Seepage erosion around the underground pipelines will produce various adverse influences on the stratum stability and the structural safety. It involves behaviours at three scales, that is, particle-scale, cell-scale and engineering-scale. The problem relies on the fact that finding general equations for the granular media is difficult due to the changing nature of how solids flow, so that the continuous approach is unavailable to directly describe the phenomenon. Hence, DEM simulations are firstly conducted in this study to quantify the relationship between the fine particle loss (ΔFC = 0, 5%, 10%, 15%, 20%, 25%, 30%) and the mechanical properties of soil elements, upscaling particle to cell. Considering two initial fine grain contents (S6:4, S3:7), the empirical equations of soil mechanical parameters ε_ve, E₀, φ and c changing with the fine particle loss ΔFC are obtained by regression analysis. Then, based on the corresponding constitutive parameters of different erosional stages, FEM simulations at the engineering scale are conducted to analyse the structural mechanical response to the seepage erosion, upscaling cell to engineering. This study reveals the multiscale response of the seepage erosion in the sandy strata, and helps in providing the practical guidance for engineering application and the reference for the next multiscale parallel computation on this issue.

地下管线周围的渗流侵蚀会对地层稳定性和结构安全产生各种不利影响。它涉及三个尺度的行为，即粒子尺度、细胞尺度和工程尺度。该问题依赖于这样一个事实，即由于固体流动方式的变化性质，很难找到颗粒介质的一般方程，因此无法使用连续方法直接描述该现象。因此，本研究首先进行 DEM 模拟，以量化细颗粒损失（ΔFC =  0、5%、10%、15%、20%、25%、30%）与土壤元素力学性质之间的关系。 ，将粒子放大到单元格。考虑两个初始细粒含量（S6：4，S3：7），土壤力学参数的经验方程通过回归分析得到ε _ve、E ₀、φ和c随细颗粒损失ΔFC的变化。然后，基于不同侵蚀阶段对应的本构参数，在工程尺度上进行有限元模拟，分析结构对渗流侵蚀的力学响应，将单元升级为工程。本研究揭示了砂质地层渗流侵蚀的多尺度响应，有助于为工程应用提供实践指导，为下一步多尺度并行计算提供参考。