Experimental study on diffusion law of fly ash fluidized slurry filled in caving zone

LI Zhihua; GENG Qian; ZOU Enlong; MA Guojun

doi:10.11799/ce202502020

Abstract：To explore the groutability and grouting amount of filling in the caving zone of fly ash slurry,the experimental scheme was designed based on Talbol grading theory,and the porosity measurement and grouting diffusion test of single particle size and Talbol graded gangue granular materials were carried out.The results show that:①Under different mixing ratios,the theoretical porosity of gangue was generally consistent with the measured effective porosity.Additionally,the porosity exhibited a positive correlation with particle size.②When comparing the diffusion patterns of different slurry concentrations in gangue with varying gradations,it was found that for single-sized gangue injected with 60％and 65％concentration slurries,the diffusion followed a vertical-then-horizontal path.However,when single-sized gangue was injected with 70％concentration slurry or Talbol-graded gangue was injected with slurries of different concentrations,the diffusion process exhibited a horizontal-then-vertical pattern.③In the grouting tests,when a 60％concentration fly ash slurry was used,all nine experimental schemes successfully filled the target area.At a 65％concentration,only the single-sized 5～10 mm gradation showed"infiltration effects,"leading to ineffective injection.Under 70％concentration grouting conditions,single-sized 5～10 mm,15～20 mm,and Talbol-graded gangue all exhibited"infiltration effects."Based on these results,the optimal grouting concentration for fly ash was determined to be 65％.④Regarding the influence of different gangue gradations on grouting volume,it was found that for single-sized gradations,gangue particle size was positively correlated with both fly ash slurry injection volume and ash consumption.In Talbol gradation,when the gradation coefficient was 0.5,the gangue structure was the most compact,resulting in the least grouting volume.These findings provide an important theoretical reference for the utilization of coal-based solid waste in slurry backfilling within collapsed zones.