Research on hydraulic fracturing treatment technology for large-area suspended roof of reused roadway in working face with gob-side entry retaining
The hard and dense rock strata on the reused roadway of the 52306 working face with gob-side entry retaining in Yujialiang Coal Mine was difficult to collapse naturally and prone to hanging roof disasters,on the basis,the reasons for the formation of hanging roof on the reused roadway was analyzed,a hydraulic fracturing numerical simulation model for the hanging roof area of the reused roadway was established,the stress evolution law of the concrete wall on the side of the reused roadway was studied,and the pressure distribution characteristics of the hydraulic support,the deformation of the roadway surrounding rock,the ultrasonic monitoring data and their observation results of drilling holes before and after hydraulic fracturing were compared and analyzed.The research results showed that the main controlling factor of hanging roof disasters on hard roof was the span length of the hanging roof;the hydraulic fracturing technology for hard roof could effectively reduce the stress concentration of the concrete wall on the side of the reused roadway,reduce the deformation of the surrounding rock of the reused roadway,and a reasonable cutting range of 2-5 m for the hanging length of the upper part of the concrete wall was determined;after adopting hydraulic fracturing measures on the roof of the reused roadway,the overall average working resistance of the hydraulic support decreased by about 12％,and the deformation of the roadway was significantly reduced;the drilling observation results showed that the internal cracks of the borehole have significantly expanded,and the fracturing effect was significant;by adopting hydraulic fracturing measures on the roof,the cohesion between various rock layers was weakened,the hard roof was weakened,the tensile strength of the overlying rock layers was reduced,and the span length of the suspended roof was shortened and the degree of rock pressure manifestation was reduced.The roof of the reused roadway of the 52306 working face with gob-side entry retaining in Yujialiang Coal Mine had achieved significant subsidence,fracture,and collapse from the original long-distance hanging state,ensuring safe and efficient production of the mine.
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