The mitigation of surface subsidence in coal mines

Overlying-separation layer grouting technology refers to manufacturing grouting by mixing water, fly ash and other materials on ground in proportion, and then injecting into stratum of development zone on separation layer with high-pressure grouting pump to fill the separation layer space for mitigating surface subsidence in coal mine. In this study, the overlying-separation layer development and grouting subsidence mitigation mechanism were investigated by analyzing filling, supporting, cementation and expansion of grouting material. A calculation method for grouting subsidence mitigation was proposed based on the analysis of overlying rock and surface movement without grouting, deflection of grouting control layer and surface subsidence with grouting. The factors influencing grouting subsidence mitigation effects were analyzed to optimize overlying-separation layer grouting parameters. An evaluation method for grouting subsidence mitigation effects was proposed. The analysis results of examples indicated that subsidence coefficient of theoretical calculation is generally matched with that of numerical modeling, and the accurate evaluation of grouting subsidence mitigation effects by specific calculation can be simplified as measuring with the actual maximum surface subsidence values without and with applying grouting technology.