Influence of friction on sampling disturbance of lunar surface in direct push sampling method based on DEM

The direct push sampling method is one of the most commonly used sampling methods in lunar regolith exploration. However, the disturbance of in situ bedding information during the sampling process has remained an unresolved problem. In this paper, the discrete element method is used to establish a numerical lunar soil simulant basing on the Hertz-Mindlin contact model. The result of simulated triaxial test shows that the macro mechanical parameters of the simulant accurately simulate most known lunar soil samples. The friction coefficient between the simulant and the wall of the sampling tube is also tested and used as the key variable in the following simulation and study. The disturbance phenomenon is evaluated by the displacement of marked layers, and a swirling structure is observed. The changing trend of the friction coefficient on the soil simulant void ratio and stress distribution is also determined.