engleski

A case history of consolidation of the Botonega Dam

During construction of the Botonega dam, instruments were installed to measure settlements of the dam foundation and embankment. Due to inadequate site preparation and improper instrument installation, the results of measurements obtained do not give a real picture of the behaviour of both the dam and the foundation. So far reliable data have been obtained only by geodetic measurements at 41 measuring points spread over 12 profiles. Regrettably, a zero measurement was made, i.e. the first geodetic measurements took place, only five years after the start or two years following the completion of the dam construction. Thus no surveys were carried out of unloaded foundation or of the behaviour of the dam and foundation in the early stages of construction when most significant settlements occurred. In order to reconstruct previous consolidation processes and to predict the future ones, a numerical model was worked out. The sizes of the model and properties of materials used were determined based on the results of investigations, design and construction documents, as well as the results of annual monitoring, which included detailed data on the behaviour of the dam. Two constitutional models were used: the Mohr-Coulomb elastic-perfectly plastic model (MC model) and the hardening soil model (HS model). The latter model takes into account stress-strain nonlinearity and different loading/unloading material behaviour. Settlement values obtained by computing and geodetic measurements correspond well. As for stress-strain characteristics of materials, at the time when the dam was being designed, researches were not focused on determining elastoplastic properties of the materials because then no appropriate software was available. For this reason, some material parameters required for the MC model, and especially those for the HS model had to be derived from available data and from the literature.

dam; settlement; consolidation; case history

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