Purpose

The purpose of this paper is to form a numerical simulation method for permeability coefficient that can consider the characteristics of gravel gradation and further explore the effects of indoor test factors and gradation characteristics on the permeability coefficient of gravel.

Design/methodology/approach

The random point method is used to establish the polyhedral gravel particle model, the discrete element method (DEM) is used to construct the gravel permeability test sample with gradation characteristics and the finite element method is used to calculate the permeability coefficient to form a DEM-computational fluid dynamics combined method to simulate the gravel seepage characteristics. Then, verified by the indoor test results. Based on this method, the influence of sample size, treatment method of oversize particles and the content of fine particles on the permeability coefficient of gravel is studied.

Findings

For the gravel containing large particles, the larger size permeameter should be used as far as possible. When the permeameter size is limited, the equal weight substitution method is recommended for the treatment method of oversized particles. Compared with the porosity, the pore connectivity has a higher correlation with the permeability coefficient of the sample.

Research limitations/implications

Insufficient consideration of the movement of gravel particles in the seepage process is also an issue for further study.

Originality/value

The simulation method described in this paper is helpful for qualitative analysis, quantitative expression of pore size and makes up for the defect that the seepage characteristics in pores cannot be observed in laboratory tests.

中文翻译：

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基于DEM和CFD方法的砾石渗透系数影响数值模拟

目的

本文旨在形成一种能够考虑砾石级配特性的渗透系数数值模拟方法，进一步探讨室内试验因素和级配特性对砾石渗透系数的影响。

设计/方法/方法

采用随机点法建立多面体砾石颗粒模型，采用离散元法(DEM)构建具有级配特征的砾石渗透率试验样品，采用有限元法计算渗透系数，形成DEM-计算流体动力学联合方法模拟砾石渗流特性。然后，通过室内测试结果进行验证。基于该方法，研究了样品尺寸、超大颗粒处理方法和细颗粒含量对砾石渗透系数的影响。

发现

对于含有大颗粒的砾石，应尽可能使用较大尺寸的渗透仪。当渗透仪尺寸有限时，超大颗粒的处理方法推荐采用等重置换法。与孔隙率相比，孔隙连通性与样品渗透系数的相关性更高。

研究限制/影响

对砾石颗粒在渗流过程中的运动考虑不足也是需要进一步研究的问题。

原创性/价值

本文所描述的模拟方法有助于孔隙尺寸的定性分析、定量表达，弥补了实验室测试无法观察到孔隙渗流特征的缺陷。