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Effects of loading conditions on strength and deformability of fractured rocks - A numerical study
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Engineering Geology and Geophysics Research Group)
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Engineering Geology and Geophysics Research Group)
2014 (English)In: Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium, Taylor & Francis Group, 2014, 365-368 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents a systematic numerical study to evaluate the effects of two different loading conditions, namely the axial stress and axial velocity, on testing compressive strength and deformability properties of fractured rocks. The UDEC code was used to perform a series of numerical tests on two-dimensional fracture network (DFN) models, in the similar ways for the uniaxial and biaxial laboratory testing on intact rock samples. The obtained stresses and strains from these numerical experiments were used to estimate equivalent directional Young's modulus and fit the Mohr-Coulomb and Hoek-Brown failure criteria, represented by equivalent material properties defining these two criteria. The numerical results show that stress-strain behaviors changes by loading conditions with higher averaged axial stress under axial velocity condition than that under axial stress condition. Therefore, the effects of different loading conditions should be carefully considered for designing and interpretation of results for in-situ experiments with large volumes of fractured rocks.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2014. 365-368 p.
Keyword [en]
Compressive strength, Deformation, Elastic moduli, Elasticity, Experiments, Fracture testing, Rock mechanics, Stress analysis, Structural design, Deformability properties, Equivalent material properties, Hoek-Brown failure, In-situ experiments, Laboratory testing, Numerical experiments, Numerical results, Stress-strain behaviors
National Category
Geology
Identifiers
URN: urn:nbn:se:kth:diva-146696DOI: 10.1201/b16955-60ISI: 000345985300056Scopus ID: 2-s2.0-84901344637ISBN: 978-1-138-00149-7 (print)OAI: oai:DiVA.org:kth-146696DiVA: diva2:724896
Conference
2014 ISRM European Regional Symposium on Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, EUROCK 2014, Vigo, Spain, 26 May 2014 through 28 May 2014
Note

QC 20150108

Available from: 2014-06-13 Created: 2014-06-13 Last updated: 2015-01-08Bibliographically approved
In thesis
1. Strength and deformability of fractured rocks
Open this publication in new window or tab >>Strength and deformability of fractured rocks
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents a systematic numerical modeling framework to simulate the stress-deformation and coupled stress-deformation-flow processes by performing uniaxial and biaxial compressive tests on fractured rock models with considering the effects of different loading conditions, different loading directions (anisotropy), and coupled hydro-mechanical processes for evaluating strength and deformability behavior of fractured rocks. By using code UDEC of discrete element method (DEM), a series of numerical experiments were conducted on discrete fracture network models (DFN) at an established representative elementary volume (REV), based on realistic geometrical and mechanical data of fracture systems from field mapping at Sellafield, UK. The results were used to estimate the equivalent Young’s modulus and Poisson’s ratio and to fit the Mohr-Coulomb and Hoek-Brown failure criteria, represented by equivalent material properties defining these two criteria.

The results demonstrate that strength and deformation parameters of fractured rocks are dependent on confining pressures, loading directions, water pressure, and mechanical and hydraulic boundary conditions. Fractured rocks behave nonlinearly, represented by their elasto-plastic behavior with a strain hardening trend. Fluid flow analysis in fractured rocks under hydro-mechanical loading conditions show an important impact of water pressure on the strength and deformability parameters of fractured rocks, due to the effective stress phenomenon, but the values of stress and strength reduction may or may not equal to the magnitude of water pressure, due to the influence of fracture system complexity. Stochastic analysis indicates that the strength and deformation properties of fractured rocks have ranges of values instead of fixed values, hence such analyses should be considered especially in cases where there is significant scatter in the rock and fracture parameters. These scientific achievements can improve our understanding of fractured rocks’ hydro-mechanical behavior and are useful for the design of large-scale in-situ experiments with large volumes of fractured rocks, considering coupled stress-deformation-flow processes in engineering practice. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xvi, 97 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; 2014:07
Keyword
Fractured crystalline rocks, Numerical experiments, Discrete element methods (DEM), Discrete fracture network (DFN), Representative elementary volume (REV), Coupled hydro-mechanical processes, Anisotropy, Effective stress, Failure criteria, Stochastic realizations
National Category
Engineering and Technology
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-155719 (URN)978-91-7595-324-3 (ISBN)
Public defence
2014-11-25, F3, Lindstedsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20141111

Available from: 2014-11-11 Created: 2014-11-10 Last updated: 2014-11-11Bibliographically approved

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Citation style
  • apa
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