrity, used for both: an identification of the weak regions in the full structure with a mapping, and the measurement of the material mechanisms failing. This information can be used to identify locally its more appropriate repair.

ABSTRACT. The Joint Monitoring Index Blocks Response of the Dam (IMCRB) was created by analysing the series of sensors for monitoring the displacements of structures and foundations, from two buttresses blocks in Excerpt D located in Itaipu’s dam, considering the action of the ambient temperature and the water level of the reservoir. This index contributes to the diagnosis of changes in the standard behaviour of the dam structure, and after its formulation was validated in this same section. In the following study, the IMCRB is reformulated and validated for the two blocks of Excerpts F and other two Excerpt I, the manual measurement data of the following tools: pendulum, ancillary bases, shaft extensometer and Piezometers acquired between January 1990 until November of 2017. The IMCRB reworking involved the using of statistical methods: factor analyses, analyses of series, confidence intervals, with a big participation in the modeling and the remaining set for index validation. The reworked Joint Monitoring Index Blocks Responses (IMCRB) of dam can help in the overall performance analyses of selected blocks concrete structures, preview its behavior and help in the anomalies data identification, felicitating in the decision making.

ABSTRACT. The Joint Monitoring Index Block Responses of the Dam (IMCRB), built with the statistics technique univariate and multivariate, to notice about overall behavior of blocks D38 D54 and D57, on stretch D of Itaipu Dam. The wrought of index, based on manual measurements gauged together next instrument: Piezometes, Pendulum, Bases of Extend and Extensometer over of environmental condition (Environmental Temperature, Surface Temperature of block, level of water on upstream water during period between January 1990 until November 2017. In the dates set grouped, realized the existence of blank elapsed of period that it hasn’t measurement. For complete this blanks, to used time series. It was statistics treated of data with software MATLAB and RStudio for building complete matrix of data, application on the factorial analysis and get IMCRB. The data set it was standardized and separated in two groups. The first used to modelling of index and generate control letters. While that second group was used for result validate. Concluded that IMCRB could be using on studied blocks, well control letters generated to prove that IMCRB describing of behavior and the date trend, it could to be utilizing on dam monitor

ABSTRACT. Forecasting slope failure time is one of the major goals for researchers interested in dam or slope safety. An accurate forecast of the slope failure time can prevent losses of human lives and minimize damages to the property, as the anticipation of failure occurrences may provide enough time for counteracts to be taken. The most common methods are power law based, mainly the Inverse Velocity method, that infer the failure time by crossing the inverse velocity curve with the x axis in a cartesian plane. The original version of this method, under the assumption of a linear inverse velocity trend, uses only two inverse velocity data points to determine the inverse velocity curve. Most recently, many papers infer these curves using linear or nonlinear regression. Both cases present two problems. First, surface displacement data collected in real situations commonly present noise, which is amplified when this data is transformed into inverse velocity, leading to forecast degradations. Second, these methods only provide point estimates. However, given the fact that failure time is a random variable, interval estimates are more representative, bringing information not only about the most probable failure time, but also concerning the forecast uncertainty. In this paper, to face the first problem we propose filtering the data by means of the Singular Spectrum Analysis, which is a relatively recent mathematical technique capable of reducing noise rates of a time series without generating delays. Furthermore, in order to confront the second problem, the generation of predictive intervals by stochastic simulation is proposed, as there is currently no analytical method to determine these intervals. Two landslide case studies are presented intending to validate the proposed methods, one using georadar data and another based on extensometer data.

ABSTRACT. The continuous monitoring of dam’s displacements plays a key role in the safety control that is based on the comparison between monitoring data (e.g. observed displacements by plumb lines, geodetic methods or, more recently, with GNSS, Global Navigation Satellite System) and results obtained by numerical models, usually 3D finite element models (3DFEM). In the case of Cabril dam, no plumb lines were installed in the central section. So, the displacements monitoring in this section is performed by geodetic methods that do not allow a continuous monitoring (only two observation campaigns per year). Therefore, the use of GNSS is particularly useful since it allows a continuous monitoring of the top of the central section’s displacement. Because Cabril dam presents cracking problems since the first filling, it is of utmost importance to continuously monitor several notable points, which include the point at the top of the central section. For this purpose, the present paper focuses on the validation of GNSS measurements in the Cabril dam using a 3DFEM in which the cracking is simulated using interface elements. The 3DFEM was calibrated using the displacements measured with plumb lines (at two non-central sections) and measured with classical geodetic methods, considering hydrostatic pressure variations and seasonal temperature changes. The histories of measured displacements were analyzed using a statistical model of the type HST (Hydrostatic, Seasonal and Time effects) for effects separation, in order to facilitate the comparison between the measured displacements and the 3DFEM results. So, the 3DFEM was firstly calibrated using data from geodesy and plumb lines and then it was used to validate the GNSS measurements at the top of central section.

