Metric Scale Study of the Bonded Concrete-Rock Interface Shear Behaviour

Abstract

The shear strength of concrete-rock interface is a key factor to evaluate the stability of gravity dams. The shear strength assessment by achieving tests on small samples gives values different from those estimated by back-analysis on the existing dams. This work aims to study the shear behaviour of concrete-rock interface in the metric scale. Five direct shear tests were performed on bonded meterscale concrete-granite interfaces in the range of normal stresses to which gravity dam foundation is subjected. Specific instrumentation were installed to monitor the failure mechanisms during the tests. The five concrete-rock interfaces have not broken by shearing of materials (concrete, rock) in the shear plane imposed by the test device, but by debonding of the contact between concrete and rock. Considering roughness of the contact surface in the decimeter scale and the results of shear tests carried out in the same scale, the decimeter scale is demonstrated to correspond to the elementary surface for the shear behaviour of the metric concrete-rock interface. According to the level of normal stress, the stiffness of both materials and the main asperities in the decimeter scale, different failure mechanisms occur locally to justify the overall failure in the metric scale.

Shear damage stress and frequency spectral characteristics of dry and saturated red sandstone determined by acoustic emission

“…3) Normal loading: The normal stresses (5,10,20,30, and 40 MPa) were applied to the predetermined stress level at the rate of 0.5 kN/s to achieve constant normal stress. 4) Tangential loading: The normal stress was maintained for each direct shear test, and the tangential force was applied at the rate of 0.005 mm/s until the sample failed.…”

“…Formulas 3and 4are the expressions of shear strength of the dry and saturated red sandstone, respectively. Formulas (5) and (6) are the expressions of shear damage stress of the dry and saturated red sandstone, respectively. Fig.…”

“…Zhao et al [4] derived the general compression shear failure criterion of the equivalent model, which considers the cohesive strength of the interface coal and soft rock. Bost et al [5] compared the shear strength in different scales and proposed an analytical model that evaluates the shear strength in the metric scale. Moradian et al [6] analyzed the count and energy parameters of the AE signals during direct shear test on different types of joints to monitor the shear behavior of the joints.…”

Prediction of Peak Friction Angle using Photogrammetry and Comparison to Shear Test Results of Metric Scale Rock Fractures

“…Roughness scaling has a widely-observed impact on joint shear as reported by Barton and Choubey 1977;Bandis et al 1981;Fardin et al 2001;Tatone and Grasselli 2013;Bahaaddini et al 2014;Johansson and Stille 2014;Johansson 2016;Bost et al 2019;Azinfar et al 2019. The results of extensive studies of the scale effects have been summarized in a number of recent research studies (Tatone and Grasselli 2013;Bahaaddini et al 2014;Azinfar et al 2019;Wang et al 2020).…”