Geomechanical Assessment of Chang’e-5 Lunar Regolith Using High-fidelity Simulant

Conducting experimental research using lunar regolith simulants on Earth is essential for understanding the geotechnical properties of lunar surface material and its interaction with equipment such as lunar rovers and landers, given the limited quantity of returned lunar samples. The particle size and morphology of regolith significantly influence their mechanical properties. We developed a high-fidelity lunar regolith simulant by pulverizing, desiccating, sieving, and blending natural terrestrial minerals or rocks, based on the key characteristics of the Chang’e-5 lunar samples. To evaluate the fidelity of this simulant, we used X-ray micro-computed tomography to scan both Chang’e-5 lunar regolith samples and the simulant. This technique generated high-resolution (~1 μm) grayscale images that recorded the three-dimensional geometric features of individual particles. A machine learning-based segmentation tool was used to extract the outlines of particles from a three-dimensional perspective, enabling the determination of particle morphology using the discrete Fourier transform (DFT) method. A comparative analysis of particle size and morphology was conducted, including shape indicator, roundness, and surface roughness. Results demonstrated that our simulant exhibits high geomechanical fidelity compared to the Chang’e-5 lunar regolith samples. Furthermore, the discrete element method (DEM) was applied to investigate the mechanical behaviors of the two granular materials, based on direct shear and triaxial tests. Our results indicate that the lunar regolith may have cohesion and friction angle of 0–13.5 kPa and 35.7–40.3°, respectively. Angular fine particles with a rough surface enhance the shear strength of lunar regolith. This finding underscores the potential of our simulant to facilitate experimental investigations into the technical challenges posed by lunar regolith to equipment.