Microstructural investigation of subcritical crack propagation and Fracture Process Zone (FPZ) by the reduction of rock fracture toughness under cyclic loading

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Tarih

2016

Dergi Başlığı

Dergi ISSN

Cilt Başlığı

Yayıncı

Elsevier Science Bv

Erişim Hakkı

info:eu-repo/semantics/closedAccess

Özet

This study presents the results of laboratory diametrical compression tests performed on Brisbane tuff disc specimens to develop much-needed understanding of the micro-mechanical and micro-structural dynamics of sub critical crack propagation. The strength variation in rocks under mechanical loading without corrosive chemical environment was investigated by investigating the mode-I (tensile) fracture toughness (K-IC) response to static and cyclic loading. In some cases, cracks can grow at a lower load level compared to the static case. This phenomenon is called subcritical crack propagation and depends on,the behaviour of the Fracture Process Zone (FPZ). The K-IC response to cyclic loading was found to be different from that under static loading in terms of the ultimate load and the damage mechanisms in front of the chevron crack. A maximum reduction of the static K-IC of 43% was obtained for the highest amplitude increasing cyclic loading test. Detailed Scanning Electron Microscope (SEM) examinations were performed on the surfaces of the tips of the chevron notch cracks, revealing that both loading methods cause fatigue in the disc rock specimens. When compared with static rupture, the main difference with the cyclically loaded specimens was that intergranular cracks were formed due to particle failure under cyclic loading, while smooth and bright cracks along cleavage planes were formed under static loading. It is believed in this study that the rock texture characteristics such as interlocked and cemented grains, cement volume, cement mineralogy play very important role on damage behaviour of rocks and development of FPZ and subcritical cracking. (C) 2016 Elsevier B.V. All rights reserved.

Açıklama

Anahtar Kelimeler

Subcritical crack, Fracture Process Zone (FPZ), Rock fracture toughness, Rock fatigue, CCNBD

Kaynak

Engineering Geology

WoS Q Değeri

Q1

Scopus Q Değeri

Q1

Cilt

208

Sayı

Künye