A coupled CFD-DEM method with moving mesh for simulating undrained triaxial tests on granular soils
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ORIGINAL PAPER
A coupled CFD‑DEM method with moving mesh for simulating undrained triaxial tests on granular soils An Zhang1,2,3 · Mingjing Jiang1,2,3,4 · Colin Thornton5 Received: 8 June 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract A coupled computational fluid dynamics and distinct element method (CFD-DEM) is proposed to simulate undrained triaxial tests on granular soils. In this method, the compressible volume-averaged Navier–Stokes equations of continuity and momentum with an additional state equation are used for modelling liquid flows. In addition, the volume-averaged Navier–Stokes equations are modified by including the velocity of moving grid in their convective terms to settle the problem of variable boundaries in the process of undrained triaxial compression. Then the capability of the developed method is mainly examined by comparisons with the constant volume method of simulating undrained triaxial tests, which shows that the results of the CFD-DEM method can compare favourably with those obtained from the constant volume method. Finally, the influences of strain rate, initial pore pressure and fluid compressibility on the undrained behavior of granular soils are carefully studied. Keywords Undrained triaxial test · Distinct element method · Computational fluid dynamics · Moving grid · Fluid compressibility
1 Introduction Since undrained conditions are commonly encountered in a variety of situations, e.g. submarine landslides and earthquakes, the investigation of undrained behavior of granular soils has received significant attention in the geotechnical community in the last several decades. Extensive laboratory tests, especially undrained triaxial tests, have been performed to understand the mechanical properties of soil under undrained conditions. However, the detection of
* Mingjing Jiang [email protected] 1
State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
2
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China
3
Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
4
Department of Civil Engineering, Tianjin University, Tianjin 300072, China
5
School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
microstructures that govern the macro response of granular soils is usually ignored in laboratory tests. An alternative approach is to use the distinct element method (DEM), pioneered by Cundall and Strack [3], which has been proven to be a powerful tool to gain detailed micro information at the grain scale level in addition to the macroscopic response. To simulate undrained behavior of granular soils, various attempts have been made and can be classified into two categories [38]: constant volume method and coupled method. The constant volume method, assuming the particles and pore fluid to be incompressible, has been widely used by many researchers
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