Abstract
The geometrical and mechanical properties of non-persistent joints as well as the mechanical behavior of intact rock (rock bridges) are significantly effective in the shear strength of weakness planes containing non-persistent joints. Therefore, comprehensive knowledge of the shear mechanism of both joints and rock bridges is required to assess the shear strength of the planes. In this study, the shear behavior of specimens containing a single non-persistent rough joint is investigated. A novel procedure was used to prepare cast specimens embedding a non-persistent (disc-shaped) rough joint using 3D printing and casting technology, and the shear strength of the specimens was examined through an extensive direct shear testing program under constant normal load (CNL) condition. Three levels for three different variables of the joint roughness, rock bridge ratio, and normal stress were considered, and the effects of these factors on the shear behavior of prepared samples were tested. The experimental results show a clear influence of the three variables on the shear strength of the specimens. The results show that the normal stress applied to the jointed zone of weakness planes is considerable, and thus joint friction contribution should be taken into account during shear strength evaluation. Furthermore, the dilation mechanism of the specimens before and after failure was investigated through a digital image correlation analysis. Finally, a camcorder was used to analyze the location and sequence of the initiated cracks.
Highlights
When the engineering dimensions of an investigated site exceed the average joint size in the domain, the joints are surrounded by intact rock in the rock mass and should be considered as non-persistent
This study investigates the shear behavior of specimens with an embedded nonpersistent rough joint using a direct shear test machine under constant normal load (CNL)
This study investigates the effects of three variables (rock bridge ratio (ζ), normal stress, and joint roughness (Z2)) on the shear behavior of plaster specimens with a single non-persistent joint
Summary
When the engineering dimensions of an investigated site exceed the average joint size in the domain, the joints are surrounded by intact rock (rock bridge) in the rock mass and should be considered as non-persistent. Joint size (persistence) should be precisely measured during the field survey owing to its substantial influence on the rock mass strength [1]. A combined shear plane where failure occurs is usually formed by the interaction of various non-persistent joints. Deng and Zhang [2] and Segall and Pollard [3] noted that the rupture of rock bridges connecting en-echelon joints may lead to the development of faults. The bridges and the joints have a significant effect on the shear behavior of the failure paths [5,6]
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