Numerical investigation on peak friction reduction due to gradation change in particle crushing

Abstract

Internal angle of friction which is also termed as friction angle of granular materials is a very important parameter since many of strength parameters such as shear strength and bearing capacity are depend on it. The friction angle varies with the confining pressure even without the consideration of particle crushing. High confining pressure leads to particle crushing and particle crushing alter the friction angle further by changing the particle number, particle size and shape of PSD curve. This study was carried out to identify the relation between the friction angle and gradation change occurs at particle crushing. Since it is difficult to perform such analysis with conventional laboratory equipments due to the difficulty of controlling the PSD, constitutive modelling was used. The numerical approach called Discrete Element Modelling (DEM) provided more advanced benefits such as ease of controlling and obtaining micro parameters such as coordination number and unbalanced force. Numerical samples were generated with different gradations and the same PSD with different particle numbers. All samples were subjected to conventional triaxial test with different confining pressures. The variation of peak friction angle was obtained and the results showed that this analysis can be used to predict the reduction of peak friction angle when crushing occurs at high confining pressures. The stress-strain and volumetric responses were obtained and compared with the experimental behaviours. They showed a good consistency with each other and confirmed the validity of the simulation.