Scale effects on triaxial peak and residual strength of granite and preliminary PFC3D models
Xian Estévez-Ventosa,Uxía Castro-Filgueira,Manuel A. González-Fernández,Fernando García-Bastante,Diego Mas-Ivars,Leandro R. Alejano
Abstract
Research studies on the scale effect on triaxial strength of intact rocks are scarce, being more common those in uniaxial strength. In this paper, the authors present and briefly interpret the peak and residual strength trends on a series of triaxial tests on different size specimens (30 mm to 84 mm diameter) of an intact granitic rock at confinements ranging from 0 to 15 MPa. Peak strength tends to grow from smaller to standard-size samples (54 mm) and then diminishes for larger values at low confinement. However, a slight change in strength is observed at higher confinements. Residual strength is observed to be much less size-dependent. Additionally, this study introduces preliminary modelling approaches of these laboratory observations with the help of three-dimensional particle flow code (PFC3D) simulations based on bonded particle models (BPM). Based on previous studies, two modelling approaches have been followed. In the first one, the maximum and minimum particle diameter (Dmax and Dmin) are kept constant irrespective of the sample size, whereas in the second one, the resolution (number of particles within the sample or v) was kept constant. Neither of these approaches properly represent the observations in actual laboratory tests, even if both of them show some interesting capabilities reported in this document. Eventually, some suggestions are provided to proceed towards improving modelling approaches to represent observed scale effects.
Xian Estévez-Ventosa, Uxía Castro-Filgueira, Manuel A. González-Fernández,Fernando García-Bastante and Leandro R. Alejano — CINTECX, GESSMin group, Department of Natural Resources and Environmental Engineering, University of Vigo, Campus Lagoas, Vigo, Pontevedra, 36.310, Spain
Diego Mas-Ivars — Swedish Nuclear Fuel and Waste Management Company (SKB), Evenemangsgatan 13, Box 3091, SE-169 03 Solna, Stockholm, Sweden; Division of Soil and Rock Mechanics, Royal Institute of Technology (KTH), Brinellvägen 23, 100 44 Stockholm, Sweden
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