Abstract: Compressive bearing and force transmission characteristics of granular backfill are of great significance to control the surface deformation in backfill mining. The compression tests were conducted on five types of granular materials including pebbles, gravel, mine tailings, river sand and tailings, and seven gradations pebbles under lateral confinement. The compaction process and the influence of particle size on deformation and bearing capacity were analyzed. Meanwhile, based on the numerical simulation test of the pebbles, the force transmission characteristics were revealed. The results indicate that the bearing process of granular backfill under lateral confinement can be divided into three stages, i.e. void compaction, particle crushing compaction and granular compaction consolidation. The type of granular material and particle size have no effect on its nonlinear compaction process, but have a remarkable effect on the process of internal structure reorganization. In the process of compression, there is a critical compactness that reverses the order of bearing capacity of pebbles with different gradations, and the average deformation modulus of pebbles and the characteristic factor of particle have a negative exponential relationship. Numerical simulation test of pebbles reveals the strength distribution of the force chain and the “pressure arch” inside granular materials. It confirms the facts that the vertical stress in granular backfill decreases along the loading direction, and lateral pressure first increases and then decreases throughout the filling height.

Key words: granular backfill, confined compression, bearing characteristics, deformation modulus, force transmission