Abstract: Vacuum conditions (10-1 000 Pa) induce unique gas-liquid interface behavior and mass transfer processes in porous medium, significantly affecting multiple-phase fluid flow efficiency and the structural response of the medium. There is a complex relationship between multiphase flow in porous medium and geomechanical deformation processes; particularly in environments with active seismic faults, this relationship is a key factor, influencing the safety and stability of underground engineering projects such as geological carbon dioxide storage. This study proposesd a novel coupled model that incorporated gas slip effects, low-pressure adsorption-desorption kinetics, and dynamic contact angle equations to reveal the feedback mechanisms between gas-liquid interface evolution and multiple-phase fluid flow under vacuum suction. By quantifying the regulatory roles of equivalent osmotic pressure and low-pressure gradients on capillary force reconstruction and interfacial mass transfer, a dynamic evolution model of pores and fractures was established. This model enables high-precision simulation of low-pressure zone propagation, gas-phase channel formation, and matrix contraction during vacuum extraction. The results indicate that increasing the vacuum to 500 Pa increases the gas-liquid interface migration rate, widens the solid-liquid contact angle, and significantly optimizes the dewatering efficiency. At a higher vacuum degree (200 Pa), the interfacial migration rate accelerated further, and the dewatering efficiency approached a steady state within 10 minutes, far outperforming the results under lower vacuum conditions. This conclusion indicates that increasing the vacuum, by reducing residual pressure within the pores, restructuring capillary force equilibrium, and enhancing the interfacial advancement rate, can be a key factor in achieving efficient dewatering and low residual saturation, providing direct evidence for the parameter optimization of vacuum dewatering processes. This model provides theoretical support for vacuum dehydration technology, the design of porous filtration media, and surface treatment processes.

Key words: vacuum pumping, gas-liquid interface evolution, porous medium seepage, low-pressure coupling mechanism, numerical simulation