Exploring the micromechanics of non-active clays by way of virtual DEM experiments

The micromechanical behaviour of clays cannot be investigated experimentally in a direct fashion due to the small size of clay particles. An insight into clay mechanical behaviour at the particle scale can be gained by way of virtual experiments based on the discrete-element method (DEM). So far, most DEM models for clays have been designed on the basis of theoretical formulations of inter-particle interactions, with limited experimental evidence of their actual control over the clay's macroscopic response. This paper presents a simplified two-dimensional DEM framework where contact laws were inferred from indirect experimental evidence at the microscale provided by Pedrotti and Tarantino in 2017 (particle-to-particle interactions were probed experimentally by varying the pore-fluid chemistry, and the resulting effect was explored by way of scanning electron microscopy and mercury intrusion porosimetry). The proposed contact laws were successfully tested against their ability to reproduce qualitatively the compression behaviour of clay with pore fluids of varying pH and dielectric permittivity. The DEM framework presented in this work was intentionally kept simple in order to demonstrate the robustness of the micromechanical concept underlying the proposed contact laws. It is anticipated that a satisfactory quantitative prediction would be achieved by moving to a three-dimensional formulation, by considering polydisperse specimens and by refining the contact laws.