Discrete element modelling of cavity expansion in granular materials
Geng, Yan (2010) Discrete element modelling of cavity expansion in granular materials. PhD thesis, University of Nottingham.
A granular material is usually an irregular packing of particles and its constitutive relationship is very complex. Previous researches have shown that the discrete element method is an effective tool for fundamental research of the behaviour of granular materials. In this research, discrete element modelling was used to obtain the macroscopic stress-strain behaviour of granular material in cavity expansion. The micro mechanical features and the mechanical behaviour of granular material at particle level have been investigated. A simple procedure was used to generate the samples with spherical particles and two-ball clumps. The influence of particle properties on the stress strain behaviour within an aggregate was investigated in biaxial test simulations. It was found that more angular clumps lead to sample more homogeneous and that the interlocking provided by the angular clumps induces a higher strength and dilation in the sample response. Interparticle friction was also found to have significant effect on the strength and dilation of the sample. The sample macromechanical properties can be obtained from these biaxial simulations. For investigating the effect of particle shape, the spherical or non-spherical(two-ball clump) particle shapes were used in the cavity expansion simulations. Monotonic loading was performed on a fan-shaped sample with various particle properties under a range of initial cavity pressures. The results were compared with calculated analytical solutions and existing experimental data in order to optimise the micro mechanical parameters governing the behaviour. The pressuremeter test data were adapted for this comparison since the theory of cavity expansion has been used to describe the pressuremeter tests in soil and rocks by many geotechnical researchers and engineers. This research showed that particle properties play an important role in soil
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