A Constitutive Model for Lunar Soil

In light of the environmental differences (such as: gravitational fields, surface temperatures, atmospheric pressures, etc.), the mechanical behavior of the subsurface soil on Moon is expected to be different from that on Earth. This paper investigates the possible effect of surface energy forces on the shear strength of lunar soil. A method of modeling granular material by considering interactions at particle level has been developed which can accurately reproduce the overall mechanical behavior of soils under terrestrial conditions. The model is extended here to include surface energy forces between particles in order to describe the possible behavior of lunar soil under extremely low atmospheric pressure conditions. Given these conditions, the model shows an increase of the shear strength of the soil due to the effect of surface-energy forces. The magnitude of increased shear strength is in reasonable agreement with the observations of lunar soil made on the Moon's surface.