Numerical Quantification of Shear Band–Induced Scale Effects in Physical Models

Rescaling the performance of reduced physical models to prototype scale must account for the interaction between the tested system and finite plastic deformation zones. Although higher-order continuum models offer opportunities to quantify these effects, no study has yet assessed the impact of shear zones on the performance of reduced physical models, such as those used in geotechnical centrifuge tests. This paper investigates this problem with a gradient-type nonlocal plasticity model, specifically a hardening-softening nonassociative Mohr-Coulomb constitutive law augmented with an over-nonlocal formulation. Within this framework, a closed-form expression of the shear band thickness can be achieved. Scale effects in several geotechnical systems are then investigated numerically, including specimens subjected to plane strain compression and shallow footings. The simulations, validated against experimental data, indicate that smaller systems lead to higher load-bearing capacities and weaker strength loss upon deformation. The plastic zone extent depends on the system size in relation to the intrinsic material length scale, transitioning from strain localization to diffuse plastic zones as the model size reduces. These simulations have inspired novel rescaling coefficients, based on the shear band thickness to footing size ratio, which enables a more accurate rescaling of the ultimate bearing capacity of reduced-scale models to their prototype counterpart.