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

QIU Hongjie; QIU Xianyang; ZHANG Shu; SHI Xiuzhi; TAO Ming; CAO Rihong; CAO Mingyu

doi:10.13225/j.cnki.jccs.2023.1635

Abstract：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 soft-ware 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 es-tablished 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 back-fill'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 res-ults 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 velo-cities;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.