Investigation of gravity effect on penetration resistance in Tongji-1 lunar regolith simulant by centrifuge tests

Cone Penetration Tests (CPTs) are usually performed on the lunar regolith simulant on the Earth to study the geotechnical characteristics of lunar soil, which will be then used for the possible human activities on the Moon in the future. However, the gravity effect should be fully investigated before applying these experimental results to the Moon exploration, because the gravity level on the Moon is much lower than that on the Earth. For this aim, a series of CPTs was carried out in a centrifuge with a carefully designed testbed made of Tongji-1 lunar regolith simulant (TJ-1 simulant). The measured results were employed to examine the applicability of two traditional solutions and linear equation in describing the gravity effect along with some other existing experimental data. In addition, the linear equation fitted by the experimental data was used to predict the values of normalized tip resistances of lunar soil on the Moon. The results show that the two traditional solutions cannot describe the gravity effect well while the linear relationship between the peak (stable) normalized cone tip resistance and the reciprocal of gravity level can quantitatively describe the gravity effect on the penetration resistance. The predicted normalized peak (stable) tip resistances are larger than those of lunar soil on the Moon, which may be probably due to the unique in-situ conditions on the Moon.