Mechanism and application of energy release modification of coal pillar in high stress roadway in deep well

In view of the frequent occurrence of rockburst in the coal pillars of high-stress roadways in deep underground coal mines in China, the types and mechanisms of rockburst in coal pillars are studied by means of field investigation, theoretical analysis, numerical simulation and engineering test. A new method of preventing rockburst by releasing energy and modifying the coal pillars of high-stress roadways is put forward. Based on the method proposed, a series of research work such as the principle research, technical system design and underground industrial test are carried out. Based on the main force source types of coal pillar rockburst in roadways, combined with many typical cases of rockburst, the coal pillar rockburst in roadways in China is divided into three types: basic stress superposition type, additional stress induced type and self-creep instability type. The mechanical models and engineering criteria of the occurrence mechanism of coal pillar rockburst in roadways are established and deduced respectively, which reveals its occurrence mechanism. In this paper, a method of preventing rockburst by combining fracturing with grouting in high-stress roadway in deep mine is proposed. The principle of preventing rockburst is embodied in two aspects: “energy release” and “modification”. The underground industrial test shows that the crack initiation pressure of elastic core coal is about 40 MPa, and the overall maximum fracturing width is 19.5 m. The field monitoring proves that the method proposed can reduce the energy accumulation level of roadway coal pillar and increase the overall impact threshold of roadway coal pillar. A complete technical system of coal pillar energy release modification and erosion prevention in high stress roadways of deep underground coal mines is designed, including the “evaluation-inspection-check” method of impact risk of isolated coal body, the energy release technology of elastic nuclear hydraulic fracturing and the whole grouting reinforcement modification technology. The “vibration-stress-displacement” three-field monitoring equipment for the elastic nuclear fracturing of coal pillars in roadways and the PS-Z-A/B type inorganic two-component quick-setting integral grouting modified material have been developed.