A new smoothed particle hydrodynamics (SPH) solver is presented to simulate strongly-coupled hydro-mechanical processes (SC-HMP) in saturated geomaterials. SC-HMP take place when saturated geomaterials are subject to loading which are relevant to many practical problems including land subsidence in geomechanics, soil liquefaction in earthquake engineering, fluid injection/extraction in geophysics, wave-seabed interaction in ocean engineering, underground carbon dioxide storage in geoenvironmental engineering, etc. The ability to predict SC-HMP is crucial for the understanding of behaviours of saturated geomaterials and nowadays numerical modelling serves as a promising tool. This thesis explores the simulation of SC-HMP with the meshless SPH method, which is capable of handling large deformation and hence has the potential to outperform the widely used mesh-based solvers. New SPH formulations for the u-w-p and u-p versions of the Biot's model are proposed. A salient feature of such formulations is the need for explicit treatment of free-surface conditions. This provides an opportunity to explicitly enforce multiple types of boundary conditions which are challenging for a classical SPH formulation but are essential for problems involving SC-HMP. A new generalised technique for applying explicit boundary conditions is proposed, with significant innovation in 3-D including the introduction of Rodrigues' rotational formula to perform coordinate transformations. The application of several specific boundary treatments is then proposed. Moreover, two new stabilisation measures are proposed to counteract the numerical challenges of SPH for geomaterials. Specifically, multiple new hourglass control measures are formulated and evaluated in an updated-Lagrangian framework to address the zero-energy modes and the volumetric strain diffusion technique is proposed to alleviate the volumetric locking issue. These developments are implemented in the open-source SPH solver DualSPHysics to improve computational efficiency. The solver is validated first against poroelastic tests whereby the solid skeleton of geomaterials is assumed to be linear elastic. This includes quasi-static tests of 1-D consolidation and Mandel's problem, and dynamic tests of 1-D harmonic loading, 1-D transient wave propagation, 2-D consolidation and 2-D transient wave propagation. The volumetric locking issue is identified and the effectiveness of the proposed volumetric strain diffusion is demonstrated. The range of applicability of the u-w-p and u-p models is also examined. The new SPH u-w-p model is shown to produce superior behaviour for fast phenomena. In general, the SPH results match with the reference data and they also exhibit the desired rate of convergence. The solver is then validated against 3-D triaxial tests to examine the implementation of elastoplastic constitutive models, including Drucker-Prager, Mohr-Coulomb and modified Cam-clay models. A new SPH triaxial model is proposed based on the explicit boundary conditions. Drained monotonic tests are performed enabling the effectiveness of hourglass control measures and volumetric strain diffusion technique to be examined and demonstrated. The obtained stress-strain relations agree with the reference data. The validated solver is finally applied to a practical problem of consolidation and failure of silo foundations. Two scenarios of single silo and twin silos are simulated with results showing that the new SPH model can reproduce the failure mechanisms of silo foundations. The developments presented in this thesis provide a solid basis for further SPH modelling of SC-HMP involving more complex geomaterial behaviour.
- Smoothed particle hydrodynamics
- Biots theory
- Plasticity
Modelling of strongly-coupled hydro-mechanical processes (SC-HMP) in saturated geomaterials using smoothed particle hydrodynamics (SPH)
Yao, C. (Author). 31 Dec 2023
Student thesis: Phd