Page 93 - Applied Petroleum Geomechanics

CHAPTER 3

Rock strengths and rock failure

criteria

Contents

3.1 Laboratory tests for rock strengths 86
3.1.1 Uniaxial tensile test 87
3.1.2 Uniaxial compression test 88
3.1.3 Triaxial compression test and rock peak strengths 91
3.1.4 Polyaxial compression test 94
3.2 Rock strengths from petrophysical and well log data 94
3.2.1 Empirical equations of rock strengths in shales 95
3.2.1.1 From sonic velocity 95
3.2.1.2 From porosity 96
3.2.1.3 From Young’s modulus 98
3.2.2 Empirical equations of rock strengths in sandstones 100
3.2.2.1 From sonic velocity and transit time 100
3.2.2.2 From Young’s modulus and porosity 102
3.2.3 Empirical equations of rock strengths in carbonate rocks 103
3.2.3.1 From sonic velocity 103
3.2.3.2 From Young’s modulus and porosity 104
3.2.4 Field methods for estimating rock uniaxial compressive strength 105
3.3 Rock strength anisotropy 105
3.4 Rock failure criteria 108
3.4.1 Rock failure types 108
3.4.2 MohreCoulomb failure criterion 109
3.4.2.1 Linear MohreCoulomb failure criterion 109
3.4.2.2 Modified MohreCoulomb failure criterion 114
3.4.3 Weak plane sliding failure criterion 117
3.4.4 DruckerePrager failure criterion 119
3.4.5 Modified Lade failure criterion 121
3.4.6 HoekeBrown failure criterion 122
3.4.7 True triaxial failure criterion 122
3.4.8 Cam-Clay failure criterion 124
3.4.9 Tensile and Griffith failure criteria 126
References 128

Abstract
Laboratory test methods are introduced to determine stressestrain relationships and
rock strengths. Rock failure mechanisms are studied based on uniaxial and triaxial

Applied Petroleum Geomechanics
ISBN 978-0-12-814814-3 Copyright © 2019 Elsevier Inc.
https://doi.org/10.1016/B978-0-12-814814-3.00003-4 All rights reserved. 85