Development of Cement-Based Grouting Material for Reinforcing Narrow Coal Pillars and Engineering Applications

The problem needs to be solved about stability control of small coal pillars along goaf in the coal mining process. In this paper, the effects of water reducer, accelerator and expansion agent on the fluidity, setting time, expansion ratio and stone body strength of grouting materials were analyzed through orthogonal experiments, and the optimal ratio of grouting materials was obtained, and it is applied to the engineering site to obtain the reinforcement effect of the coal pillar grouting material on the coal pillar. The results of the study show that: When the dosage of the accelerating agent is 4%, the amount of water-reducer is 0.3%, and the amount of the expansive agent is 6%, the comprehensive performance of the grouting material is the best. After using the new coal pillar grouting material to strengthen the coal pillars, 30 days of monitoring were conducted to determine the deformation of the surrounding rock of the roadway. The shallow separation layer of the surrounding rock of the roadway was about 39.6 similar to 52.5 mm, and the accumulated separation layer of the deep rock was 28.5 similar to 29.5 mm, which were kept within the safe control range. The coal pillar grouting material can well fill the surrounding rock fissures and coupling and cement the broken rock mass, improve the bearing capacity of the narrow coal pillar, and enhance the overall stability of the surrounding rock of the roadway. The research results have important reference significance for similar coal pillar grouting.