Surface stress relief zone in a rock mass ldentified through water and grouting tests

Abstract

ln the Amazon region, at a dam site under investigation, the phenomenon of surface relaxation of the rock mass, due to natural causes, was identified and characterized in three different ways:  water tests under pressure along bore holes, analysis of «backflow» observed in a certain number of holes and, finally, grouting tests.

The analysis of each type of test individually and in conjunction permitted the preliminary identification of horizontal zones of the rock mass, each one with particular hydrogeotechnical and deformability characteristics.

This discretization represented an important contribution to the discussion and project of the foundation treatment of the dam, permitting a substantial reduction in the extension and magnitude of the work, as compared to other projects of the same size.