Pore connectivity of simulated vesicular mare basalt: Implications for the gas sealing performance of lunar lava tubes

Lunar lava tubes are promising sites for future lunar bases because they provide natural radiation shielding and relatively stable thermal conditions. However, it remains unclear whether their surrounding rocks and overburden can maintain an internally pressurized environment under lunar high vacuum. This study used vesicular basalt from Northeast China as an analogue for lunar mare basalt, evaluating its morphology, mineral composition, density, and porosity. High-resolution X-ray CT imaging and digital core reconstruction, combined with a maximal-ball algorithm, extracted a pore-throat network and quantified pore connectivity and gas permeability. The basalt is dominated by spherical and ellipsoidal pores, with approximately 19.4% porosity and 2.03–2.27 g/cm 3 density, closely resembling lunar mare basalt. Pore-network analysis showed approximately 62.4% connected pores, indicating high porosity but limited effective connectivity. A pore-scale steady-state gas-flow model based on the Hagen–Poiseuille equation and nodal mass conservation agreed well with permeability tests, supporting the network model's reliability. A three-dimensional equivalent permeability tensor revealed clear anisotropy and directional coupling. In site-scale gas-leakage simulations, gas transport concentrated near the cavity roof and low-resistance regions. Transient results showed rapid early gas loss after supply stopped, followed by slower pressure decline. Under the material properties, permeability tensor, cavity geometry, overburden thickness, and boundary pressure considered here, natural analogue wall rock and overlying regolith alone may be insufficient to maintain long-term pressure, suggesting that engineered sealing should be evaluated for comparable lunar lava-tube habitats. These permeability properties and the equivalent tensor are effective values from one representative terrestrial vesicular-basalt specimen, not universal properties of lunar mare basalt. Moreover, the continuum-flow model mainly applies to laboratory and relatively high-pressure conditions; rarefaction effects may become important near lunar vacuum.