Effects of Ambient Moisture and Large‐Strain Dynamic Preloading on the Dynamic Properties of the EAC‐1A Regolith Simulant

The EAC‐1A lunar mare simulant, a silty sand, was selected by the European Astronaut Center (EAC) for use in the LUNA analogue facility's lunar simulation testbed. Its stress‐ and strain‐dependent shear modulus and damping ratio were determined via resonant column testing on specimens prepared either from ambient moisture material or oven‐dried material. Significant differences were observed across the strain range. The tests further examined specimen behaviour during unloading from large to small strains and subsequent reloading. The reloading curves were observed to merge with the virgin response curves at the strain corresponding to load reversal, while a notable degradation of the small‐strain modulus due to prior loading was evident. The overall behaviour in terms of shear modulus and damping was captured using simple equations.