Abstract

To investigate the tensile properties of brittle rock with microdamage, an indirect tensile test was conducted. High-speed image acquisition and acoustic emission (AE) were applied to record the process. After the tests, the images were analysed using the digital image correlation (DIC) method to obtain the stress and strain development of the rock under tension. The damage constitutive model was also developed in this study. Based on known and assumed statistical distributions for microcracks and the theory of fracture and statistical damage, the mechanical properties and failure mechanisms of brittle rock under tension were analysed. The basic statistical parameters of the main cracks in the elements were described, and the damage variable was defined to develop the effective modulus. A constitutive model for microdamage brittle rock-like materials was established based on the effective modulus. Additionally, to describe the crack propagation, a random-direction crack under tension was analysed to calculate the crack-tip stress intensity factor. After applying the basic parameters of the sandstone to the analytical model, the results showed that the analytical model agreed with the experimental results.

Highlights

  • As a natural solid material, generally composed of various mineral grains, cement, and pores, rock contains natural defects such as cracks and joints that are discontinuous, nonuniform, nonlinear, and anisotropic

  • Macroscopic analysis is based on continuum mechanics and aims to study the macroscopic behaviours of rock. e mesoscopic method is used to study the macroscopic mechanical behaviour caused by the generation and development of microcracks in rock

  • A high-speed (1000 frames/sec) camera (Figure 2) was placed in front of the sample’s speckled surface, and it collected images showing the development of the deformation and fracture of the specimens with speckled surfaces, which could subsequently be analysed by means of digital image correlation (DIC) to show the deformation and strain field

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Summary

Introduction

As a natural solid material, generally composed of various mineral grains, cement, and pores, rock contains natural defects such as cracks and joints that are discontinuous, nonuniform, nonlinear, and anisotropic. E mesoscopic method is used to study the macroscopic mechanical behaviour caused by the generation and development of microcracks in rock. For materials with natural defects, such as rock, damage and its generation and development are microscopic phenomena, but the influence will result in macroscopic mechanical behaviours [22,23,24,25]. Is research made an important contribution, and a damage constitutive model was developed based on Weibull distribution, and the effect of model parameters on deformation characteristic after stress-temperature cycling was discussed [41]. Based on the simplified characteristics of microcracks in sandstone, we present a microcrack damage model, proposing a constitutive model for brittle rock-like materials under tension that uses the Griffith strength criterion. After applying the basic parameters of the sandstone into the model, the verification of theoretical damage constitutive model by comparing the results of Brazilian disk tensile test should be added to fully introduce the work in this paper, and the results are discussed in the end

Indirect Tensile Test
Construction of the Damage Model
Results and Discussion
Conclusions
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