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 simply 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 h) 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.