ABSTRACT. In 2016, permanent observation of GNSS (Global Navigation Satellite System) precision baselines was introduced in four Portuguese large concrete dams, in order to monitor horizontal displacements. The results presented in the paper show that there is a great potential for the application of GNSS technology in dam monitoring systems. The paper describes the filtering strategy used to process the observations in order to achieve the millimeter accuracy level as well as a Bayesian procedure developed to automatically identify and eliminate of outliers and gross errors. Finally, the benefits of such techniques, including the potential of the GNSS in the domain of dam displacement real-time monitoring, are described.

ABSTRACT. Dams and the associated reservoirs are potential risk factors as they can lead to serious accidents that endanger the safety of people and property in the downstream valleys.

So, each dam introduces into the downstream valley an uncertainty factor related to the possibility, even if remote, the cause of floods with extremely serious consequences.

Some of the most important accidents caused by dams failures in the past (Vega de Terra - Spain, 1959, Malpasset - France, 1959, Vajont - Italy, 1963, Teton - USA, 1979, Tous - Spain, 1982) made it necessary to reflect on the risk in the downstream valleys and in the prevention against the potential effects of these accidents.

Since the 1960s, dam safety regulations and procedures have emerged, involving explicitly the effects on the downstream valleys and prevention against the potential effects of accidents, including early warning systems and populations evacuation plans.

Currently, the media and public opinion as well as accountability for damage resulting from a possible accident are very strong pressure factors that have made the safety of the valleys downstream of dams an emerging domain of public interest.

The actual Portuguese Regulation on Dam Safety has a special focus on civil protection measures and forces dam owners to implement Emergency Action Plans. The safety and risk management of dams has always been one of EDP Produção main concerns, being a reference in this subject. So EDP Produção promoted the realization of Emergency Action Plans of its dams.

In Spain the management of dam emergency situations was legislated in 1996 which led EDP Spain to start the process previously.

The present paper presents the evolution of Emergency Plans in EDP Produção and EDP Spain, revealing the difficulties and challenges related to the geographic dispersion of the dams, the involvement of several stakeholders, the complex approval process, the use of new technologies and, finally, the communication sessions to downstream valley resident population.

The last issue, that addresses the presents the trends emerging in the management of dam emergencies and that may impact on the implementation of future Emergency Action Plans in EDP Produção, is detailed in the paper.

ABSTRACT. Emergency Action Plans (EAP´s) play a key role in the overall Emergency Preparedness Planning of dams, particularly by defining the potential emergency conditions that may occur at the dam structures and by stating the actions and procedures to be carried out by the Dam Owners to minimize environment impacts, property damage and loss of life in the downstream valleys. Following the publication of Decree-Law 2007/344, which updated the main Dam Safety Regulations in Portugal, an increased attention has been given by the different Dam Safety stakeholders for the need to prepare, upgrade and implement Emergency Action Plans to the Class I (high consequence) dams. In spite of all the information available about this subject from different sources, the variety of topics included in the preparation of the EAP documents and the interrelation to be reached between the different players before, during and after an emergency occurrence, has in some situations introduced a level of unexpected complexity in a seemingly straightforward process. This paper aims to share with the technical community the recent experience of the Portuguese Dam Safety Authority dealing with the EAP´s, with a view to highlight a number of concerns related with its elaboration, evaluation and implementation.

ABSTRACT. This work presents the results of a software framework called PAEWEB (Web Emergency Action Plan) which is integrated into CEMIG's (which is one of the most solid and important groups in the electric energy segment in Brazil) corporate software and data environment. The PAEWEB automates the process of monitoring and assessing dams, but also covers the whole spectrum of the internal communication process regarding emergency maintenance and actions, taking into consideration that such actions must be in tune with CEMIG’s corporate Emergency Action Plan (a written document that establishes how to react during events). The primary goal of the PAEWEB is to monitor the various state variables (such as instruments readings, visual inspections, among others) regarding the dam state of operation. However, its intent is not only to provide valuable information regarding the dam operational state, but also to support users during emergency events. The way the PAEWEB achieve these goals is by both its user interface and the expert models that run underneath this interface. PAEWEB’s user interface (UI) was designed focusing mobile devices and it provides a rich chat-like interface with features such as picture, audio, video and location attachment that the users can interact during emergency events. Underneath, the PAEWEB counts with various expert models that perform online human-like evaluations, where the most notable ones are a fuzzy inference system that automatically detects any state variable that might be off its fuzzy limits and interacts with users through the UI by suggesting possible changes in the dam operational state signal (Leone-Filho, et al.), and a rule-based system with a semantic analyzer detects possible occurrences of words in the chats that might be related to actions described in CEMIG’s Emergency Action Plan that need to be carried out to mitigate the associated risks, and interacts with users through the UI. Thus, the PAEWEB is a system that might be used to monitor dams during crisis events, to help users to interact during crisis events, speeding up the communication process, and to monitor any sort of dam instruments whose reading might be uncertain and, sometimes, not meaningful.

