Abstract
Soil dynamic analysis is of important significance to both geotechnical and earthquake engineering. The traditional numerical techniques based on meshes such as the finite element method (FEM), assume soil as a continuum. However, soil is a complicated material consisting of three phases and therefore exhibits some discontinuous behaviours. Traditional grid-based methods have limitations in dealing with these discontinuous phenomena due to the use of meshes. Instead, meshfree particle method can treat soil as an assembly of discrete particles and in essence, avoid the limitations, which shows its great potential in soil dynamics.The discrete element method (DEM) and smoothed particle hydrodynamics (SPH) were adopted as two major methods for this research. The primary objective of this research is to analyse the dynamic behaviour of cohesionless sand by the DEM independently and also saturated sand by the coupling the DEM and SPH. Consequently, four programs have been developed and also verified and validated against either theoretical solutions or experimental data, which are listed in the following order: (a) a two-dimensional DEM program for granular materials; (b) a three-dimensional DEM program for cohesionless sand; (c) a three-dimensional SPH program for water; (d) a three-dimensional coupled SPH-DEM program for saturated sand.
With these programs, either the static or the dynamic behaviours of cohesionless sand were studied. Particularly, the rotating drum test was repeatedly simulated in this research. Relevant main outcomes can be summarised: (a) The drum rotational speed has effects on multiple aspects including the bed motion mode, the dynamic angle of repose as well as the active region. (b) The values of the angle of repose of the static and dynamic states were not equivalent. (c) The 3D DEM model can give more realistic results than the 2D version considering either the particles motion or the repose angle. (d) The dynamic angle of repose of water was confirmed to be zero with an SPH rotating drum simulation. (e) The underwater repose angle was smaller than the natural repose angle of dry sand. (f) The employment of the mirror boundary condition can be a replacement of physical boundaries as a source of friction from the boundaries. (g) Multi-threading combined with the spatial decomposition method can improve the computational efficiency of DEM and SPH codes at a low cost.
| Date of Award | 24 Jun 2020 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Loizos Pelecanos (Supervisor), Kevin Briggs (Supervisor) & Christopher Williams (Supervisor) |
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