Development and testing of self-swelling cartridge for use as stemming material in open-pit blasting -A quarry case study

This paper examines the problems of low explosive energy utilization rate and poor blasting efficiency due to the use of unsuitable stemming materials in open-pit blasting. A self-swelling cartridge stemming plug is developed for use in quarry and open pit blast hole stemming. The self-swelling cartridge stemming development and testing procedures are presented in the paper. Various amounts of magnesium-aluminum mix activator are added to a self-swelling agent to determine the optimum amount of activator that results in the quick initiation of hydration reaction of the self-swelling agent to achieve complete reaction within acceptable field production stemming time. The laboratory test results show that the reaction time of the self-swelling cartridge increases with activator content. The expansion pressure of the self-swelling cartridge and the shear force at its interface with the blasthole wall for different diameters of cartridges increase with the increase of the cartridge diameter. Thus, from the indoor test results, the self-swelling cartridge in a saturated state effectively sealed the simulated blast hole within about 1 h, with an expansion pressure of 26.3-49.8 MPa and a shear force of 113.4 kN. Field tests were conducted to compare the effects of the self-swelling cartridge and drill cuttings as stemming materials in a limestone quarry using high-speed photography and fragmentation analysis. The results show that the selfswelling cartridge stemming can effectively prevent blast hole blowout compared to the drill cuttings stemming. This is shown in the field fragmentation analysis comparing from zones using the self-swelling cartridge to the drill cutting stemming zone fragmentation. It is concluded that use of self-swelling cartridge stemming results in better blast fragmentation at lower cost and higher safety than drill cuttings stemming in open pit blasting.