Stress- and strain-dependent dynamic properties of the EAC-1A lunar regolith simulant

The EAC-1A lunar mare simulant has been selected by the European Astronaut Center (EAC) for use in large quantities in the lunar simulation testbed of the LUNA analogue facility. The material is silty sand, as classified by sieving and laser diffraction analysis. Four batches of the material have been characterised in terms of particle size distribution and subsequently tested in a resonant-column device, employing several single-stage and multi-stage tests at different stress levels to determine the dynamic shear modulus and damping over a wide strain range. To facilitate application, equations have been derived for the stress dependence of the elastic shear modulus at small strains and the nonlinear response, characterised by a decrease in shear modulus and an increase in damping at larger strains. In terms of the shear wave velocity, the small-strain results can be used to infer the in-situ regolith state from seismic velocity records; findings for the nonlinear response are relevant to terramechanical applications.