Research

This project focuses on the development and application of advanced numerical methods to investigate the formation and evolution of compaction bands in geomaterials. Specifically, hypoplastic constitutive modeling will be coupled with a phase-field approach to provide a robust and thermodynamically consistent framework for simulating strain localization phenomena. Compaction bands, which are localized zones of intense volumetric deformation, play a critical role in influencing the mechanical behavior and permeability of porous materials such as rocks and soils. Traditional numerical methods often struggle to capture their initiation and propagation due to mesh dependency and difficulties in tracking discontinuities. To address these challenges, the proposed study employs a phase-field formulation that regularizes discontinuities and enables the seamless simulation of evolving localization patterns.

Supershear earthquakes represent one of the most hazardous rupture modes because rupture velocities exceeding the shear-wave speed can strongly amplify ground motion through Mach-cone-like wave focusing. The uploaded paper develops a two-dimensional hybrid FEM/peridynamic framework to study the transition from sub-Rayleigh to supershear rupture in both dry and fluid-saturated media. In this framework, peridynamics is used to model solid deformation, damage, and rupture propagation, while FEM is used to solve pore-pressure diffusion and fluid flow in saturated porous media. The model is validated against Homalite impact experiments and PMMA frictional-interface experiments, and then applied to dry and saturated fault-like media. A key finding is that dry media may exhibit either direct supershear transition or the Burridge–Andrews mother–daughter crack mechanism, whereas fluid-saturated media favor direct supershear transition due to poroelastic effects near the rupture front. The study also shows that pore-pressure perturbations can accelerate rupture propagation and allow rupture speed to approach the fast compressional wave speed in saturated media. However, several important limitations remain. The current simulations treat rocks mainly as linear elastic materials and use a linear slip-weakening friction law. Natural fault zones, in contrast, involve plastic yielding, permanent damage, rate- and temperature-dependent friction, heterogeneous permeability, evolving pore pressure, and complex fault-zone geometry. These processes may strongly influence rupture acceleration, supershear transition, off-fault damage, and seismic energy radiation. The proposed project will therefore extend the existing FEM/PD framework toward a more realistic poro-elasto-plastic and thermo-hydro-mechanical model for dynamic earthquake rupture in mature fluid-saturated fault zones.

Granular materials exhibit regime transitions between solid-like, fluid-like, and gas-like behaviours, influenced by factors such as loading conditions, particle size distribution, density, and material strength. The transition between solid-like and fluid-like states is particularly significant, as it underpins critical phenomena like landslides, coastal erosion and sediment transport. It is also vital for optimising industrial processes and designing rovers for space exploration. Despite extensive research, the fundamental mechanisms governing these transitions remain poorly understood. This knowledge gap limits our ability to reliably predict geological events and optimise engineering and manufacturing processes. This project aims to advance our understanding of regime transitions in granular materials using novel laboratory micromechanical tests, coupled modelling of solid-fluid interaction, constitutive modelling and large-deformation analysis. Our consortium brings together expertise across diverse disciplines, including advanced experimental testing, numerical and physical modelling, geological engineering, robotics, and software development. All participating organisations will contribute to the research activities by leading research work packages, staff secondment and/or providing technical/infrastructure support. Alongside research, the project will facilitate staff exchange through secondments and networking and train young researchers in research and soft skills by training schools. These activities will help form lasting collaborations globally and train the next generation of researchers and engineers driving technological advancements in academia and industry. The project will also encourage knowledge exchange between universities and industry, enabling the real-world application of new knowledge in software and test equipment development, and the creation of new spin-out companies offering services in advanced experiments and numerical modelling.