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Study on the improvement of grouting stone properties in coal mine goafs using combined denitrifying bacteria

He, Hao1; Xu, Nengxiong1; Qin, Yan1; Xu, Tianchi1; Guo, Yuxi1

Published Aug 30, 2024 on Dryad. https://doi.org/10.5061/dryad.0000000bq

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Aug 30, 2024 version files 24.63 KB

Abstract

Grouting can effectively reduce residual deformation of coal mine goafs, but fly ash grouting materials suffer from poor flowability and slow early strength development. Microbially Induced Calcite Precipitation(MICP), with its high environmental compatibility and minimal disturbance to geotechnical bodies, effectively improves the injectability of grouting slurry in goafs. This study combined Castellaniella denitrificans and Sporosarcina pasteurii to induce calcite precipitation, preparing cement-fly ash slurry with varying water-solid ratios, solid ratios, and denitrifying bacteria concentrations. The physical properties of the slurry and the mechanical properties of the grouted stone bodies under sealed curing conditions were measured. Results showed that the strength of the stone bodies cured by MICP increased rapidly within 7 days, and the strength reached the standard 2.03 MPa at 28 days under conditions of low solid ratio and high water-solid ratio. At a water-solid ratio of 1:1.2 and a solid ratio of 15%, initial and final setting times were 97.46 and 127.31 hours, respectively, indicating that MICP enhances slurry fluidity, providing more time for grouting construction in goafs. Dual-bacteria MICP improves stone body performance by enhancing cohesive, frictional, and interlocking forces, with the best compressive strength at a denitrifying bacteria concentration with an optical density of 0.8 at 600 nm wavelength.