ABSTRACT. Studies of dam failure simulations are crucial to the assessment of the dam safety and of downstream populations, for improvements of the damages mitigation through management and risk assessment process. Failures in the embankments can begins with a breach formation, that increase with the time evolution to a sort of evacuation channel over the dam. The outflow peak discharge and the flow hydrographs based on dam breach parameters are calculated through usual numerical methods. The resulting hydrographs and inundation mapping are important and required tools for the dam Emergency Action Plan (EAP), once they present the flood surface elevation and flow velocity in each time step at critical downstream locations. This study is applied to the Taquara dam inundation map, simulated an eventual collapse of the embankment dam due to a breach evolution, using two different approaches. It is analyzed the dam fracture formation parameters, considering the failure mode caused by piping and the breach modeling performed by empirical methods, assessing the fracture as a function of time and the hydrograph achieved from the breach outflow. With the data, the flood area map was defined and added to the EAP, mapping of downstream risk, predicting the water surface elevation and the available time to execute a potential evacuation of the valley population.

ABSTRACT. The Belo Monte HPP has been the largest engineering project executed in the Amazon and was considered a great challenge both in logistics and execution due to the large volumes involved in construction and the short period to execute them. In addition to the large volumes, the number of sites was appalling. As with construction planning, its technological control has also been the object of detailed planning. In terms of the laboratory, a central laboratory was built on the Belo Monte site, which is named Walton Pacelli de Andrade, in honor of this great Brazilian consultant of international renown and where tests of cement, steel, aggregates and concrete and geotechnical tests of compaction and complete characterization of soils, sands, drains, transitions and rockfill. Three more large laboratories in the sites of Pimental, which was named Ricardo Muzzi Guimarães, the first superintendent of Belo Monte Hydroelectric Plant, and in the Derivation Channel and Dikes. In addition, advanced labs have been set up at Dikes 6C, 8A, 13, 14C, 19B and 28 and at Road 27, to control the pavement. The complete laboratory team reached 340 people. It stands out in Belo Monte the implantation of AUTOLAB, technological tool developed for the Technological Control by the third author. In addition to the extensive laboratory team mobilized, the field control was done by a team of 80 inspectors, 90% of which was hired directly from the Federal Institute of Pará, in Altamira, where medium-level technicians were recruited, formed by that institute and developed by the construction experts. The Technological Control Management also included the installation and monitoring almost 2,000 instruments and the execution of 23,000m of drilling for the executive design development.

ABSTRACT. The Teles Pires Hydro Power Plant, located in the border between Mato Grosso and Pará states, has an installed capacity of 1.820 MW. Its operations took off in January 2015. The phase of the river diversion was executed through the construction of three tunnels measured 15 meters in diameter, on the left bank, built to handle an outflow of approximately 8.200 m³/s. The logistic previously defined for the closing of the tunnels and consequent phase of filling the Teles Pires reservoir was a critical stage, because of the marked seasonality of the Teles Pires River’s hydrograph, which used to define the activities order of this operation. The need to change the time to begin filling up the reservoir demanded the execution of alternative actions that would make feasible to close the tunnels, maintaining the safety during the operations as well as the outcome of the original project. Additionally, the diversion tunnels appropriate hydraulic behaviors during the flooding event occurred when operating, concurs to the project’s proof of premises and criteria adopted while measuring the structure. The following article presents some of the challenges faced during the final diversion closure period, the construction aspects and the structures conceptions and operations.

ABSTRACT. The Caculo Cabaça Hydropower Project in Angola, with a nominal capacity of 2 172 MW, is the third of seven steps of the cascade development in the middle Kwanza River, downstream Capanda and Laúca hydropower schemes. The scheme dominates a 112 663 km² watershed, with 587 m³/s average flow. The scheme includes a dam, two saddle dams, an underground waterway and power plant and an environmental flow power plant adjacent to the dam. The Caculo Cabaça dam is a 103 m-high RCC gravity dam with a crest length of 553 m, impounding a reservoir with a capacity of 436 x 106 m3 and an inundated area of 16.6 km2. The dam includes a frontal spillway located on the central blocks of the dam, controlled by five radial gates for a design flood of 10 020 m3/s and a double bottom outlet, for a maximum discharge of 1 348 m3/s, at full supply water level. The waterway system is designed for a water discharge of 1 100 m3/s. Four concrete-lined vertical pressure shafts with a diameter of 9 m lead the water from the reservoir to the underground power plant involving a drop of 190 m. The power plant, is equipped with four 530 MW Francis turbines coupled to a 590 MVA generator, operating at a nominal net head of 209 m. The cavern accommodating the power plant has the following dimensions: 26.5 m wide, 221 m long and 68 m high. Two pressurized tailrace tunnels, with a length of about 5 200 m and an unlined arch rectangle cross section, 16 m-wide and 16 m-high, convey the turbined water into the Kwanza River. The mass oscillation scheme designed for transient pressures consists of two surge chambers, with a required area of about 1 000 m2 each. The environmental flow power plant, at the toe of the dam, on the left bank, is equipped with a 52 MW Francis turbine, for a rated flow of 60 m3/s. This paper addresses the main aspects of the detailed design layout adopted for the tender of the Caculo Cabaça Hydropower Project, highlighting some major key components, in particular those regarding the dam.

