JOURNAL OF ROCK MECHANICS

JOURNAL OF ROCK MECHANICS

Experimental and Numerical Investigation of Conventional Methods for Determining Mode I Fracture Toughness of Concrete

Document Type : Original Article

Authors
Mohammad Reza Abroshan 1
Majid Noorian-Bidgoli 1
Hadi Haeri 2
1 Department of Mining Engineering, Faculty of Engineering, University of Kashan, Iran
2 Department of Mining Engineering, Higher Education Complex of Zarand, Shahid Bahonar University of Kerman, Kerman, Iran
10.22034/irsrm.2025.543623.1056
Abstract
Fracture toughness is one of the most important mechanical properties of rock-like materials and plays a decisive role in the stability analysis of concrete and rock structures. In recent years, the International Society of Rock Mechanics (ISRM) has proposed several standardized specimen geometries, including SCB, CB, CCNBD, and SR, to determine Mode I fracture toughness. However, numerous reports have shown that the values obtained from these methods are not consistent, with significant differences between them. In this study, to investigate this issue in detail, a series of laboratory tests were designed and performed on standard concrete samples to determine their fracture toughness values. The experimental results showed that the fracture toughness values are highly dependent on the specimen geometry. For concrete with a strength of 30 MPa, the highest toughness value was obtained for the CCNBD specimen at 0.43 MPa•m⁰•⁵, while the lowest value was obtained for the SCB specimen at 0.34 MPa•m⁰•⁵. This represents a difference of approximately 26.4 percent. Additionally, three-dimensional numerical modeling was performed using the Discrete Element Method (DEM) in the YADE software. Prior to simulating the fracture tests, the model's microscopic parameters were calibrated based on uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) tests. The numerical results from simulating the different geometries showed that the discrete element model can accurately reproduce both the fracture toughness values and the fracture patterns. The difference between the experimental and numerical data for all geometries was less than 2 to 3 percent. The findings of this study indicate that the choice of test geometry has a direct and significant effect on the measured fracture toughness value. Furthermore, numerical modeling has been demonstrated to be an efficient tool for interpreting and analyzing these differences.
Keywords
Fracture toughness
SCB CB CCNBD CNSRB samples
Numerical modeling
Discrete element method (DEM)
Fracture Mechanism
Rock-like materials
Subjects
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JOURNAL OF ROCK MECHANICS
Volume 9, Issue 1
Spring 2025
Pages 25-45