A Semi-empirical Analysis on Bearing Capacity Ability of Lunar Regolith

Abstract The bearing capacity of the lunar regolith, in particular the so-called stress-sinkage relationship, is crucial for designing large lunar vehicles. In this work, the bearing capacity of the lunar regolith is analyzed using a semi-empirical model on the packing of solid grains. The model suggests that lunar regolith with coarser solid grains shows better bearing capacity. By comparing with the stress-sinkage data of lunar boulder tracks, the regolith grains are likely to be crushed into smaller grains with a radius of ∼3.1–11.3 μ m when the normal stress on the lunar surface increases from zero to ∼50 kPa. Such a result suggests that the bearing capacity of lunar regolith can be affected by the fragmentation of regolith grains. The stress-sinkage data of lunar boulder tracks suggest a sinkage >0.5 m for a normal stress >25 kPa on the lunar surface. If the wheels of large lunar vehicles still follow the standards of terrestrial wheels, i.e., 14–21 inches or ∼0.36–0.53 m, we cannot avoid the wheels becoming stuck given the potential normal stress of at least tens of kPa for the wheel-ground interactions. Based on the results in this work, the bearing capacity of the lunar regolith can be improved by suppressing the fragmentation of regolith grains, which would be achieved by mixing the lunar regolith with the coarser grains consisting of other more ductile materials.