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Scale effects on triaxial peak and residual strength of granite and preliminary PFC3D models

  • Xian, Estevez-Ventosa (CINTECX, GESSMin group, Department of Natural Resources and Environmental Engineering, University of Vigo, Campus Lagoas) ;
  • Uxia, Castro-Filgueira (CINTECX, GESSMin group, Department of Natural Resources and Environmental Engineering, University of Vigo, Campus Lagoas) ;
  • Manuel A., Gonzalez-Fernandez (CINTECX, GESSMin group, Department of Natural Resources and Environmental Engineering, University of Vigo, Campus Lagoas) ;
  • Fernando, Garcia-Bastante (CINTECX, GESSMin group, Department of Natural Resources and Environmental Engineering, University of Vigo, Campus Lagoas) ;
  • Diego, Mas-Ivars (Swedish Nuclear Fuel and Waste Management Company (SKB)) ;
  • Leandro R., Alejano (CINTECX, GESSMin group, Department of Natural Resources and Environmental Engineering, University of Vigo, Campus Lagoas)
  • Received : 2021.11.10
  • Accepted : 2022.11.15
  • Published : 2022.12.10
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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 ϕv) 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.

Keywords

Acknowledgement

The authors acknowledge the Spanish Ministry of Science and Innovation for funding this study as part of the project awarded under Contract Reference No. RTI2018-093563-B-I00, partially financed by means of ERDF funds from the EU. Itasca Consulting Group is acknowledged for inviting the second author in their Itasca Education Partnership Program, which provides her with the PFC program.

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