Assessment of significant geotechnical parameters for lunar regolith excavations

Geotechnical properties of the lunar regolith show a significant dependency on the depth of the regolith and the geographical location. In-Situ Resource Utilization (ISRU) concept requires extensive excavations on the regolith at varying depths over a substantial area. However, these excavations would be severely affected by abrupt changes in resistive forces and traction losses due to increased shear strengths with depth. In addition, these could generate high amounts of dust, and the mechanical parts of the equipment could be damaged by abrasive particles. Therefore, this critical review aims to analyse novel excavation concepts and discuss their effectiveness in mitigating the potential issues pertaining to the lunar regolith. 5 main excavation force reduction methods are identified, namely, pre-treatment mechanisms, integrated mechanisms, advanced tool designs, continuous mechanisms, and pneumatic methods based on their mechanisms to reduce resistive forces in excavation. Additionally, the potential measures to overcome dust issues, wear and tear, and traction losses were presented in this work, alongside a summary of advances in lunar regolith drilling. No concept could be identified as a fully optimised solution to all the geotechnical considerations. The partially optimised designs could incur unpredicted monetary losses in the actual lunar regolith excavations. Therefore, 4 key geotechnical considerations for the lunar regolith excavations are presented and those could be used as a performance evaluation criterion. Optimising these criteria is of paramount importance before the actual lunar excavations.