Interface fraction strength of LHS-1 Lunar regolith simulant against typical materials

Understanding soil–structure interaction is critical for the design of future lunar infrastructure. This study investigates the interface shear behaviour of the high-fidelity lunar regolith simulant LHS-1 through a series of direct shear tests. The primary objective was to determine peak and residual interface friction angles (δₚ and δᵣₑₛ) under conditions representative of both lunar and terrestrial environments. Tests were conducted using five interfaces with varying roughness—smooth steel, aluminium alloy, carbon fibre, rough steel, and sandpaper—across a wide range of effective normal stresses (0.28–150 kPa) and shear rates (0.005–5 mm/min). Specimens were prepared at a controlled relative density (~85%) using dry pluviation, and cyclic shearing was applied up to 70 mm cumulative displacement.

Results demonstrate that interface roughness significantly influences shear strength, particularly at low normal stresses (<4 kPa), where increased roughness leads to higher residual friction angles. The simulant exhibits abrasive behaviour, progressively reducing interface roughness during shearing. Additionally, shear rate effects were found to be negligible under dry conditions but became significant in the presence of fluid, with slower rates resulting in higher residual strength. These findings provide valuable insight into regolith–structure interaction and highlight key parameters for the design and modelling of lunar surface systems.