PSI - Issue 45

Nhan T. Nguyen et al. / Procedia Structural Integrity 45 (2023) 52–59 Nguyen et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 7. Model response at 200 MPa confining pressure at the macroscopic scale and the inside/outside localised zone: (a) elastic outside volumetric response; (b) elastic outside shear response; (c) inelastic outside volumetric response and; (d) inelastic outside shear response. 4. Conclusions This paper focuses on an approach to capturing the inhomogeneous deformation in porous reservoir rocks when localised failure takes place in the form of a compaction band. The discontinuous characteristic is reflected in the strong difference between two distinguished mesoscale responses across the boundary of localisation bands where materials outside and inside these bands behave elastically and inelastically, respectively. These two local responses are connected through a kinematic enhancement with details on localisation bands (orientation, thickness) and relative size between the band thickness and the volume containing it to naturally describe the mixed-material structure and size-dependent properties of the macro response. The coupled breakage-plastic model is adopted to take into consideration the grain-crushing mechanism and its interdependence with the grain-rearrangement mechanism inside compaction bands. Some numerical results on drained triaxial test on Berea sandstone are provided to highlight the advantages of this model in reproducing the macro behaviour under effects of inhomogeneous deformation and properties of localisation bands. Nonetheless, some discrepancies between numerical and experimental data are observed. This may be because the evolution in thickness and orientation of localisation bands during loading is neglected, despite its importance in governing the macro stress-strain behaviour. Furthermore, we also acknowledge the limitation of the current calibration procedure in determining size-effect parameters ( , ℎ ) as another possible explanation for these mismatches since no consensus has been reached on measuring them. Acknowledgements Support from the Australian Research Council (ARC) and OZ Minerals Ltd through Linkage Project LP200100038 is gratefully acknowledged. References Baud, P., Klein, E., Wong, T.-F., 2004. Compaction localization in porous sandstones: spatial evolution of damage and acoustic emission activity. Journal of Structural Geology, 26 , 603-624.https://doi.org/10.1016/j.jsg.2003.09.002. Baud, P., Vajdova, V., Wong, T.-F., 2006. Shear-enhanced compaction and strain localization: Inelastic deformation and constitutive modeling of four porous sandstones. Journal of Geophysical Research: Solid Earth, 111.10.1029/2005JB004101. Baud, P., Hall, S., Heap, M.J., Ji, Y., Wong, T.-F., 2021. The Brittle-Ductile Transition in Porous Limestone: Failure Mode, Constitutive Modeling of Inelastic Deformation and Strain Localization. Journal of Geophysical Research: Solid Earth, 126 , e2020JB021602.https://doi.org/10.1029/2020JB021602. Borja, R.I., 2000. A finite element model for strain localization analysis of strongly discontinuous fields based on standard Galerkin approximation. Computer Methods in Applied Mechanics and Engineering, 190 , 1529-1549.https://doi.org/10.1016/S0045-7825(00)00176-6. Buscarnera, G., Einav, I., 2012. The yielding of brittle unsaturated granular soils. Géotechnique, 62 , 147-160, Carosio, A., Willam, K., Etse, G., 2000. On the consistency of viscoplastic formulations. International Journal of Solids and Structures, 37 , 7349 7369, Chambon, R., Crochepeyre, S., Desrues, J., 2000. Localization crit eria for non‐linear constitutive equations of geomaterials. Mechanics of Cohesive‐ frictional Materials: An International Journal on Experiments, Modelling and Computation of Materials and Structures, 5 , 61-82, Chen, Z., Schreyer, H.L., 1987. Simulation of soil-concrete interfaces with nonlocal constitutive models. Journal of Engineering Mechanics, 113 , 1665-1677.10.1061/(ASCE)0733-9399(1987)113:11(1665).

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