ABSTRACT. Dams leak! But only some of the leaks require investigation and remediation. When they do, finding the pathway of the leak becomes an expensive and slow process, often characterized by drilling “trial and error” boreholes that further impair the integrity of the structure. A much better alternative is to collect specialized data with highly sensitive instruments along all relevant points, map the data using the latest groundwater geophysics technology or hydrogeophysics technology, create 3D models of the subsurface including the flow path of the leak in question, and finally use proprietary software filters and algorithms to predict ongoing effects of the water problem. In this paper three case studies are presented including the Bartley Dam, King George Dam, and the Samanalawewa dam. All of the dams had leaks that concerned the dam owners. The method was applied to determine the location of the seepage paths passing through the dam. Remediation was completed at the Bartley Dam and King George Dam confirming the results from the method. And there are plans for remediation at the Samanalawewa dam. The method saved the client significant amount of money because they had a focused remediation instead of drilling by trial and error. Knowing the dam has been repaired and there are no other leaks provides peace of mind to the dam owners.

ABSTRACT. The safety assessment of dams is a complex task that is made possible thanks to a constant monitoring of pertinent parameters. Once collected, the data is processed by statistical analysis models in order to describe the behaviour of the structure. The aim of those models is to detect early signs of abnormal behaviour so as to take corrective actions when required. Because of the uniqueness of each structure, the behavioural models need to adapt to each of these structures, thus flexibility is required. Simultaneously, generalisation capacities are sought, so a trade-off has to be found. This flexibility is even more important when the analysed phenomenon is characterised by non-linear features, as it is the case for the piezometric levels (PL) monitored at the rock-concrete interface of the arch dam that this study focuses on. In that case, the linear models that are classically used by engineers show insufficient performances. Consequently, interest naturally grows for the advanced learning algorithms known as machine learning techniques. In this work, the aim is to compare the predictive performances and generalization capacities of three different Data Mining algorithms that are likely to be used for monitoring purposes: Artificial Neural Networks (ANN), Support Vector Machines (SVM) and Multiple Regression (MR). The achieved results show that SVM and ANN stand out as the most efficient algorithms, when it comes to analysing non-linear monitored phenomenon. Through a global sensitivity analysis, the influence of the models’ attributes was measured, evidencing a high impact of Z (relative trough) in PL prediction.

ABSTRACT. Being able to describe the state of a dam regarding the safety requirements is an obligation that dam owners have to fulfil. A constant surveillance is thus established, based on the measurement of structural behavioural parameters. The provided data is used to feed descriptive statistical models which are classically linear, such as the historical HST (Hydrostatic-Season-Time) model. This assumed linearity is a significant shortcoming, which dramatically reduces the accuracy of the models when it comes to analysing the piezometry in the foundations of arch dams, and more particularly at the rock-concrete interface. Indeed, the contact between rock and concrete evolves during seasons between an open and closed state, under the influence of the thermal stresses, and of the cyclic hydrostatic load, but also with time during the years. Thus the effects of those three influencing loads on the piezometry are not merely additive. Consequently, analysing such a complex phenomenon with accuracy is only possible when considering complex interactions between the influencing quantities. This paper presents a model that describes the piezometry at the rock-concrete interface as being a fraction of the total upstream hydrostatic load. This fraction is directly linked to the deformations and the permeability variations of the rock mass in the foundations, which in turn evolve with the mechanical stresses that the whole structure (foundations plus dam) is submitted to. Since it has been empirically observed that the permeability variations and the piezometry are non-linearly correlated, this non-linearity is explicitly included into the model formulation. In this work, the resulting model is applied to analyse monitored piezometric levels recorded at the interface of a French arch dam. This approach greatly improves the analysis that could be made by HST, and it permits a thorough physical interpretation of the studied piezometry. Eventually, the temporal evolution of the state of aperture of the contact is assessed, which is a great improvement for dam monitoring.

