Review of the mechanical properties of lunar soils

Abstract

This thesis summarizes the history of lunar soil exploration through the Surveyor and Apollo programs, 1966 - 1972. Our current knowledge of the physical and engineering properties of the lunar regolith is derived mainly from measurements made on bulk and core samples returned to earth, as well as trenching, penetration and simple geophysical experiments performed during the five successful Apollo missions to the moon. Most of this data corresponds to material in the upper 1 to 3 m of the lunar surface. Lunar regolith is comprised of a mixture of basalt, impact melt glasses, breccias and agglutinate particles, and is derived from processes related to surface impacts and volcanic activity. The soil itself has a particle size distribution that resembles a well graded silty sand with angular particles and often containing a significant fraction of crushable (hollow) glass spheroids and agglutinates. The soil typically has a specific gravity of 3.1 and is found at an average porosity of approximately 45 - 50 %. The material has both cohesive and frictional components of shear strength, the former presumed to be related to electro-static forces between particles. Recent Space Exploration Initiatives have motivated the development of simulants that replicate quite closely the average properties of lunar regolith. These materials provide the basis for future lunar and Martian exploration and construction priorities.