Generalization of non-monotonic atmospheric-water effects across particle size distributions

Determine whether the non-monotonic effects of absorbed atmospheric water on shear strength and cohesion, observed in the Lunar Highlands Dust Simulant (LHS-1D), are consistent across granular regolith simulants with differing particle size distributions, and quantify how the magnitude of these effects varies with particle size distribution.

Background

The study constructed three-dimensional shear strength surfaces for the Lunar Highlands Dust Simulant (LHS-1D) with and without absorbed atmospheric water and found non-monotonic changes in shear strength and cohesion depending on bulk density and normal stress. For midrange densities, approximately 0.4 wt.% absorbed water increased cohesion by about 15%, while at higher normal stresses the water effect was smaller.

Because these tests were limited to LHS-1D, the authors highlight an unresolved question regarding whether the same non-monotonic pattern and its magnitude apply to other granular regolith simulants that have different particle size distributions. They suggest that water’s ability to permeate and affect interparticle forces may vary with particle size distribution, motivating investigation across diverse simulants and conditions (e.g., vacuum).