Modelação do comportamento térmico do betão em massa : aplicação a uma barragem de BCC

A presente dissertação tem como objectivo efectuar o estudo do comportamento térmico de estruturas com betão em massa através do Método de Schmidt e compará-lo com outros métodos. A análise do comportamento do betão reveste-se de extrema importância em diversos domínios, de entre os quais se pode referir o que visa evitar a fissuração de origem térmica decorrente do calor de hidratação. Pelo motivo enunciado torna-se necessária dispor de metodologias de análise que requerem a mobilização de meios de cálculo. Existem diferentes métodos para o cálculo das temperaturas: uns mais simples, outros mais complexos, uns mais rápidos, outros mais demorados, uns mais onerosos e outros mais económicos. O conhecimento dos vários métodos permite adequá-los à especificidade de cada obra. Para realizar os vários procedimentos pode recorrer-se a programas informáticos de cálculo, como por o Excel ou utilizar Software Específico. Nesta dissertação apresenta-se uma metodologia de cálculo baseada no Método de Schmidt e faz-se a comparação com o Método de Solução Analítica. Utiliza-se também este Método no cálculo das temperaturas das várias camadas de uma barragem. O Método de Schmidt é ainda aplicado a um caso real de uma barragem da Tailândia construída em Betão Compactado com Cilindros e os resultados obtidos são comparados com outros Métodos de Análise Numérica de Barragens.

El proyecto hidroeléctrico del Arenal y el impacto en su entorno económico y social 1950-1994

Resumen Analiza el impacto que tuvo la construcción del proyecto hidroeléctrico del Arenal y con base en historia oral recuperar la opinión de los campesinos cuyas tierras fueron inundadas por el embalse. Abstract The author analyzes the impact of the construction of the Arenal hydroelectric project, and uses oral history to uncover the opinion of those peasants whose lands were flooded by the dam´s construction.

Earth and rock-fill dams, general design and construction considerations.

"This manual supersedes EM 1110-2-2300, 1 April 1959" issued under title: Earth embankments.

Indian storage reservoirs with earthen dams: being a practical treatise on their design and construction.

Blank pages for notes included in paging.

Tables for facilitating the calculation of earthwork in the construction of railways, roads, canals, dams, etc.,

Mode of access: Internet.

Rules for construction and maintenance of dams /

Includes: Recommended guidelines for safety inspection of dams / Dept. of the Army. Office of the Chief of Engineers ER 1110-2-106.

Analysis of stability of earthen dams in kachchh region, Gujarat, India

The Kachchh region of Gujarat, India bore the brunt of a disastrous earthquake of magnitude M-w=7.6 that occurred on January 26, 2001. The major cause of failure of various structures including earthen dams was noted to be the presence of liquefiable alluvium in the foundation soil. Results of back-analysis of failures of Chang, Tappar, Kaswati and Rudramata earth dams using pseudo-static limit equilibrium approach presented in this paper confirm that the presence of liquefiable layer contributed to lesser factors of safety leading to a base type of failure that was also observed in the field. Following the earthquake, earth dams have been rehabilitated by the concerned authority and it is imperative that the reconstructed sections of earth dams be reanalyzed. It is also increasingly realized that risk assessment of dams in view of the large-scale investment made and probabilistic analysis is necessary. In this study, it is demonstrated that the probabilistic approach when used in conjunction with deterministic approach helps in providing a rational solution for quantification of safety of the dam and in the estimation of risk associated with the dam construction. (C) 2007 Elsevier B.V. All rights reserved.

WATER-QUALITY CHANGES AND EFFECTS ON FISH POPULATIONS IN THE HANJIANG RIVER, CHINA, FOLLOWING HYDROELECTRIC DAM CONSTRUCTION

Since its completion in 1973 the Danjiangkou Dam has markedly changed downstream flows, water levels, temperatures, sediment loads and other water quality characteristics in downstream reaches of the Hanjiang River. There have been changes in the growth, spawning behaviour and overwintering condition of local fish populations, in the composition and abundance of food organisms and in the composition of the commercial fish catch. Despite the changed environment and the absence of a fish pass, fish populations are still able to grow and spawn under the new regime. Where conditions are like those of the Hanjiang River, dams may not necessarily have calamitous consequences for fishery production.

Population structure of the migratory fish Prochilodus lineatus (Characiformes) from rio Grande basin (Brazil), an area fragmented by dams

1. Prochilodus lineatus (Prochilodontidae, Characiformes) is a migratory species of great economic importance both in fisheries and aquaculture that is found throughout the Jacui, Paraiba do Sul, Parana, Paraguay and Uruguay river basins in South America. Earlier population studies of P. lineatus in the rio Grande basin (Parana basin) indicated the existence of a single population; however, the range of this species has been fragmented by the construction of several dams. Such dams modified the environmental conditions and could have constrained the reproductive migration of P. lineatus, possibly leading to changes in the population genetic structure. 2. In order to evaluate how genetic diversity is allocated in the rio Grande basin, 141 specimens of P. lineatus from eight collection sites were analysed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with 15 restriction enzymes. 3. Forty-six haplotypes were detected, and 70% of them are restricted. The mean genetic variability indexes (h = 0.7721 and pi = 1.6%) were similar to those found in natural populations with a large effective size. Fst and Exact Test values indicated a lack of structuring among the samples, and the model of isolation by distance was tested and rejected. 4. The haplotype network indicated that this population of P. lineatus has been maintained as a single variable stock with some differences in the genetic composition (haplotypes) between samples. Indications of population expansion were detected, and this finding was supported by neutrality tests and mismatch distribution analyses. 5. The present study focused on regions between dams to serve as a parameter for further evaluations of genetic variability and the putative impact of dams and repopulation programmes in natural populations of P. lineatus. Copyright (C) 2011 John Wiley & Sons, Ltd.

