| The degree of hard roof, supporting manner and strength, overburden movement law and other factors affecting the stope tip curved triangle roof overhang distance, too large overhang distance will lead to gas gauge in the region, while causing other problems, especially in high-gas coal mine, curved triangle roof overhang problem has become a difficult problem to solve.This paper discussed two main ways to handle roof overhang problem: pre-split blasting and hydraulic fracturing, and compared the advantages and disadvantages, and applicable conditions of these two methods; combined the third mine of Yangquan Coal mine curved ends triangle top roof overhang situation, concluded that pre-split blasting and hydraulic fracturing treatment were not suitable for high-gas coal mine roof overhang. This paper introduced the "static broken technique "to handle overhang in high-gas coal mine, to achieve the curved triangle roof safe, efficient and environmentally friendly process of breaking rock.With the theoretical analysis+experimental+industrial test to analyze formation conditions in roadway ends curved triangle and its impact on the surrounding pillars, and calculated the maximum distance in curved triangle, with drilling on the K8113face peep, grasped the movement of the working surface overburden; studied the mechanism of static crushing rock breaking technology, gained the static crushing agents’ physical and chemical parameters, including:density, bulk density, expansive pressure, and water determination of mixed density, reaction heat release, as well as expansion of the relationship between pressure and pore size, the best water-cement ratio and other important parameters; in lab generated the form of static crushing agents crack in rock; using acoustic emission positioning technology to monitor the whole process of crack propagation, got some important results, such as" crack start from the lower part of hole","first cracking occurs first, after cracking occurs after behind","crack growth rate slow down after","vertical crack bedding direction parallel to bedding to expand faster than the speed of the direction of crack development"; based on the theory of elasticity and crack mechanics, analysis the process, expansion and crack arrest of crushing rock, established the static broken crack growth model, and found the relationship between crack length and crack propagation radius; to found further define the mechanism of action and appropriate drilling layout parameters with software ANSYS4.0, obtained that drilling should be less than ideal inter-row spacing0.8m; designed a reasonable drilling parameters and implied the industrial test in K8113, results showed static broken technique suited for artificial caving.After the anchors and nets were cut to meet the requirements in K8113working face, the distance of overhang length was generally more than20m in normal. In this research, a few hours after the industrial test, when the head forward3.2m, the downhill roadway roof coal caving gradually, limestone roof gradually began to collapse; further advance about9.6m, the test area has been completely collapse off. Compared before and after the industrial test, the distance of overhang length reduced7.2m.The research implemented to avoid the high-gas coal mine roadway ends hanging roof and other security problems, while reducing the bearing pressure and cut a conspicuous place on both sides of the goof pillar, verified static crushing technology for high-gas coal mine labor force roof conclusions. This research has important positive promotional value in Yangquan Coal Group and other coal mines, while dealing with similar issues for other mining provides a practical reference that makes sense. |
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