ABSTRACT. The evaluation of the structural performance of Itaipu Dam involves, among other activities, the analysis of data from instruments installed at different points of the structures and their foundations. A widely used instrument is the piezometer, which allows monitoring of uplift pressures and pore water pressure occurring in the foundation of the structures and in the body of the earthfill and rockfill dams. The piezometers provide information regarding the pressures caused by water infiltration via discontinuities in the rock mass, as well as via the pores of the earthfill. The variable supplied by the piezometers is called piezometric head, which can be converted into pressure. Monitoring is carried out in several features over large areas, which in many cases include the whole foundation of Itaipu. The main features are the contacts between structure and foundation (concrete and rock or soil and earthfill) and discontinuity or porous zones (geological faults, basaltic breccias and fractured zones, in addition to strategic points in the embankment dams). In general, the analysis of these data is performed in a timely manner, using the time series obtained by the instruments, where current values are compared with historical highs and with theoretical values obtained via mathematical models that simulate critical load situations. However, spatial evaluation allows a greater understanding of the hydrogeological phenomena, since these do not occur locally, being instead results of features’ characteristics, of the drainage and waterproofing systems, and of treatments given to the foundation, as well as of the loads imposed by the presence of the reservoir and the rainfall patterns. Thus, this work aims to present the development of piezometric head and uplift pressure maps to modernize and improve the analysis of the performance of Itaipu's structures, based on mathematical interpolation and the use of Geographical Information Systems.

ABSTRACT. Dam owners gather monitoring measurements for surveillance and safety purposes, sometimes since the first impoundment. These measurements are often topographic surveys, displacements, piezometric measurements, or even flow measurements. These time series have a rich history, and therefore, today, it is logical to learn about the behaviour of structures from this rich database especially by using machine learning techniques. Among many of these powerful techniques, the use of artificial neural networks (ANN) has proven to be one of the most appropriate machine learning technique when applied to the analysis of data monitoring measurements. The paper briefly sums up the principle of artificial neural networks and their advantages when compared with the historical model HST (Hydrostatic-Season-Time) which is based on the multiple linear regression. Then, the home-made software NOVAE (Neural NetwOrks for Valuable Analysis and Expertise) is presented. NOVAE enables all engineers responsible for dam surveillance to use the technique of ANN when analysing monitoring measurements. The software is directly linked with the database which stores the monitoring data collected from the 320 dams monitored by EDF. Therefore NOVAE makes it easy to get interesting results without the need of specific skills in the field of machine learning techniques, and by simply using the default parameters which are preset. The advantages of using ANN are then illustrated for the analysis of piezometric levels at the rock-concrete interface of arch dams. In that case, the HST model has a low quality of prediction and is outperformed by ANN. As exhibited by NOVAE, ANN not only improve the numerical performance, but also the interpretation of the behaviour of the dam. Indeed, they allow to connect the loads (hydrostatic, thermal …) acting on the structure and their induced effects, even if their interactions are complex. Finally, the use of the ANN in an industrial context leads to a better assessment of the dams’ safety.

ABSTRACT. The Ribeiradio-Ermida multipurpose hydro electrical scheme, built between July 2010 and the end of 2015, is the first major project in the Vouga River basin, located in the centre of Portugal. Its main purposes are power generation, water supply and flood control. The main dam, Ribeiradio, is an 83 m high concrete gravity dam, with a controlled gated spillway over the dam structure. This project encompasses a second lower dam, Ermida, located 5 km downstream, to regulate Ribeiradio’s flows. Both schemes have been under operation since the first quarter of 2016. During the construction phase, some geological difficulties were found in the foundations of the two dams, related to very altered foundation zones and the presence of important faults, which motivated the adjustment of the final configuration of the excavations, as well as the geometry of the blocks of the dams. The first filling of the Ribeiradio dam reservoir was thoroughly accompanied and analyzed to adequately assess the dam and its foundation’s behaviour. For each reservoir filling stage, stipulated in the monitoring plan, the main loads and measurements of the representative parameters of the structural responses have been analyzed, envisaging the total reservoir filling under safe conditions. This paper presents the main aspects and results obtained during the first filling of Ribeiradio dam reservoir and during the subsequent period of exploitation until the end of 2017. In accordance with the Portuguese legislation, the results of the detailed inspections of the dam and its foundation, as well as the integrated analysis of all results obtained by the monitoring system, which will be presented in the paper, have shown a satisfactory behaviour of both the dam and its foundation.

ABSTRACT. Automatic Monitoring Systems of Dams Instrumentation is not commonplace in Brazil’s hydropower sector. However, these systems increase quality of data, frequency of acquisition, productivity and reliability, moreover provides agility in the decision making process, especially at the occurrence of exceptional events. In addition, the assessment of dam’s behavior becomes more consistent and reliable. Considering these aspects and the need for a more effective monitoring of Irapé Dam, the highest in Brazil, it was decided to partially automate the dam instrumentation. The article presents the results for the processes of “ Automation of geotechnical instrumentation at Irapé Dam” and “Integration to the system PIMS (Plant Information Management System)” whose purpose was to automate 49 vibrating wire piezometers, 7 V-notch weirs, 31 total pressure cells e 4 stand pipe piezometers. The automatic monitoring system comprises essentially dataloggers and multiplexers relays, radio frequency modules 900 MHz in a DigiMesh network and omnidirectional antennas, surge protectors, photovoltaic cells and batteries. Additionally to the software provided by the equipment’s manufacturer, it was still developed a System of Data Processing and Management, implemented at PIMS platform whose basic functions enables the analysis of pore water pressure, percolated flows and total and effective stresses. The data is updated every hour and it is shown in synoptic screens for the respective dam sections. Furthermore, comprises the instrumentation data management regarding threshold values based in deterministic and statistical approaches with alarms setting. The solution has been shown effective results to evaluate the performance of the dam.

