Hydraulic Gradient Based Low-Gravity Simulation System for Geomaterials

Low-gravity experimental simulation is essential for advancing extraterrestrial geotechnical research, yet existing techniques face limitations in cost, duration, and scalability. This study presents a novel ground-based low-gravity system founded on the Hydraulic Gradient Similitude Method (HGSM), which applies the upward seepage force to counteract gravity. A first-generation small-scale apparatus was developed by modifying a conventional triaxial system, integrating a precision-controlled water supply system, a kaolin-boundary-modified triaxial chamber, and a cone penetration test (CPT) module. Key innovations include: (1) stable low-gravity environments (>72 hours) with a gravity ratio (γ*) adjustable from 1/6 (lunar gravity) to 1 (terrestrial gravity); (2) compatibility with conventional granular materials (e.g., quartz sands and lunar regolith simulants); and (3) high measurement precision validated through calibration tests. Experimental results confirmed the capability of the system to simulate low-gravity CPT responses, indicating notable changes in shear resistance mechanisms under reduced gravity. Comparative analysis with existing experimental data and discrete element simulations of CPT under low-gravity further demonstrated the system's reliability. This work provides a cost-effective, long-duration platform for simulating quasi-static geotechnical processes in low-gravity environments, offering a promising solution for pre-mission equipment testing and data interpretation in extraterrestrial exploration.