Abstract
Based on the 211113 “short face” of Xinji No. 2 Mine of China Coal Group, this study investigated the weakening regularity of blasting vibration and rock bursting of roof through FLAC3D numerical simulation on the basis of the hard roof fracture regularity through theoretical analysis. The results show that the vibration frequency of the hard roof increases linearly with the increase of the distance from the source, and the vibration amplitude decreases exponentially with the increase of the distance from the source within 20 m from the blasting relief hole. Based on the above results, from the three indexes of controlling the amplitude, frequency and duration of pressure relief blasting vibration, it is proposed that the roof on the 211113 “short face” needs to be controlled by the advanced overlying strata weakening technology, and the parameters of advanced deep hole pre-splitting blasting are optimized. After the roof was weakened by the advanced deep-hole pre-splitting blasting, it can basically fall with mining. The blasting method can effectively avoid the phenomenon of large-area “hanging arch” and effectively prevent the occurrence of rock burst.
Highlights
Huainan coalfield is one of the most representative coalfields in central China [1]
Due to the short length of the 211113 “short face” and the extra hard and thick quartz sandstone in the overlying roof, with the advancement of the working face, the principal area of stress concentration is mainly located at the hard roof with very limited roof subsidence and failure scope
After the advanced weakening roof technology is adopted to effectively weaken the “short-face” overlying strata, the principle stress distribution of surrounding rock in the stope has been greatly improved, and the overlying strata fall in time with the mining of the working face
Summary
Huainan coalfield is one of the most representative coalfields in central China [1]. Its minable coal seams are usually covered by hard and thick rock strata with high strength, while it is often hard for extra thick and hard roof to fall with mining in coal seam mining process [2]. Due to the wide range of overlying strata fracture, It is necessary to further study the weakening law of vibration and impact rock breaking during the process of pressure relief by borehole blasting of “short face” huge thick and hard roof, as well as the effect and influence on coal and rock mass damage and stope rock pressure. In this way, a reasonable overlying strata step of ultra-short-face mining and roof management technology can be determined to ensure the safe and efficient recovery of ultra-short working face. In this paper, taking the 211113 working face of Xinji No 2 mine of China Coal Group as the research background, the study investigated the roof rupture regularity through the theoretical analysis and the FLAC3D numerical simulation method, and for the “short-face” hard roof, Besides, it carried out field tests of roof weakening by advanced deep-hole blasting to verify the rationality and practicability of the method in solving the problem of “short-face” hard roof
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