Abstract
In coal mining roadway support design, the working resistance of the rock bolt is the key factor affecting its maximum support load. Effective improvement of the working resistance is of great significance to roadway support. Based on the rock bolt’s tensile characteristics and the mining roadway surrounding rock deformation, a mechanical model for calculating the working resistance of the rock bolt was established and solved. Taking the mining roadway of the 17102 (3) working face at the Panji No. 3 Coal Mine of China as a research site, with a quadrilateral section roadway, the influence of pretension and anchorage length on the working resistance of high-strength and ordinary rock bolts in the middle and corner of the roadway is studied. The results show that when the bolt is in the elastic stage, increasing the pretension and anchorage length can effectively improve the working resistance. When the bolt is in the yield and strain-strengthening stages, increasing the pretension and anchorage length cannot effectively improve the working resistance. The influence of pretension and anchorage length on the ordinary and high-strength bolts is similar. The ordinary bolt’s working resistance is approximately 25 kN less than that of the high-strength bolt. When pretension and anchorage length are considered separately, the best pretensions of the high-strength bolt in the middle of the roadway side and the roadway corner are 41.55 and 104.26 kN, respectively, and the best anchorage lengths are 1.54 and 2.12 m, respectively. The best anchorage length of the ordinary bolt is the same as that of the high-strength bolt, and the best pretension for the ordinary bolt in the middle of the roadway side and at the roadway corner is 33.51 and 85.12 kN, respectively. The research results can provide a theoretical basis for supporting the design of quadrilateral mining roadways.
Highlights
The results show that when the bolt is in the elastic stage, increasing the pretension and anchorage length can effectively improve the working resistance
In a high-stress environment, the mining roadway often shows the characteristics of large deformation, so the deep mining roadway often requires higher support strength
As the key parameters of the bolt support design, anchorage length and pretension have a direct impact on the working resistance
Summary
Based on field engineering practice, physical experiment results, and theoretical reasoning analysis, many scholars at home and abroad have carried out in-depth research on anchorage length and pretension from different angles, and have achieved certain research results These results are only applicable to circular, oval, and other regular cross section roadways. Based on the bolt tensile curve and the surrounding rock displacement distribution, the mechanical model can comprehensively reflect the influence characteristics of pretension, anchorage length, roadway cross section shape, surrounding rock stress conditions, and surrounding rock lithology on the bolt working resistance. Taking the 17102 (3) working face mining roadway at the Pansan Coal Mine in the Huainan mining area as the engineering background, the influence of pretension and anchorage length on the working resistance of the high-strength bolt and the ordinary bolt in the middle of the roadway side and the roadway corner in the quadrilateral section roadway is studied. This paper summarizes the research results and provides conclusions
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