Experimental Study on the Width of the Reasonable Segment Pillar of the Extremely Soft Coal Seam in the Deep Mine

Various dynamic disasters will happen in the extremely soft coal seam mining process of Gob-side entry in the deep mine, including large deformation of roadways, rock burst, gas unusual, floor water invasion, spontaneous combustion of coal seam and so on. Therefore, a reasonable segment pillar will not only avoid the dynamic disasters in the excavating process, but also improve the resource utilization. Taking the goaf working face of extremely soft coal seam in the deep mine in one particular mine of Shandong Province as the engineering example, this paper first analyzes optional locations of the gob-side entry, finding that the gob-side entry should be located in the low stress block and it’s the most favorable to keep small pillars and goafs isolated. Then, it is found that small surrounding rock deformation of gob-side entry takes place in the driving process through the numerical simulation, and the deformation will increase with the increasing width of the chain pillar. The surrounding rock deformation of gob-side entry increases in the stoping stage. Small width of the chain pillar will easily result in the instability of the roadway. As the swivel angle of the basic roof increases, the surrounding rock deformation of gob-side entry will accordingly increase. Finally, the numerical calculation and on-spot mine pressure monitoring illustrate that the width of the segment pillar in the gob-side entry should be 5–7 m, with 6 m the best.