Simulation of Icy Lunar Regolith and Experiment on Its Shear Strength

Abstract

In order to obtain the shear strength of Icy Lunar Regolith (ILR) in the Permanently Shadowed Region (PSR) of the Moon, the physical properties of ILR such as mineral composition, particle size distribution, dry density, water content and deposition temperature were analyzed, and a method for ILR simulant preparing and parameters testing was proposed. Based on the Variable-Angle Shear Test (VAST) method, shear strength tests of ILR simulant were conducted with a mixed raw material made of anorthosite and basalt, dry density of 1.71g/cm³ (i.e. 100% relative density), water content from 3.7 wt% to 9.5 wt%, and temperature below –180°C. The result shows that the shear damage mode of the ILR simulant under low confining pressure is dominated by brittle fracture on the shear surface, but with the increase of the confining pressure, the brittleness of the ILR decreases and the ductility increases. In this case, its damage mode changes to compression-shear damage, and the shear strength decreases. The shear strength parameters of the ILR simulant under low confining pressure were calculated according to the linear Mohr-Coulomb criterion. The results show that the cohesion increases linearly with the increase of water content, but the internal friction angle hardly varies with water content, with values between 50° and 53°.

Keywords

Icy Lunar Regolith (ILR) / Lunar Regolith Simulant (LRS) / Variable-Angle Shear Test (VAST) / shear strength / Mohr-Coulomb theory