ABSTRACT. This paper presents the updating of the behaviour analysis and interpretation of Cahora Bassa dam, a 166 m high double-curvature arch dam, located in the Zambezi river (Mozambique). The structural numerical model includes, in addition to the dam’s body with the mid-bottom spillway holes, already considered in the previous studies, the downstream structures of that spillway. The results computed with the updated structural model together with the data provided by the dam monitoring system, support the analysis and interpretation of the dam behaviour, since the first filling of the reservoir, occurred in 1974, up to the end of 2016. The structural model, based in 3D finite elements of the dam and its foundations, takes into account the concrete viscoelastic behaviour, the variation of the reservoir level and the expansions due to the moderate alkali-aggregate reactions (AAR) on the dam´s concrete. The monitoring and the numerical results display an excellent agreement, showing the suitability of the finite element model for modelling the dam’s behaviour. Additionally, the obtained results confirm the relevance and influence of creep and swelling effects in the dam structural response. Relatively to the stress fields, the computed results show that at the arch bearings the stresses assume already significant values. The displacements computed at the mid-bottom spillway structures are important data for verifying the operation of the gates.

ABSTRACT. This paper presents the relevant monitoring data and the main results of the analysis and interpretation of the structural behaviour of Bouçoais-Sonim dam, a medium-size gravity concrete dam of 42.5 m high, during the first filling of the reservoir, in March 2005, and the subsequent 10 years of operation. As usual, the dam safety control is performed by considering the data provided by the monitoring system, which is analysed and interpreted with the support of numerical models. These activities are particularly relevant during the first filling of the reservoir, which is a real load testing, and during the first years of operation, when the dam’s body and its foundation adapt to the local serviceability conditions. A three-dimensional finite element model of the dam and of the rock mass foundation, considering the concrete viscoelastic behaviour and the variation of the reservoir water level and temperatures, allows simulating numerically the thermal and structural dam behaviour. The dam’s concrete delayed behaviour was represented by the Bažant and Panula’s basic creep function, evaluated from ordinary concrete laboratory tests. The monitoring results, namely the displacements measured through plumb-lines, exhibit a good agreement with those obtained by the structural analysis, showing that the observed response is coherent with the evolution of the main actions.

ABSTRACT. In the state of Ceará, the Water Resources Management Company (COGERH) is the public agency responsible for the dams management system. Under Law No. 12334/2010, it is an entrepreneur that has the provision of the necessary resources to guarantee the safety of the dams and carry out safety inspections among its duties. Since 1995, COGERH already considered dam safety aspects in its activities, however nowadays it is duty of the Water Infrastructure and Security Management (GESIN) with the support of a regional organization management system that covers the entire state area. A Reservoir Gard and Inspection Agent (AGIR) trained by GESIN’s technicians to perform basic maintenance actions and support safety inspections monitor the Company’s dams on a daily basis. In order to conduct regular safety inspections of the dams, the Company has prepared a checklist, which considers the main anomalies observed in the dams and their associated structures. This checklist is applied by a regional management technician, who is qualified to fill it out by GESIN, and from the results obtained in these inspections, it is possible to classify the dams according to their level of danger as the intervention priority. In this context, an analysis of the results obtained with this safety methodology between 2010 and 2016 was carried out to verify its efficiency within the State's dam safety system. To do so, based on the database obtained from the period in question, a descriptive statistical analysis was performed in order to diagnose the evolution of the application of the methodology. With the obtained results, it was possible to observe the evolution of the level of danger of the state dams, besides the main structures that present a greater frequency of anomalies. However, it was also observed that the methodology presents some inconsistencies, mainly due to the fact that the results of the safety inspections vary greatly according to the technician who performed it. Therefore, it is concluded that the methodology developed and applied by COGERH in the State of Ceará is a reference in the country in the field of dam safety, but needs improvements so that it can present data that reflects the state of conservation of the monitored dams more realistically.

ABSTRACT. Recent regulatory changes related to dam safety in Brazil have altered the way entrepreneurs deal with their structures. In addition to the creation of the National Dam Safety Policy, in 2010, the collapse of the tailings dam in Mariana/MG also changed the role of government surveillance and inspection. The Gegraf dam, a small dam in the south of Minas Gerais, clearly exposes the effects and impacts of those changes. The water storage dam is only 9.0 meters height, has a storage volume of 0.092 hm³ and does not have relevant anthropic occupation in the downstream valley. If it was not for the industrial purpose of its use, the dam would not meet the minimum required parameters to be monitored and inspected. A state regulation determined that the structure should be inspected annually by a dam safety specialist and the all the maintenance recommendations had to be performed. Due to many shifts in the company’s management and ownership, a series of relatively simple anomalies worsened overtime, raising the cost of maintenance to a point that the best strategy was decommissioning the structure and looking for another water source. This measure reduced the operating costs of the company, as well as the risks to the business. This is an example of how regulation imposed on conscious entrepreneurs can contribute to the safety of an entire downstream valley.

