An anisotropic damage model for rock

 

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dc.contributor.advisor Scheele, Friedrich en_ZA
dc.contributor.author Sellers, E J en_ZA
dc.date.accessioned 2016-08-24T12:51:25Z
dc.date.available 2016-08-24T12:51:25Z
dc.date.issued 1994 en_ZA
dc.identifier.citation Sellers, E. 1994. An anisotropic damage model for rock. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/21488
dc.description Bibliography: pages 146-155. en_ZA
dc.description.abstract An anisotropic damage model is proposed for the constitutive description of microcracking processes in brittle rock under a general loading path. Experimental data and micromechanical models are reviewed to quantify the effect of microcracking on the material stiffness and the mechanisms of microcrack formation in brittle rocks under compression are discussed. The sliding crack concept is adopted as the micromechanical basis of the anisotropic damage model. Undamaged material is represented with a linear elastic constitutive equation. Damage initiation is defined by a Coulomb friction law, which excludes damage at low deviatoric stress levels. The formulation of the directional damage extends the arguments of continuum damage models for tension cracking to general, tension and compression, stress states. This is achieved by the definition of damage in a subdomain of the total strain and the characterisation of the directional microcracking by a fourth order tensor internal variable, the damaged secant stiffness of the 'crack' strain subdomain. Induced anisotropy results from the reduction of components of the initial stiffness tensor in the direction of the positive principal 'crack' strains. Evolution of the damage magnitude is determined by the principle of maximum damage dissipation in terms of the undamaged energy norm of the positive part of the 'crack' strain tensor. Versatile evolution functions, based on the Weibull probability density function, are proposed for compression and extension damage modes. Unloading and reloading criteria are developed which are consistent with the sliding crack concept and introduce hysteretic behaviour. A numerical solution scheme is presented and the model is implemented in a nonlinear finite element program. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Civil Engineering en_ZA
dc.title An anisotropic damage model for rock en_ZA
dc.type Doctoral Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Engineering and the Built Environment
dc.publisher.department Department of Civil Engineering en_ZA
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Sellers, E. J. (1994). <i>An anisotropic damage model for rock</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Civil Engineering. Retrieved from http://hdl.handle.net/11427/21488 en_ZA
dc.identifier.chicagocitation Sellers, E J. <i>"An anisotropic damage model for rock."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Civil Engineering, 1994. http://hdl.handle.net/11427/21488 en_ZA
dc.identifier.vancouvercitation Sellers EJ. An anisotropic damage model for rock. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Civil Engineering, 1994 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/21488 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Sellers, E J AB - An anisotropic damage model is proposed for the constitutive description of microcracking processes in brittle rock under a general loading path. Experimental data and micromechanical models are reviewed to quantify the effect of microcracking on the material stiffness and the mechanisms of microcrack formation in brittle rocks under compression are discussed. The sliding crack concept is adopted as the micromechanical basis of the anisotropic damage model. Undamaged material is represented with a linear elastic constitutive equation. Damage initiation is defined by a Coulomb friction law, which excludes damage at low deviatoric stress levels. The formulation of the directional damage extends the arguments of continuum damage models for tension cracking to general, tension and compression, stress states. This is achieved by the definition of damage in a subdomain of the total strain and the characterisation of the directional microcracking by a fourth order tensor internal variable, the damaged secant stiffness of the 'crack' strain subdomain. Induced anisotropy results from the reduction of components of the initial stiffness tensor in the direction of the positive principal 'crack' strains. Evolution of the damage magnitude is determined by the principle of maximum damage dissipation in terms of the undamaged energy norm of the positive part of the 'crack' strain tensor. Versatile evolution functions, based on the Weibull probability density function, are proposed for compression and extension damage modes. Unloading and reloading criteria are developed which are consistent with the sliding crack concept and introduce hysteretic behaviour. A numerical solution scheme is presented and the model is implemented in a nonlinear finite element program. DA - 1994 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1994 T1 - An anisotropic damage model for rock TI - An anisotropic damage model for rock UR - http://hdl.handle.net/11427/21488 ER - en_ZA


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