Boreholes in site investigation for dams on rock masses - How much is done in Portugal

Abstract

During site investigations (S.I.) for dams or other major projects, there is a fundamental question that always arises and which deals with the extension of the borehole programmes, this is, the amount of those type of works that should be done. This is a very important question which answer depends upon both the amount and the type of geotechnical information needed for the design and the amount of money allocated for the S.I. by the owner. People involved with S. I. frequently ask if the extension of studies by boreholes are over or under what that can be considered as normal or reasonable. This paper presents the portuguese experience on the amount of work by boreholes in S. I. for dams (arch and earth dams) on rock masses, based upon data collected from about 30 of the most recent dam projects. Trends on the amount of work in relation with some parameters that reflect the importance of the projects are also presented.