ABSTRACT. With the issue of Law No. 12.334/2010, which created the National Dam Safety Policy, the National Water Agency (ANA for its acronym in Portuguese) became the enforcement body of the safety of multiple-uses dams in federal rivers. After consolidating the dams record under its jurisdiction, ANA came to understand the great challenge it was to classify these structures, mainly as to the Hazard Potential (DPA for its acronym in Portuguese), due to the precariousness of the relief data and other data from these dams. To establish the classification procedures, ANA was supported by the World Bank, with the participation of the National Laboratory of Civil Engineering (LNEC for its acronym in Portuguese) from Portugal. One of the products developed was a simplified method for determining the flood area due to dam break, based only on data such as height, volume and location and using the Shuttle Radar Topography Mission (SRTM) as the digital elevation model. The resultant polygon is suitable only for classification purposes and does not replace the dam break study to be carried out by the responsible for the dam. ANA adapted the methodology developed, both for the generation of the simplified flood polygon and for the criteria described in the classification matrix of the National Water Resources Council (CNRH for its acronym in Portuguese). Following the classification of 136 dams by DPA, the conclusions are that the method for generating the simplified flood polygon is a cheap and easy-to-use tool, recommended mainly for the classification of dams, or even for an initial estimation of flooded area, ideal for enforcement bodies with little information and lack of qualified personnel to perform more complex simulations. The greater challenge observed relates to very small dams, where the resulting simplified polygon is too conservative, often leading to the suspicion that the obtained DPA is overestimated.

ABSTRACT. In 2010, the National Dam Safety Policy, regulated by Law nº 12334, establishes as one of its instruments the classification of dams by category of risk and hazard potential (DPA). The classification by category of hazard potential refers to the potential human and economic losses, as well as social and environmental impacts caused by the rupture of dams. In this context, 74 dams located in the state of Ceará, with storage capacities varying from 0.83 to 380 hm³, were classified by DPA following the criteria established by the National Council of Water Resources (Resolution nº 143/2012). In order to classify dams, it is necessary to generate flood areas. Thereby, the simplified methodology proposed by the National Water Agency – which requires as input data the reservoir volume, the height of the dam and the crest of spillway level – was adopted in this paper. It is also required topographic data for which a digital elevation model was used. The results obtained for the classified sample were very relevant to the state of Ceará, in which all the classified dams presented a high level of hazard potential. This is because the human settlements in the state of Ceará are culturally in areas near to water bodies, which leads to a great occupation of the regions downstream from the dams. Therefore, it is concluded that this classification is extremely important to the development of a dam safety policy in the state.

ABSTRACT. The long-term behavior of concrete is an important topic where critical infrastructure projects are concerned. Deterioration of concrete structures subjected to aggressive water is often characterized by the leaching process that occurs gradually in structures in long-term contact with water. Leaching or lime-leaching refers to CaO (in reality Ca2+ and OH–) being removed from the concrete by dissolution in water. Leaching enlarges the pore system of the concrete temporarily increasing the permeability, although dissolved ions may later precipitate inside the pore system, reducing the permeability of the parts involved. Some variables are involved to a greater or lesser degree in such an event, such as hydrostatic pressure or environmental conditions. This study aims to advance research related to the leaching process in the foundation concrete of the Itaipu hydroelectric powerhouse. Previous analysis carried out up to 1993 indicated that there were no risks to the stability of this structure, which could negatively impact the operation of the electromechanical equipment, this being the reason why these analyzes have been partially discontinued since then. Although the instrumentation demonstrates satisfactory behavior of this section, there have been no specific studies regarding the recent characteristics of this section’s concrete. Among drains that exist in this region of the foundation, three of them concentrate the largest flows, currently about 2 l/s, whose chemical analyzes indicate that the concrete leaching still occurs, although the dissolved compound contents are much smaller than those at the beginning of the process. Concrete samples will be extracted to carry out laboratory tests, including compressive strength, to complement chemical tests and establish correlation between them, analyzing the long-term effects of leaching in this section.

