Abstract
Accurately reproducing in situ stress and seepage fields is a core prerequisite for scaled physical modelling of deep underground engineering. This study develops a novel hypergravity-based scaled physical modelling system that integrates centrifugal acceleration with independent regulation of axial stress, confining stress and pore water pressure. Through the self-weight effect amplified under hypergravity, the system generates continuous stress gradients, while high-pressure intensifiers supply the axial and confining loads to reconstruct prototype in situ stress distributions. Two independent intensifiers separately control the inlet and outlet pore water pressures, thereby reproducing the subsurface seepage fields. Uniaxial compression experiments were performed on 3D-printed sandstone analogues using the proposed system. Under 100 g hypergravity, specimen failure initiates and concentrates at the bottom, reducing bearing capacity by 8.7%; under normal gravity, shear fractures develop around the internal cavern, indicating that normal-gravity scaled tests do not faithfully reproduce the rock damage evolution. Supplementary numerical simulations of overhang stability in salt cavern gas storage and bentonite buffer re-saturation in high-level radioactive waste repositories further support the effectiveness of hypergravity scaling: the hypergravity model reproduces the prototype stress distributions, plastic-zone morphology and water saturation evolution, whereas conventional 1 g models show substantial deviations. This modelling system provides an experimental framework to optimise the design and long-term safety assessment of deep underground infrastructures where coupled in situ stress-seepage behaviours dominate performance.