Macroscopic and microcosmic consolidation law of loose coal grouting based on the “two media-three interfaces” model

In order to predict the effect of cement slurry grouting on reinforcing loose coal seam at Huaibei mining area in China,and provide some reasonable grouting parameters to ensure the stability of loose broken surrounding rock mass,this study revealed the grouting reinforcement law of cement slurry from macro-micro perspective. Based on the discrete element theory,the uniaxial compression test on the samples of coal-cement and the particle flow simulation software,the “two media-three interfaces” cementing model for loose coal and cement was developed. The model not only includes coal particles,cement particles,but also includes interfaces between particles. In the study,the coal-ce- ment consolidation microscopic mechanical parameters,the effects of ratio and porosity of the consolidation body were analyzed. The study shows that the “two media-three interfaces” model can not only simulate the rock mechanics experiment,but also model the influence of consolidation parameters,and is suitable for predicting the effect of grouting reinforcement. The uniaxial compressive strength (σc ) and the elastic modulus (E) of the consolidated body increase first,and then decrease with the increasing proportion of loose coal and cement particles. The process of increasing loose coal content is divided into two stages: the initial stage of aggregate reinforcement and the later stage of cementa- tion weakening. The uniaxial compressive strength ( σc ) and the elastic modulus ( E) of the consolidation body de- crease with increasing porosity,and the smaller particle and the higher degree of filling,the better the reinforcement effect. In the process of site grouting design and construction,using cement slurry with small particle size and good in- jection ability can obtain a better grouting reinforcement effect.