Assessment of the Influence of the Degree of Weathering on the Shear Strength of Smooth and Bonded Concrete-Rock (Gneiss) Interfaces

The concrete-rock interface is considered one of the most fragile regions of a concrete dam. In general, concrete dam projects consider the premise of being supported on good quality rock. However, in tropical countries, there is a greater influence of weathering on rock and, therefore, situations in which the characteristics of the rock are worse than expected are commonly identified. As a result, this article aims to present the results of an evaluation of the behavior of interfaces, connected and supported, of concrete-gneiss, considering the degree of weathering of the rock and the adhesion of the concrete. The influence of the degree of weathering on the shear strength of the interface was based on direct shear test results performed on samples with different degrees of weathering. The characterization of the degree of weathering was made on visual inspection and based on laboratory test results from physical and petrographic characterization. In general, the results showed good correlations between the physical properties of the rock and the shear strength of the interfaces with different degrees of weathering, with a more significant reduction in the strength parameters for samples with smooth surface.