PSI - Issue 39

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ScienceDirect

Procedia Structural Integrity 39 (2022) 792–800 Structural Integrity Procedia 00 (2019) 000–000 Structural Integrity Procedia 00 ( 019) 000– 00

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of CP 2021 – Guest Editors Abstract We evaluate the accuracy of two well-known fracture growth theories in predicting crack growth path in anisotropic rocks, through comparison with new experimental data. In doing so, the results of fracture toughness tests on metamorphic Grimsel Granite under four different ratios of mixed-mode I/II loadings are reported, and the experimental kink angle and the effective fracture toughness are compared with the predictions of the maximum tangential stress (MTS), and the maximum energy release rate (MERR) criteria. Comparing theoretical predictions based on the classical forms of the two criteria with the experimental data reveals that the energy-based criterion is unable to accurately describe the fracture growth behavior. We suggest a reformulation of the MERR criterion and show that the modified form give significantly better predictions of fracture growth trajectories. The evaluation of these criteria also illustrates that the MTS and modified MERR criteria cannot provide accurate predictions if T-stress is absent. c 2020 The Authors. Published by Elsevier B.V. his is an open access article under the CC BY-NC-ND license (http://creativec mmons.org/licenses/by-nc-nd/4.0/) P r-review under responsibility of CP 2021 – Guest Editors. Keywords: Type your keywords here, separated by semicolons ; Fracture growth criteria; Mixed-mode I / II; Anisotropic rocks; T-stress Abstract We evaluate the accuracy of two well-known fracture growth theories in predicting crack growth path in anisotropic rocks, through comparison with new experimental data. In doing so, the results of fracture toughness tests on metamorphic Grimsel Granite under four different ratios of mixed-mode I/II loadings are reported, and the experimental kink angle and the effective fracture toughness are co pared with the predictions of the maximum tangential stress (MTS), and the maximum energy release rate (MERR) criteria. Comparing theoretical predictions based on the classical forms of the two criteria with the experimental data reveals that the energy-based criterion is unable to accurately describe the fracture growth behavior. We suggest a reformulation of the MERR criterion and show that the modified form give significantly better predictions of fracture growth trajectories. The evaluation of these criteria also illustrates that the MTS and modified MERR criteria cannot provide accurate predictions if T-stress is absent. c 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of CP 2021 – Guest Editors. Keywords: Type your keywords here, separated by semicolons ; Fracture growth criteria; Mixed-mode I / II; Anisotropic rocks; T-stress 7th International Conference on Crack Paths On Reliable Prediction of Fracture Path in Anisotropic Rocks Mahsa Sakha a, ∗ , Morteza Nejati a , Ali Aminzadeh a , Saeid Ghouli b , Martin O. Saar c,d , Thomas Driesner a a Department of Earth Sciences, ETH Zurich, Switzerland 7th International Conference on Crack Paths On Reliable Prediction of Fracture Path in Anisotropic Rocks Mahsa Sakha a, ∗ , Morteza Nejati a , Ali Aminzadeh a , Saeid Ghouli b , Martin O. Saar c,d , Thomas Driesner a a Department of Earth Sciences, ETH Zurich, Switzerland b School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran c Geothermal Energy and Geofluids Group, Department of Earth Sciences, ETH Zurich, Switzerland d Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, USA b School of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran c Geothermal Energy and Geofluids Group, Department of Earth Sciences, ETH Zurich, Switzerland d Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, USA

1. Introduction 1. Introduction

Hydraulic fracturing is the formation of fracture network in a rock mass in response to injection of high-pressure fluid. As the result, this process increases the rock mass fluid conductivity in low-permeable rocks by creating new fractures and/or inducing shear slip on pre-existing fractures and faults (hydro-shearing) (He et al., 2016). This ap proach has widely been used in many projects such as enhanced geothermal systems, shale oil and gas, carbon seques tration, wastewater injection, mining etc. (Peirce, 2015). The main goal of hydraulic fracturing in all these industries is to enhance permeability of the systems by creating effective fracture networks in the host rocks. Usually hydraulic fracturing is performed in formations where the material exhibits anisotropy in the mechanical properties. The pres- Hydraulic fracturing is the formation of fracture network in a rock mass in response to injection of high-pressure fluid. As the result, this process increases the rock mass fluid conductivity in low-permeable rocks by creating new fractures and/or inducing shear slip on pre-existing fractures and faults (hydro-shearing) (He et al., 2016). This ap proach has widely been used in many projects such as enhanced geothermal systems, shale oil and gas, carbon seques tration, wastewater injection, mining etc. (Peirce, 2015). The main goal of hydraulic fracturing in all these industries is to enhance permeability of the systems by creating effective fracture networks in the host rocks. Usually hydraulic fracturing is performed in formations where the material exhibits anisotropy in the mechanical properties. The pres-

2452-3216 © 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of CP 2021 – Guest Editors 10.1016/j.prostr.2022.03.152 ∗ Corresponding author. Tel.: +4-144-632-8019. E-mail address: mahsa.sakha@erdw.ethz.ch 2210-7843 c 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of CP 2021 – Guest Editors. ∗ Corresponding author. Tel.: +4-144-632-8019. E-mail address: mahsa.sakha@erdw.ethz.ch 2210-7843 c 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of CP 2021 – Guest Editors.