Cone penetration resistance of CUMT-1 lunar regolith simulant under magnetic-similitude lunar gravity condition

The cone penetration test (CPT) has shown great potential in coming lunar in-situ resource utilization and base construction missions. To investigate the effect of lunar low gravity and special regolith characteristics, a series of miniature cone penetration tests were conducted under lunar gravity, after which the penetration responses and mechanism were analyzed. Properties of the lunar regolith were reproduced by the CUMT-1 simulant, which shows good consistency with the lunar regolith in mineralogy, particle morphology, grain gradation, and mechanical behaviour. Lunar gravity was simulated through the recently developed geotechnical magnetic-similitude-gravity model testing (GMMT) method. The results show that the increase in gravity leads to a nonlinear increase of the penetration resistance, which is more significant at low relative density and is weakened by increasing assemble density and particle irregularity. The evolution of cone index gradient and normalized penetration resistance at lunar gravity was further analyzed, which shows a good agreement with the in-situ results performed by Lunokhod and Apollo missions. Finally, a back prediction of internal friction angle suggests that the gravity-induced stress level promotes an increase in internal friction angle, but the gravity-induced stress gradient suppresses this trend.