An Experimental Study on Triaxial Compression Tests and Cone Penetration Tests in Planetary Regolith Simulant under Low Gravity Fields

Lunar exploration projects aiming to develop space exploration of mineral resources outside of Earth have been relaunched recently by many countries together with commercial partnerships. The fundamental understanding of the mechanisms related to the low gravity fields and specific planetary regolith is therefore the key to further plans for site investigation, resource utilization, and outpost construction. The triaxial compression test is a conventional method for measurements of mechanical properties of various granular materials, whereas the cone penetration test (CPT) could serve as an effective in situ tool for site investigation in deep space exploration. In this article, the geotechnical magneto-gravity model testing method is adopted to conduct triaxial tests and CPTs in a type of magnetic regolith simulant, under various low gravity fields. Triaxial testing data indicate the influence of g-level on both stress-strain curves and shear strength characteristics, as well as the independence of critical-state indexes at failure. The interpretation of CPT data under low gravity fields is then investigated, showing that the correlations between soil properties and CPT measurements require modifications for the application of in situ tests in the near-earth space exploration. The findings of this study provide some insights into the mechanics under various gravity-induced stress gradients and potentially contribute to further developments on surface excavation, base construction, and resource exploitation.