Instrumentation of Large Scale Direct Shear Test to Study the Progressive Failure of Concrete/Rock Interface

Mouzannar, Hussein; Bost, Marion; Joffrin, Patrick; Pruvost, Christophe; Rojat, Fabrice; Blache, Jacques; Houel, Adrien; Valade, Michel; Khadour, Aghiad; Chataigner, Sylvain; Gaillet, Laurent; David, Jean-François; Falaise, Yannick; Quiertant, Marc

doi:10.1007/978-94-024-0867-6_91

“…To study thoroughly the shear behaviour of concrete-rock interface and to observe possible cracking mechanisms and debonding propagation along this interface, different instrumentation devices were utilized during the large scale direct shear tests, set up both within the samples and on their lateral sides (Mouzannar et al, 2016). Strain gauges and acoustic emission (AE) sensors were installed on the lateral sides of concrete parts, close to the interfaces (Fig.…”

Section: Instrumentationmentioning

confidence: 99%

“…After peak 2, the stress relaxation observed in the strain gauges V1 to V3 is consistent with the previous explanation of a residual behaviour. At different steps of the shear test, the AE data analysis enabled the 2D localization of the acoustic events in a plane parallel to the shear plane and in parallel, the 2D strain distributions in the concrete close to the interface were extrapolated from the measurements of the optical fiber (Mouzannar et al, 2016). Before peak 1, the AE events were concentrated on the opposite-to-push side (Fig.…”

Section: Shear Behaviour Of the Concrete-rock Interface For The Samplmentioning

confidence: 99%

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

Bost

¹

,

Mouzannar

²

,

Rojat

³

et al. 2019

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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.

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

Bost

¹

,

Mouzannar

²

,

Rojat

³

et al. 2020

KSCE Journal of Civil Engineering

View full text Add to dashboard Cite

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.

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A Shear Device with Controlled Boundary Conditions for Very Large Nonplanar Rock Discontinuities

Jeffery

¹

,

Crumpton

²

,

Fityus

³

et al. 2022

Geotechnical Testing Journal

3

0

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The shear strength of rock discontinuities is an important design parameter that is noted to be scale dependent. Historically, discontinuity shear strength and scale dependency studies have used small to medium size laboratory shear devices that accommodate specimens with a relatively small area (0.01 to 1 m2) compared to real discontinuities. In the literature, there is a limited amount of shear strength studies available on discontinuity surfaces with areas of several square meters. This is inherently linked to the challenging nature of performing large shear tests. As shear strength scale dependency is still a timely topic, there is still a need for conducting large scale direct shear tests to support research. To facilitate investigations into the shear response of large discontinuities, a very large shear device was designed and built at the University of Newcastle, Australia. The device is designed to accommodate 2 m by 2 m specimens and restrict rotation and translations of the top surface during shearing. This article presents the design and characteristics of the shear device, the process undertaken to create 2 m by 2 m mortar discontinuity replicas and the experimental results of the first series of direct shear tests conducted. The experimental results confirm the systems design for restricting undesired translations and rotations of the tested specimen surfaces and test repeatability.

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Instrumentation of Large Scale Direct Shear Test to Study the Progressive Failure of Concrete/Rock Interface

Cited by 3 publications

References 2 publications

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

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

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

A Shear Device with Controlled Boundary Conditions for Very Large Nonplanar Rock Discontinuities

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