Coal Wall Spalling Mechanism and Grouting Reinforcement Technology of Large Mining Height Working Face

To control the problem of coal wall spalling in large mining height working faces subject to mining, considering the Duanwang Mine 150505 fully mechanized working face, the mechanism of coal wall spalling in working faces was investigated by theoretical analysis, numerical simulation and field experiment. Based on analysis of coal wall spalling in the working face, a new grouting material was developed. The stress and plastic zone changes affecting the coal wall, before and after grouting in the working face, were analyzed using numerical simulation and surrounding rock grouting reinforcement technology was proposed for application around the new grouting material. The results showed that: (1) serious spalling of the 150505 working face was caused by the large mining height, fault influence and low roof strength, and (2) the new nano-composite low temperature polymer materials used have characteristics of rapid reaction, low polymerization temperature, adjustable setting time, high strength and environmental protection. Based on analysis of the working face coal wall spalling problem, grouting reinforcement technology based on new materials was proposed. Industrial tests were carried out on the working face. Field monitoring showed that the stability of the working face coal wall was significantly enhanced and that rib spalling was significantly improved after comprehensive anti-rib-spalling grouting measures were adopted. These results provide a basis for rib spalling control of working faces under similar conditions.

Investigation of the evolution and control of fractures in surrounding rock under different pressure relief and support measures in mine roadways prone to rockburst events

This paper studies the evolution and control of surrounding rock under different pressure relief support conditions in mine roadways in which rockburst events have occurred. The evolution of fractures in the surrounding rock was determined from borehole images obtained with a digital panoramic borehole camera, and the surface displacement due to the rockburst events in the mine roadway was measured. According to the existing problems of the original support system of the roadway, a new coupled support system to prevent rockburst events in mine roadways was proposed, resolving both the pressure relief and support of the roadway. Field measurements indicate that the effect on the roadway under the coupled method of pressure relief and support was more satisfactory than that under the original support system. With the coupled support method, the surface displacement of the roadway was approximately 0.6 m, fractures were distributed only in the soft structures and bolt anchorage areas, and the maximum depth of the fractures was 2.95 m. By contrast, under the original support system, fractures were distributed throughout the roadway surrounding rock, and the maximum depth of fractures was 6.75 m. This coupled roadway support technology of pressure relief and support effectively maintains the stability of the rock surrounding the roadway and ensures the safety of the working face. The research results can provide a reference for damage prevention and support of mine roadways prone to rockburst events.