Tortuosity quantitatively reflects the complexity of porous media. For the diffusion process in porous media, diffusive tortuosity is inevitably an important research topic. A simulation experimental method is proposed to study diffusive tortuosity in granular soil based on 3D pore-scale simulation by smoothed particle hydrodynamics (SPH). On the basis of the simulation results, the relationships between diffusive tortuosity and microstructural parameters are discussed. Simulation experiments are implemented on 3D granular soil columns generated by PFC software and soil layers formed by periodic expansion of the soil columns. The accuracy of the pore-scale SPH diffusion model is verified by the analytic solution for the particular case of a pure water column. The results show that the dimensionality does affect the diffusive tortuosity. 2D profiles cannot represent the original 3D medium in terms of the diffusion characteristics. Within the limited range of the variation of porosity during soil compression, the relationship between porosity and diffusive tortuosity can be considered to be linear. In addition, for the case of uniform granule size, diffusive tortuosity is almost linearly related to the specific surface area. Tortuosity values for soil columns are larger than those for the soil layer, which denotes that the effect of the sidewall on diffusion cannot be overlooked for a centimeter-scale soil column.

中文翻译：

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基于颗粒土孔隙尺度SPH模拟的扩散曲折影响因素研究

曲折度定量地反映了多孔介质的复杂性。对于多孔介质中的扩散过程，扩散曲折不可避免地是一个重要的研究课题。基于光滑粒子流体动力学（SPH）的3D孔隙尺度模拟，提出了一种模拟实验方法来研究颗粒土中的扩散曲折。在模拟结果的基础上，讨论了扩散弯曲度与微观结构参数之间的关系。在PFC软件生成的3D颗粒土柱和土柱周期性膨胀形成的土层上进行模拟实验。孔隙尺度 SPH 扩散模型的准确性由纯水柱特定情况的解析解验证。结果表明，维数确实会影响扩散曲折度。就扩散特性而言，2D 剖面不能代表原始的 3D 介质。在土体压缩过程中孔隙度变化的有限范围内，孔隙度与扩散曲折度之间的关系可以认为是线性的。此外，对于均匀颗粒大小的情况，扩散曲折度几乎与比表面积呈线性相关。土柱的曲率值大于土层的曲率值，这表明对于厘米尺度的土柱，不能忽视侧壁对扩散的影响。对于均匀粒径的情况，扩散曲率几乎与比表面积呈线性相关。土柱的曲率值大于土层的曲率值，这表明对于厘米尺度的土柱，不能忽视侧壁对扩散的影响。对于均匀粒径的情况，扩散曲率几乎与比表面积呈线性相关。土柱的曲率值大于土层的曲率值，这表明对于厘米尺度的土柱，不能忽视侧壁对扩散的影响。