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Geomechanics and Engineering
  Volume 24, Number 4, February25 2021 , pages 349-358
DOI: https://doi.org/10.12989/gae.2021.24.4.349
 


Estimation of tensile strength and moduli of a tension-compression bi-modular rock
Jiong Wei, Jingren Zhou, Jae-Joon Song, Yulong Chen and Pinnaduwa H.S.W. Kulatilake

 
Abstract
    The Brazilian test has been widely used to determine the indirect tensile strength of rock, concrete and other brittle materials. The basic assumption for the calculation formula of Brazilian tensile strength is that the elastic moduli of rock are the same both in tension and compression. However, the fact is that the elastic moduli in tension and compression of most rocks are different. Thus, the formula of Brazilian tensile strength under the assumption of isotropy is unreasonable. In the present study, we conducted Brazilian tests on flat disk-shaped rock specimens and attached strain gauges at the center of the disc to measure the strains of rock. A tension-compression bi-modular model is proposed to interpret the data of the Brazilian test. The relations between the principal strains, principal stresses and the ratio of the compressive modulus to tensile modulus at the disc center are established. Thus, the tensile and compressive moduli as well as the correct tensile strength can be estimated simultaneously by the new formulas. It is found that the tensile and compressive moduli obtained using these formulas were in well agreement with the values obtained from the direct tension and compression tests. The formulas deduced from the Brazilian test based on the assumption of isotropy overestimated the tensile strength and tensile modulus and underestimated the compressive modulus. This work provides a new methodology to estimate tensile strength and moduli of rock simultaneously considering tension-compression bi-modularity.
 
Key Words
    Brazilian test; tensile modulus; compressive modulus; tension-compression bi-modular rock; indirect tensile strength
 
Address
Jiong Wei: Department of Engineering Mechanics and CNMM, School of Aerospace Engineering, Tsinghua University,
NO. 30, Shuangqing Road, Haidian District, Beijing, Republic of China

Jingren Zhou: State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resources and Hydropower, Sichuan University, No.24 South Section 1, Yihuan Road, Chengdu, Republic of China

Jae-Joon Song:Department of Energy Resources Engineering, Research Institute of Energy and Resources, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea

Yulong Chen: State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology,
Ding No.11 Xueyuan Road, Haidian District, Beijing, Republic of China

Pinnaduwa H.S.W. Kulatilake: School of Resources and Environmental Engineering, Jiangxi University of Science and Technology, No.86, Hongqi Avenue, Ganzhou, Republic of China

 

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