A limit analysis of the kinematics of void collapse using the discrete element method

Abstract

Discrete element modelling of oedometer tests has been performed to investigate the kinematics of void collapse by measuring the void reduction as a result of completely removing particles in the oedometer one after another. For smooth conditions, it is found that volume change due to a ball being removed in an oedometer is approximately equal to the volume of the ball removed plus its associated void space. For frictional balls, this finding is only true once the formation of soil arching in the oedometer reaches a constant condition. Soil arching forms in samples with frictional particles and creates stable voids within the oedometer sample. The extent of soil arching generally increases with increasing coefficient of particle friction. However, it is found that, at high coefficients of particle friction, the correlation with the extent of soil arching is weak. It has been shown that if void reduction in an oedometer is to be evaluated accurately, at least 20 particles need to be deleted to obtain a good average of void reduction per particle deleted. It is also important to allow soil arching to reach a constant condition before extracting any void reduction data.

Keywords:

• numerical modelling
• statistical analysis
• compressibility
• friction

Acknowledgements

The authors would like to thank EPSRC for their financial support for this project.