BARRAGENS DE ENROCAMENTO COM FACE DE CONCRETO PDFJune 21, 2020
As barragens de enrocamento com face de concreto (BEFC) têm sido construídas com freqüência crescente em todo mundo. Apesar disso, os critérios de. Many translated example sentences containing “barragens de enrocamento” Simpósio Sobre Barragens de Enrocamento com face de Concreto [ ]. 15 out. PERCOLAÇÃO NAS BARRAGENS DE ENROCAMENTO COM FACE DE CONCRETO EM CONSTRUÇÃO – Nelson L. de S. Pinto.
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Skip to main content. Log In Sign Up. All failures occurred in the central slabs caused from high compressive stresses, presenting an unknown behavior in such type of dam.
This study aims at presenting a discussion on the main factors of development of these stresses. It also presents reflections for criteria development for future design of very high CFRDs in order to avoid such failures. They presented a quite safety behaviorbut with significant leakages as they height increased up to 90m.
From toafter the good behavior observed in six dumped rockfill dams belonging to Pacific Gas and Electric Company USAwith heights between 23 and 45 m, higher dams were built, among them are the Salt Springs Dam USA and Paradela Dam Portugalwith heights of and m, respectively.
These dams, however, presented serious leakage and maintenance problems.
II SIMPÓSIO SOBRE BARRAGENS DE ENROCAMENTO
Such failures motivated the abandonment of this type of solution for dams until when, with the development of heavy vibrating rollers for compaction of rockfill in layers, high rockfill dams with clay core started to be built.
The success of these dams, with heights bargagens up to m Harragens Dam, in Mexicorestarted the construction of concrete face rockfill dams, attractive barrxgens their lower cost and shorter time of construction when local rain fall conditions are restrictive for soil compaction. Except for the Salvajina dam, the others were built in narrow conccreto.
However, some of these dams presented infiltration problems. Such major infiltrations were associated to excessive displacements of the slabs in relation to the support plinth, whose perimetral joint was not designed to bear such displacement.
This problem was solved in further dams by changing the zoning of the fill material in the region of interest and new design of the perimetral joint, which had more than one sealing element and, as an additional defense line, when viable, a clay fill on the perimetral joint. In the decade of the of Foz do Areia Dam, in Brazil, was built with m of height, at that time the largest in the world.
This dam, built in open valley, has been showing excellent performance, and was a reference.
Comm Cooke died in He received many awards for his brilliant professional performance, such as the Distinguished Engineering Alumnus Award, from the University of Berkeley — California, and the Cace Lecturer offrom the American Society of Civil Engineers.
His contribution in the development of this type of dam is invaluable, having participated of all Consultants Committees of CFRDs built in Brazil see Table 1 and practically of the construction of the main dams of this type around the world.
The basic principle stated by Cooke – Ref. This would be an acceptable approach for CFRDs have intrinsic stability in function of the following features: Cracks may occur in the concrete face; they would be tolerable since the embankment resists to the flow and the cracks can be easily sealed by placing fine material sandy silt.
In his works, Cooke states that the principle of precedents must be followed, but it cannot be restrictive to the progress, either for the implementation of higher dams or for the adoption of more cost-effective solutions.
Thus, progressive modifications were introduced in the CFRD design, among them: These modifications were successfully introduced in dams built in Brazil and in the world; however, all of them with height below m the height of Foz do Areia dam.
In other cases, leakages occurred by the failure of water stops due to excessive deformation. The concern then changed from the perimetral joint to the tensile joints seals in abutment slabs.
Flávio Alberto Crispel
Numerical model analyses were done to predict probable displacements of the concrete face, which were then imposed to the slabs to obtain the respective stresses. Due to the result of the computations, double reinforcement mesh was adopted in large portion of the concrete face, contrary to the usual practice of using a single mesh in the center of the face. It is worth repeating the technical contribution of Mr. barrqgens
Barry Cooke enrocaamento invaluable. However, it seems that his confidence in the stability of this type of dam regarding its resistance to normal operation loads and to the action of eventual water seepage led to adoption of some practical design criteria not totally applicable in very high dams built in narrow valleys, where stress levels extrapolated the already experienced values.
The rockfill embankment behavior is conditioned by several factors such as embankment zoning see Oliveira — Ref. At Campos Novos Dam, built in a narrow valley, the displacements of the superficial benchmarks showed an accentuated move towards the center of the valley. This enrocmento doesn’t consider the joints between the slabs of the concrete enrocaemnto. It must be pointed out that this feature is critical on abutments.
Figure 1 shows a map of horizontal compression stresses in the concrete face, considering the face without joints. Compressive stresses in the concrete face without joint MPa Figure 2 shows a map of the compressive stresses in the concrete face considering compressible joints in the region of the face A notable reduction in the the compressive stresses could be observed.
Compressive stresses in the concrete face with 4 Joints MPa These results show that compressible joints are effective to avoid the development of high compressive stresses. For a more favorable behavior in relation to these efforts, the concrete face should be divided into panels that can reduce or eliminate some of the soliciting efforts above mentioned.
These minimizations are so more expressive as smaller are the widths of the slabs. Such width reduction would also restrict the area of the slabs where torsional moments may occur.
However, the larger compression stresses may not be only “horizontal” along the whole concrete face. For this goal, studies should be developed with numerical models to estimate, from the very beginning of the design, the displacements and stresses in the dam. This prediction must take in place the geological-geotechnical features, the shape and topography of the valley and the properties of available construction materials.
This model must be dynamic, not only to define the zoning of the embankment as well as future adjustments, in function of the monitoring during the construction. Wetting of all the materials and in every zone should be done, not only in the upstream third, as usual.
Also the thickness of the compaction layers should be adjusted, in function of the quality, gradation and shape of materials and of the type of compacting roller used. Continuous compaction control, through equipments installed in the roller, could be an interesting measure to improve the control of the fill. The instrumentation of the embankment and of the concrete face should be intensified to reflect dam performance, mainly of its singularities.
The results should ccom continuous analysis to allow the necessary actions in the design and in the constructive methods. Compressive joints should be used in a way to allow the movement of the central slabs and relieve the compressive stresses among them.
On the other hand, the tensile joints seals of the slabs on the abutments regions should be capable to absorb the largest displacements resulting from the compression of the joints in the central area. These suggestions should be analyzed for each case.
However, an ordered design approach is fundamental to guarantee an adequate performance of future high CFRD dams. Remember me on this computer. Enter the email address you signed enrocameno with and we’ll email you a reset link.
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