For tunnels built in the saturated silty sand ground, fine particles may be migrated into tunnels through seams of tunnel segmental joints and then seepage erosion is triggered, which may induce ground settlement. However, the process from fine particles erosion to the stress redistribution and soil properties’ change surrounding the tunnel and ground settlement has not been clarified up to now. For this purpose, five numerical tests of seepage erosion in granular soils around the tunnel are conducted using the Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) coupling method. The influences of buried depth and grain size distribution (GSD) of gap graded soils (mainly controlled by the fines content and mean particle size ratio from coarse to fine) on the seepage erosion around the tunnel are investigated. Eroded mass, fines loss mode, surface vertical displacement, stress redistribution, fabric anisotropy, soil behavior and water pressure around the tunnel during the seepage erosion process for five tests are presented and compared. The following results can be upscaled to the practical tunnel engineering, such as: (1) the number of fines loss, the eroded zone and the ground settlement increase with buried depth and mean particle size ratio; (2) the earth pressure near the crack significantly increases due to the stress redistribution induced by fines loss, and the stress redistributed area expands with buried depth; (3) the strength and stiffness of granular soils around the crack are significantly reduced by the seepage erosion. All results revealed that the CFD-DEM simulations provide a new sight on understanding the mechanics of tunnel seepage erosion from a microscopic perspective.

对于在饱和粉质砂土中建造的隧道，细小颗粒可能会通过隧道节理缝的缝隙迁移到隧道中，然后引发渗漏侵蚀，这可能会引起地面沉降。然而，到目前为止，从细颗粒侵蚀到应力再分布以及隧道和地面沉降周围土壤性质的变化的过程尚未阐明。为此，使用计算流体力学和离散元方法（CFD-DEM）耦合方法对隧道周围的粒状土壤中的渗流侵蚀进行了五个数值测试。研究了间隙梯度土的埋深和粒度分布（主要受细粉含量和平均粒径比由粗到细控制）对隧道周围渗流侵蚀的影响。腐蚀的质量 提出并比较了五个试验的渗流侵蚀过程中细粉的损失模式，表面垂直位移，应力再分布，织物各向异性，土的行为以及隧道周围的水压。以下结果可以推广到实际的隧道工程，例如：（1）细粉的数量，侵蚀区和地面沉降随埋深和平均粒径比的增加而增加；（2）由于细粒流失引起的应力再分布，裂纹附近的土压力显着增加，应力再分布面积随埋深的增加而增大。（3）裂缝周围的粒状土的强度和刚度因渗漏侵蚀而大大降低。