Packing properties and steady strength of cemented loose granular materials

We study samples composed of loose cemented assemblies of particles under isotropic compression and biaxial shearing by means of a discrete-element approach. Compression tests are undertaken by consolidation of grains initially not presenting contacts under varying level of cementation and increasing confining pressure. We find a nonlinear evolution of the solid fraction with pressure that is described using the evolution of granular connectivity and the collapse of pores under homogeneous load. The poral space is characterized in terms of probability of void size number and volume distribution which, surprisingly, can contain voids as 30 times the size of an average particle. Under steady flow, the shear strength turned out to evolve non linearly with the cementation level. For cementation strengths below the confining pressure, the cementation between particles has little effect upon macroscopic friction angle. For greater values of cementation, a rapid increase of macroscopic friction occurs despite a drop in grain connectivity. Macroscopic cohesion is, in turn, small when compared with the interparticle bonding strength for highly cemented samples. The increment of macroscopic strength is found to deeply depend on the anisotropy of contact forces despite a homogeneous distribution of contact orientations and lower connectivity for highly cemented samples.

Automated summary

We used a discrete-element approach to study the behavior of loose cemented particle assemblies under isotropic compression and biaxial shearing. The results show that the solid fraction evolves nonlinearly with pressure, which is influenced by the evolution of granular connectivity and the collapse of pores. The poral space is characterized by the probability of void size number and volume distribution, and surprisingly, can contain voids as large as 30 times the average particle size. Under steady flow, the shear strength exhibits a nonlinear relationship with the level of cementation. For cementation strengths below the confining pressure, the cementation between particles has little effect on the macroscopic friction angle. However, for higher levels of cementation, there is a rapid increase in the macroscopic friction despite a decrease in grain connectivity. The macroscopic cohesion is small compared to the interparticle bonding strength in highly cemented samples. The increase in macroscopic strength depends on the anisotropy of contact forces, despite a homogeneous distribution of contact orientations and lower connectivity in highly cemented samples.