JOURNAL OF ROCK MECHANICS

JOURNAL OF ROCK MECHANICS

Fracture analysis of rock-type U-notched components using single edge U-notched beam (SEUNB) sample

Document Type : Original Article

Authors
Javad Akbardoost
Roya Atashzay
Mechanical Engineering Department, Engineering Faculty, Kharazmi University, Tehran, Iran
10.22034/irsrm.2024.42024.1112
Abstract
Flaws, cracks, slits and other geometrical discontinuities which play as stress raiser, are among the inherent characteristics of rock masses. Due to existence of these defects, the load bearing capacity of rock masses reduces significantly. Thus, the fracture of rock masses containing geometrical discontinuities should be assessed. Some of slits on the rock components can be considered as a U-shaped notch and therefore, the assessment of rock-type U-notched sample is essential. In this paper, the in-plane shear mode (pure mode II) fracture behavior of rock part containing U-shaped notch is investigated experimentally and theoretically. Since there are some problems in generating and testing the circular shaped samples, in this study, a new test configuration based on a rectangular beam is proposed. The sample investigated in this study is the single edge U-notched beam (SEUNB) specimen which is loaded under skew-symmetric four-point bending. Determining the notch stress intensity factors (NSIF) via finite element method for SEUNB shows that the mode I NSIF is zero and hence pure mode II is achieved. Using two stress-based criteria (maximum tangential stress (MTS) and mean stress (MS) criteria) utilized extensively for investigating the fracture behavior of notched samples, the critical NSIF which represents the fracture resistance of notched samples, is predicted for each tested sample. The comparison between the experimental results and theoretical predictions demonstrates that both fracture criteria are able to predict the mode II fracture resistance of rock U-notched samples in an acceptable range for practical engineering project in the field of rock mechanics.
Keywords
Rock fracture mechanics
U-shaped notch
Pure mode II
MTS criterion
MS criterion
Subjects
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JOURNAL OF ROCK MECHANICS
Volume 8, Issue 1
Spring 2024
Pages 23-36