Analysis on Roof Falling Hidden Danger Grading of Mining Gateway

Abstract：According to the problem too hard on time to find and identify the high roof falling risk area in the mining gateway,a stable span identification formula of the roof strata was established.In combination with the site engineering practices,the paper analyzed the stability of the roof strata with different lithology and structure compositions in consideration of the multi factors.The roof falling hidden danger division of the gateway was obtained.The results showed that in a different area of the same gateway,the roof falling hidden grade would be different.Taking the stable rock stratum layer as the index of the roof falling hidden danger grade,the index could be divided into four grades,as Ⅰ,Ⅱ,Ⅲ and Ⅳ.The integrated stability of the roof in the test gateway was medium and would be Ⅱ grade area mainly which was taken 77.76% of the total length of the gateway.The highest Ⅳ grade area of the roof falling hidden grade was located in 668—740 m of the gateway,which was taken 9.47% of the total length of the gateway.In this section,the possibility of the roof falling accident occurred would high and the section should be a key monitoring and measuring area.