Monitoring Surface Displacement of the Colby Green Retaining Pond Dams

The Colby Green is a campus expansion project which began in October of 2003. The construction would result in three new buildings, additional parking, and an elliptical 75,000-squarefoot green southeast of Mayflower Hill Drive. There were also plans for the construction of three run-off management and sediment ponds below the green, to manage flooding of the green. Three drains in the green transport water to the three retaining ponds which slowly disperse water into the surrounding environment. The ponds were created by constructing earthen dams around the drain outlets. The dams are composed of soil, cobbles, and boulders procured from the surrounding excavation site. Unfortunately, earthen dams are susceptible to many types of erosion which result in their failure. In this case the potential for clay and silt from the underlying Presumpscot Formation to mix with the soil in the earthen dams raised concerns with regards to frost action. In order to monitor the surface displacement of the dams I drove 92 poles into the ground in 8 straight lines across the faces of the dams in the fall of 2005. I returned to the sites during and after the spring thaw of 2006, to check for any signs of movement resulting from frost-heave, surface creep, or any other form of mass wasting. Fortunately, there was no recordable sign of movement in the stakes across any of the retaining ponds. The dams appear to be functioning as designed.

Fish Migration, Dams, and Loss of Ecosystem Services in the Mekong Basin

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin's fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur.

Impact of dams, dam removal and dam-related river engineering structures on sediment connectivity and channel morphology of the Fugnitz and the Kaja Rivers

In terms of changing flow and sediment regimes of rivers, dams are often regarded as the most dominant form of human impact on fluvial systems. Dams can decrease the flux of water and sediments leading to channel changes such as upstream aggradation and downstream degradation. The opposite effects occur when dams are removed. Channel degradation often requires further intervention in terms of river bed and bank protection works. The situation evolves more complex in river systems that are impacted by a series of dams due to feedback processes between the different system compartments. A number of studies have recently investigated geomorphic systems using connectivity approaches to improve the understanding of geomorphic system response to change. This paper presents a case study investigating the impact of dam construction, dam removal and dam-related river bed and bank protection measures on the sediment connectivity and channel morphology of the Fugnitz and the Kaja Rivers using a combination of DEM analyses, field surveys and landscape evolution modelling. For both river systems the results revealed low sediment connectivity accompanied by a fine river bed sediment facies in river sections upstream of active dams and of removed dams with protection measures. Contrarily, high sediment connectivity which was accompanied by a coarse river bed sediment facies was observed in river sections either located downstream of active dams or of removed dams with upstream protection. In terms of channel changes, significant channel degradation was examined at locations downstream of active dams and of removed dams. Channel bed and bank protection measures prevent erosion and channel slope recovery after dam removal. Landscape evolution modeling revealed a complex geomorphic response to dam construction and dam removal as sediment output rates and therefore geomorphic processes have been shown to act in a non-linear manner. These insights are deemed to have major implications for river management and conservation, as quality and state of riverine habitats are determined by channel morphology and river bed sediment composition.

Simulation of Temperatures and Stresses during Construction of a RCC Dam

Se describen las variaciones de temperaturas y de tensiones durante la construcción de presas de hormigón compactado. The curing of concrete is an exothermic process. The heat of hydration generated induces temperature increases in the concrete, which will disappear in the long term by heat conduction in the concrete mass and thermal exchanges with the environment. The problem is of particularly interest for large concrete masses, as is the case of dams, because the time involved in the heat diffusion process grows with the square of the dimensions and a hotter dam interior implies the possibility of cracking the exposed surfaces of the dam. The Cuira dam, currently being built in Venezuela using roller compacted concrete, is a 134 m high, arch-gravity dam. In support of the design, different strategies were analysed, including various combinations of cooling of the water and the aggregate in order to achieve acceptable results. The calculations were conducted with Abaqus, taking into account all the necessary mechanical and thermal characteristics, as well as the relevant non-linearities. The analyses led to the conclusion that no cooling was required, even taking into account the stress state imposed by an early and rapid filling of the reservoir.

Design and construction of the Barriga Dam spillway through an improved wedge-shaped block technology

The Barriga Dam (Burgos, Spain) is a unique case study because its trapezoid spillway is located on the dam body and is composed of wedge-shaped concrete blocks (WSB) that include certain relevant improvements. This note summarizes the main features of the studies, the key aspects of the final design of the WSB and their placement on the dam, and important details of the spillway design. The design team concluded the study by showing the suitability of this enhanced technology for application to small dams and ponds in the short term, even with unit flows above 5 m2/s.