Study on particle size effects on strength and crack coalescence behavior of rock during Brazilian splitting test

Yanhua Huang, Shengqi Yang, Yang Ju, Xiaoping Zhou, Jian Zhao

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A discrete element disc specimen model was constructed using a set of microscopic parameters which were calibrated by the experimental results of intact rock-like material disc specimen during Brazilian splitting test in particle flow code (PFC).Then PFC was adopted to simulate Brazilian test for central straight notched Brazilian disc (CSNBD) specimens. The effects of particle size on the load-displacement curves, tensile strength and failure mode of CSNBD specimens were analyzed, and the evolution laws of meso-force, micro-crack and energy during the process of macrocrack initiation, propagation and coalescence of CSNBD specimen were revealed. The results show that complete axial load-displacement curves can be divided into three types, i.e., single peak(type I), softening after first-peak(type II) and hardening after first-peak(type III).Compared with the intact disc specimen, the tensile strength of CSNBD specimen all decreases, and the reducing extent is related to the notch angle and particle size. By keeping the notch angle constant, the tensile strength shows a downwards trend with the increase of particle size, while keeping the particle size constant, the tensile strength decreases with the increase of the notch angle. The failure modes of CSNBD specimens are dependent on particle size. The particle size mainly affects the initiation and propagation of secondly cracks. The power produced by boundary wall is firstly used to overcome the bond among particles. After the crack initiation, friction energy begins to work, and the crack is propagated by strain energy. Since the particle moves slowly, the kinetic energy is small. The boundary energy is positively correlated with the tensile strength, i.e., the bigger boundary, the higher tensile strength.

Original languageEnglish
Pages (from-to)1272-1281
Number of pages10
JournalJournal of Central South University (Science and Technology)
Issue number4
Publication statusPublished - 26 Apr 2016


  • Brazilian test
  • Central straight notched disc specimen
  • Particle flow code
  • Particle size effect
  • Rock mechanics

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