Shear Strength of Concrete Lift Joints from Extensive Lab Testing Compared to Theoretical Results

Abstract

During recent assessment of the Tennessee Valley Authority (TVA) dams, TVA has developed a systematic approach for determining shear strength parameters for use in the stability analysis. This systematic approach involved extensive field investigations which included drilling and sampling of concrete and rock cores. The core samples were then  used in a laboratory strength testing program. As part of this work, concrete core strength testing involved testing for compressive strength, tensile strength (direct and splitting), and shear strength (lift joints and parent concrete). This paper will present the results of the strength testing (graphically) and provide discussion on the results. The results from several TVA dams will be presented. A comparison of direct tension and splitting tensile strength is provided and discussed. In addition the measured shear strength of lift joints and parent concrete is compared to results from previously published theoretical equations (Curtis, 2011). Finally, recommendations will be made for estimating shear strength of concrete (including lift joints) which can be used in the assessment of concrete gravity and arch dams.