Damage pattern of the cemented backfill at the jagged rock-fill interface under dynamic loading of blasting

The morphology of the rock-fill interface, formed during mining and filling operations in underground mines, is directly related to the destabilization and damage of the cemented backfill under dynamic blasting loads. Previous studies often simplify the rock-fill interface to a planar shape; however, exploration results of empty areas in the quarry often characterize the rock-fill interface with jagged undulations. Applying continuum mechanics and numerical simulation software based on the finite difference method, three models of cemented backfill with different morphologies of serrated rock-fill interfaces were established as the experimental group, and one model with a flat and straight rock-fill interface was established as the control group; The time-history curve of the explosive load on the walls of equivalent cavities after rock blasting was derived and incorporated into a numerical model to simulate the two-step perimeter hole blasting in quarries. The dynamic damage response of cemented backfill under blasting loads was investigated by combining it with the backfill's damage criteria, and the influences of factors such as sawtooth width (SW) at the rock-fill interface, cement-sand ratio (CSR), side hole distance (SHD), vertical stress (σh), and others on the damage extent and mode were determined. The results show that: The damage area of the cemented backfill at a planar rock-fill interface resembles a rectangle, whereas at a jagged rock-fill interface with larger sawtooth widths, the damage area tends to approximate a rhombus, making it more prone to wedge-shaped damage; When vertical stress (σh) is similar, between two adjacent cemented backfill layers with differing CSR, the layer with the higher CSR exhibits slower attenuation of the peak vibration velocity at each mass point, resulting in a larger damage area and an increased likelihood of interlayer misalignment due to inconsistent vibration velocities; With the CSR constant, a larger σh results in a smaller damage area; Furthermore, the damage area of the cemented backfill is inversely correlated with SHD, and in engineering practice, selecting a reasonable SHD is crucial to maintaining the stability of the cemented backfill when the quantity of explosives for side holes cannot be reduced.