The uncertainties surrounding the composition and behaviour of most old embankment dams are so great that a purely analytical approach to dam safety evaluation is unlikely to be adequate and an observational approach is needed. The monitoring of the deformations of embankment dams has an important role in assessing longterm behaviour and in evaluating safety. This paper describes field studies at five old embankment dams all constructed in the Pennines, Yorkshire. It has been confirmed that where there is a central core, significant crest settlement can be expected on reservoir drawdown, but this is not the case where there is an upstream watertight element. The field studies should aid the interpretation of observations associated with reservoir drawdown and assist both in identifying anomalous behaviour associated with deleterious processes and in preventing behaviour associated with steady-state loading and reservoir fluctuations giving unnecessary cause for concern. On est tellement incertain de la composition et du comportement de la plupart des vieux barrages remblayés qu'une évaluation purement analytique de la sûreté des barrages laisse probablement à désirer et qu'une démarche basée sur l'observation s'impose. La surveillance des déformations des barrages remblayés joue un rôle important dans ľvaluation du comportement à long terme et dans 1'évaluation de la sûreté. Ľexposé décrit les études sur le terrain dont ont fait l'objet cinq vieux barrages remblayés des Pennines. Elles ont confirmé qu'il faut s'attendre à un tassement substandel du couronnement de barrages à noyau central lors de 1'évacuation du réservoir, à moins qu'il n'y ait un masque amont. Les études sur le terrain devraient alder à interpréter les observations faites lors de ľévacuation des réservoirs et à définir les comportements anormaux qu'on associe à des processus préjudiciables, ainsi qu'à prévenir les comportements associés à un niveau Wean constant ou & agrave; des fluctuations du niveau Wean, qui suscitent des inquiétudes inutiles.
High alumina cement (HAC) concrete was used extensively in the UK from the 1950s to the early 1970s in the manufacture of precast, prestressed concrete beams. Long-term durability problems have now begun to affect these elements, the most important of which is reinforcement corrosion due to carbonation of the cover concrete. A ten-year programme of research, funded by the DETR, was initiated at the Building Research Establishment in 1993 to provide data on the rates and mechanisms which control carbonation and reinforcement corrosion in HAC concrete. This paper reviews data obtained over 5 years. Carbonation depths and rates for the HAC concretes studied were found to be influenced by water/cement ratio, curing and exposure conditions, in a similar manner to Portland cement (PC) concretes. The carbonation rates appeared to be the same as those for PC concretes with 28-day compressive strength properties similar to the fully converted (minimum) strength of the HAC concrete. The majority of the steel in specimens exposed in natural conditions was still in uncarbonated concrete after five years' exposure. The risk of reinforcement corrosion in these specimens was therefore low. However, electrochemical measurements taken on fully carbonated specimens illustrate the strong relationship between the availability of moisture, concrete resistance and the rate of corrosion.
Access to this document was granted through an Emerald subscription provided by emerald-srm:233725 [] For AuthorsIf you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractThis paper reviews the techniques available for assessing the material characteristics and long-term performance of high alumina cement concrete construction. The use of some of these techniques is illustrated in a case study on typical pre-cast concrete beams. Electronic accessThe research register for this journal is available at
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