基于FBM的部分充填裂隙渗流特性仿真研究OA

[Background]Natural rock fractures are often partially filled with permeable materials such as silt and miner-als under long-term geological and hydraulic actions,forming complex structures containing unfilled voids.The seepage characteristics of such fractures significantly influence petroleum extraction,mine water prevention,and the stability of underground engineering projects.[Methods]To reveal the underlying seepage mechanisms,this study generated rough profiles of unfilled voids with different fractal dimensions based on Fractional Brownian Motion.A theoretical expres-sion for the overall permeability of partially filled fractures was derived,and a coupled free flow-porous medium flow numerical model was established.This framework was used to systematically investigate the effects of fracture pressure drop,residual aperture,and filling matrix permeability on the seepage behavior and overall permeability of partially filled fractures.[Results and Conclusions]The results indicate that:(1)The overall permeability of partially filled frac-tures remains stable under low pressure drops but decays under high pressure drops due to inertial effects;vortex in-duced by rough walls can reduce permeability by up to approximately 25.9％.(2)The residual aperture plays a dominant role in controlling fracture permeability and the effective hydraulic aperture,with its influence significantly stronger than that of the fractal dimension of roughness.As the residual aperture increases from 0.1 mm to 5 mm,the overall permeab-ility exhibits nonlinear growth,spanning six orders of magnitude(from 10-12 m2 to 10-6 m2).(3)The influence of filling matrix permeability can be divided into three stages:in the low-permeability stage(k＜10-10m2),flow is dominated by the unfilled void,and the overall permeability remains stable;in the intermediate stage(10-10＜k＜10-5m2),the overall per-meability increases with matrix permeability,and the flow distribution approaches the geometric proportion;in the high-permeability stage(k＞10-5m2),the permeability growth slows and gradually stabilizes,with the influence of matrix per-meability weakening as the residual aperture increases.(4)In the low filling matrix permeability stage(k＜10-10m2),the theoretical predictions of the overall permeability of partially filled fractures show good agreement with numerical simu-lations across varying fractal dimensions and residual apertures,demonstrating the model's effectiveness in representing the seepage behavior of such fractures.