Abstract: The 3D water-air two-phase seepage characteristics of undisturbed granite residual soil at REV (representative elementary volume) scale are examined by using the Level Set method based on computer tomography (CT) and AVIZO-COMSOL interactive docking technology. Results reveal that the residual air in pores mainly distributes in blocks on the pore edges, dead corners and abrupt changes of pore throats. A few main seepage channels, generally wide and straight, exist in the pores of the REV model. The two-phase seepage velocity is controlled by the tortuosity of the pores, yet with obvious advantage channels. The average flow velocity of the main seepage channel is 47.26% higher than the model as a whole. The maximum displacement resistance appears at the pore wall; the narrower the pore, the greater the resistance. The research finding offers an approach and a theoretical basis for further understanding the pore seepage law in undisturbed soil.

Key words: undisturbed soil, seepage characteristics, Level Set, representative elementary volume, CT scanning, two-phase flow