ABSTRACT. The project of Logs Overflowing System, what is part of civil structures of Santo Antonio Hydroelectric Plant located in Porto Velho, state of Rondonia in Brazil, was developed due to the peculiarities of Madeira River. This river has a significant content of logs, trash and other kinds of floating masses throughout its course mainly in flooding times. A number of 7500 units per day of these materials can be registered during floods. The transposition project of these floating materials was initially concepted considering metalic covering (ogive shielding) and sill protection with rails, in order to guarentee the integrity of hydraulic surface, regarding to abrasion and to other types of impacts caused by large logs, mainly the ones with diameters higher than 0,50 meters. Due to the deadlines, concrete with special performance would be considered for construction, besides for being the best technical and economic choice. So, steel fiber-reinforced concrete (SFRC) was chosen, made with a specific technique and placing for large structures. This application was pioneer in a large structure, once this type of concrete was considered only in experimental areas with different types of fiber. The fiber content in concrete was 80 kg/m³, obtained by dosage studies developed by Furnas staff, in charge of quality control. The studies took into account the needed characteristics for casting and production, besides the requirements of tensile strength and surface abrasion due to high index of residue and to support the log impacts on the structures during spilling. Due to the required characteristics for the structure and the pumping, with steel fiber replacing shielding and rails, this methodology can be considered unprecedented and pioneer, mainly as integrated project design, in hydraulic constructions. Thus, this paper presents the performance evaluation after the first years of operation, with topics about the concrete durability.

ABSTRACT. After the severe accident occurred in Mariana – MG State, in 2015, with the rupture of the Fundão Dam, several safeguard measures, mainly in terms of policy, have been taken as a concern for a guarantee of Brazilian dams. The objective of these initiatives is to increase the rigor of controls and monitoring, including a regulation of the Dams Security Plan by the National Electric Energy Agency - ANEEL, pursuant to resolution 696/2015.

In the present work, Furnas Centrais Elétricas shows results of a methodology that is being studied by our teamwork since 2012, to investigate the leaching of concrete, through the loss of ionic mass.

In a simplified way, the methodology consists of calculating the loss of mass of the dam concrete over time, by comparing the chemical results of the water upstream of the reservoir and the ones obtained through the drains. It was possible to calculate the difference in the amount of ions and other compounds (Ca, Al, Na, Fe, CaCO3) contained in the water of the drains and the water components of the reservoir. Studies have shown that this methodology can be another tool used to ensure the safety of dams.

ABSTRACT. Expansive reactions are a common pathology in concrete dams. The most usual alkali-aggregate reaction (AAR) and the less frequent internal sulfate attack (ISA) have been extensively studied. The causes, the chemical reactions and the resulting products are well-known. To provide further insight, this paper presents the lessons learned along the 30-year experience of a group dedicated to the diagnosis and study of concrete dams with expansions, illustrated with two real cases.

The first case corresponds to a gravity dam built in 1971 and monitored for more than 35 years that exhibits non-recoverable displacements (up to 220 mm) and cracking. The studies of the late 1980s and early 1990s suggested an ISA as the cause of the behavior observed at the time. However, the evolution of the displacements and the development of new cracks detected since 1993 could not be justified with the original diagnosis. A thorough and comprehensive study conducted in 2014 allowed identifying two reactions within the concrete: an ISA and an AAR. The confluence of two expansive reactions is uncommon and it is precisely this rarity that makes this dam a valuable case of study.

The second case is an arch-gravity dam built in 1969 that presents cracks and non-recoverable displacements. The “symptoms” detected suggested an ISA; however, the effects of this reaction were localized in areas of the dam, contrarily to what the authors had observed in other dams. The study of historical records revealed that the aggregates used to produce the concrete were obtained from different locations in the same quarry. The first location was abandoned shortly after the construction started and most of the concrete of the dam was produces with aggregates from the second location. The study conducted revealed that the aggregates contained iron sulfides, particularly those from the first location. Interestingly, the blocks containing aggregates from the first locations are those presenting higher horizontal and vertical displacement as well as mapped cracking.

ABSTRACT. The state of Espírito Santo has one of the largest granite reserves in Brazil. The production process in the beneficiation of granite is generated wastes that, in part, are used in the manufacture of bricks and agricultural defenses or are only discarded. This residue, most of the time, ends up being sent into nature as a trash, without the due environmental care. Such use or discard can be easily detected in the city of Cachoeiro de Itapemirim, located in the south of Espirito Santo. In this case study, the use of granite will be studied in a sustainable way, through the use in the production of concrete (CAA). The chemical properties of the active silica particles present in the crushed granite are able to react with the alkalis of the Portland cement. In this study, the crushed granite was replaced by tiny or large aggregates in a rate of 100%. We analyzed the effects of replacing in the properties of the self - compacting concrete (CAA) for the consistency in the fresh state, in the mechanical resistance to compression and durability. As for the durability, immersion of the test specimens was done to obtain capillary parameters. Tests of granulometry were performed according to the current NBR. The concrete produced was studied from the beginning of the handle in 3, 7, 21, 28 and 96 days, following the NBRs. This study intends to analyze the feasibility of the use of crushed self-solid - compacting concrete (CAA), studying its influence on mechanical resistance to compression, in the reduction of indices of voids and porosity. This study also aims to contribute to the reduction of the environmental impact caused by the extraction of this residue, the volume of residuals, would give for 60 years without extraction of the tiny aggregate, since 32% of this mineral extraction is absorbed by the building industry.