Assessment of concrete–rock contact shear behaviour based on in situ shear tests

Defining shear strengths of concrete–rock contacts is extremely important for designing concrete structures such as arch and gravity concrete dams that are constructed on rock. Assessment of 34 large-scale in situ direct shear tests conducted on concrete–rock contacts of various roughnesses is presented in this paper. Evaluation of the peak strength results at moderate-to-low stress ranges, indicates that a non-linear trend with maximum at moderate roughness (joint roughness coefficient, JRC = 11–12) can reasonably represent relationships between peak and apparent shear strengths, shear stiffness and shear displacement relationships with respect to JRC. Apparent residual strength parameters appear to show a more linear Mohr–Coulomb to slightly non-linear trend with JRC and applied normal stress.