Quantifying Shear-Induced Permeability Changes in Medium-Loose Sands
Quantifying Shear-Induced Permeability Changes in Medium-Loose Sands
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DOI：
10.1061/jggefk.gteng-11874
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发表时间：
2024-02
影响因子：
3.9
通讯作者：
Jose Salomon;T. Morimoto;F. Patino-Ramirez;Catherine O’Sullivan
中科院分区：
文献类型：
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作者：
Jose Salomon;T. Morimoto;F. Patino-Ramirez;Catherine O’Sullivan
在岩土工程的许多应用中，准确评估土壤的水导率对于预测沉降和孔隙水压力变化非常重要。实验室测试数据可以为有限元分析中采用的渗透率参数提供信息；然而，在变形过程中渗透率的各向异性和演化不容易测量。研究了剪切作用对中松散液化砂渗透率及其各向异性的影响。采用离散元法（DEM）模拟了球形颗粒的单调不排水和排水三轴试验。利用计算流体力学（CFD）的有限体积（FV）模拟和孔隙网络模型（PNM）模拟对不同应变水平下三个正交方向的渗透率进行了评估。结果表明：在排水和不排水三轴条件下，剪切变形引起渗透率各向异性，且各向异性随轴向应变增大而增大。具体而言，结果表明，渗透率在主应力方向上增加，而在正交平面上观察到渗透率降低。不排水的变化纯粹是由织物驱动的，而排水的变化则受到体积应变的强烈影响。在这两种情况下，观察到在孔隙和连接相邻孔隙的收缩或喉道中存在一致的扭曲。这种小幅度的变化表明，对许多人来说，考虑剪切变形过程中渗透率各向异性演变的耦合有限元分析可能没有必要。然而，高分辨率FV模拟与计算效率高的PNM模拟相结合，可以分析颗粒材料中流动的驱动机制，并验证PNM在中等松散组件中的适用性。恒体积假设准确地反映了液化开始时接触的突然丧失，但不能再现在离心机和现场试验中观察到的渗透率变化。结果表明，如果考虑挠度和孔隙形状因子的变化，Kozeny-Carman （KC）框架可以用来描述各向同性和剪切渗透率的变化。
For many applications in geotechnical engineering, an accurate assessment of soil hydraulic conductivity is important to predict settlements and pore water pressure changes. Laboratory test data can inform the permeability parameters adopted in finite-element analyses; however, the anisotropy and evolution of permeability during deformation cannot be easily measured. In this study, the influence of shearing on permeability and its anisotropy in medium-loose liquefiable sands is investigated. The discrete-element method (DEM) is used to simulate monotonic undrained and drained triaxial tests using spherical particles. Finite-volume (FV) simulations using computational fluid dynamics (CFD), and pore network model (PNM) simulations are undertaken to evaluate permeability in three orthogonal directions at different strain levels. The results indicate that shear deformation induces anisotropy in permeability, in both drained and undrained triaxial conditions, and this anisotropy increases with axial strain. Specifically, the results show an increase in permeability in the direction of the major principal stress, whereas a reduction in permeability is observed in the orthogonal plane. Undrained variations are purely driven by fabric, whereas drained changes are strongly influenced by volumetric strain. In both cases, a consistent distortion in both the pores and the constrictions or throats connecting adjacent pores is observed. The small magnitude of the changes suggests that for many, coupled finite-element analyses accounting for the evolution of permeability anisotropy during shear deformation may not be necessary. However, the combination of high-resolution FV simulations with computationally efficient PNM simulations allow to analyze the driving mechanisms of flow in granular materials and to verify the applicability of PNM in medium-loose assemblies. The assumption of constant volume accurately captures the sudden loss of contacts at the onset of liquefaction, but cannot reproduce the permeability changes observed in centrifuges and field tests. Results indicate that the Kozeny–Carman (KC) framework can be used to describe isotropic and shearing permeability changes, if variations in tortuosity and pore shape factor are accounted.