Geopolymer-based modification of blasting sealing materials and optimization of blasting block size in coal seams of open pit mines

This research proposes the utilization of a geopolymer-based blasting sealing material to improve the profitability of coal sales and reduce the rate of coal fragmentation during blasting in open pit mines. The study first focused on optimizing the strength of the sealant material and reducing curing time. This was achieved by regulating the slag doping and sodium silicate solution modulus. The findings demonstrated that increasing slag content and improving the material resulted in an early rise in strength while increasing the modulus of the sodium silicate solution extended the curing time. The slag doping level was fixed at 80 g, and the sodium silicate solution modulus was set at 1.5. To achieve a strength of 3.12 MPa, the water/gel ratio was set at 0.5. The initial setting time was determined to be 33 min, meeting the required field test duration. Secondly, the strength requirements for field implementation were assessed by simulating the action time and force destruction process of the sealing material during blasting using ANSYS/LS-DYNA software. The rsults indicated that the modified material meets these requirements. Finally, the Shengli Open Pit Coal Mine served as the site for the field test. It was observed that the hole-sealing material's hydration reaction created a laminated and flocculated gel inside it. This enhanced the density of the modified material. Additionally, the pregelatinized starch, functioning as an organic binder, filled the gaps between the gels, enhancing the cohesion and bonding coefficient of the material. Upon analyzing the post-blasting shooting effect diagram using the Split-Desktop software, it was determined that the utilization of the modified blast hole plugging material resulted in a decrease in the rate of coal fragmentation from 33.2% to 21.1%. This reduction exhibited a minimal error of 1.63% when compared to the field measurement, thereby providing further confirmation of the exceptional plugging capabilities of the modified material. This study significantly contributes to establishing a solid theoretical basis for enhancing the blasting efficiency of open pit mines and, in turn, enhancing their economic advantages.(c) 2021 Published by Elsevier B.V. on behalf of China University of Mining & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).