Volume 25, Issue 4 (December 2002)
Laboratory Testing of Concrete-rock Joints in Constant Normal Stiffness Direct Shear
This paper describes the experimental component of an extensive investigation into the shear behavior of joints formed between concrete or cement grout and soft, weak or weathered rock. Understanding the behavior of such joints is important for the prediction of performance of a diverse range of structural elements, such as drilled piers socketed into rock, rock anchors, and dam foundations. The particular tests described in this paper were carried out on joints formed between concrete and an artificial silstone called Johnstone, under conditions of constant normal stiffness, and involved a range of boundary conditions and interface profiles. Interfaces included a series of regular triangular asperities and irregular profiles based on fractal geometry concepts. The authors have included the complete suite of test results in the belief that it will be a significant addition to the literature, which currently contains very few results of constant normal stiffness tests. It also demonstrates the importance of realistically modelling interface roughness. Careful observations made during testing using time-lapse photography have aided in the development of a number of simple theoretical models of behavior, which are published elsewhere.