Abstract
To reveal the critical factors of the main roof influencing stability of surrounding rocks of roadways driven along goaf in fully-mechanized top-coal caving faces, this paper builds a structural mechanics model for the surrounding rocks based on geological conditions of the 8105 fully-mechanized caving face of Yanjiahe Coal Mine, and the stress and equilibrium conditions of the key rock block B are analyzed, and focus is on analyzing rules of the key rock block B influencing stability of roadways driven along goaf. Then, the orthogonal experiment and the range method are used to confirm the sensitivity influencing factors in numerical simulation, which are the basic main roof height and the fracture location, the length of the key rock block B, and the main roof hardness in turn. It is revealed that the basic main roof height and its fracture location have a greater influence on stability of god-side entry driving. On the one hand, the coal wall and the roof of roadways driven along goaf are damaged, and the deformation of surrounding rocks of roadways and the vertical stress of narrow coal pillars tend to stabilize along with the increase of the basic main roof height. On the other hand, when the gob-side entry is located below the fracture line of the main roof, the damage caused by gob-side entry is the most serious. Therefore, on-site gob-side entry driving should avoid being below the fracture line of the main roof. At last, industrial tests are successfully conducted in the fully-mechanized top-coal caving faces, 8105 and 8215, of Yanjiahe Coal Mine.
Highlights
Adoption of the narrow coal pillar gob-side entry driving technique can efficiently increase recycling efficiency of coal resources and control effect of surrounding rocks of roadways. e technique has been widely used in China, but stability of surrounding rocks of roadways driven along goaf has limited further development of the technique [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]
E above analysis suggested that stability of the key rock block B could directly influence stability of the large structure of roadways driven along goaf and indirectly influence the stress environment of the small structure. e former mainly adopted theoretical analysis and quantitative experiments to analyze stability of the large structure of roadways driven along goaf, while the latter mainly analyzed influence of factors, such as support parameters, on stability of surrounding rocks of roadways based on numerical simulation
(2) When the fracture line of the main roof is outside the narrow coal pillar, Under the condition, there is no FM on the block B vertically, and the stress changes as follows: RAB + FD + FG − 2RBC − FR − FZ 0
Summary
Adoption of the narrow coal pillar gob-side entry driving technique can efficiently increase recycling efficiency of coal resources and control effect of surrounding rocks of roadways. e technique has been widely used in China, but stability of surrounding rocks of roadways driven along goaf has limited further development of the technique [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. Advances in Civil Engineering mining faces; Zhang et al [11, 12] analyzed four different Chinese coal mining sites and evaluated the influencing factors; Meng and Li [13] studied parameters’ sensitivity of bolt support in gob-side entry driving and found that the main influence parameters were bolt pretightening force and bolt interval; Yuan et al [14] studied the dynamic effect and control mechanism of key strata in the immediate roof; Bai et al [15] studied the stress state and the deformation failure mechanism of the heading adjacent to the advancing working face roof structure; Li et al [16] studied the in situ stress distribution characteristics of the rock mass near different slope angles’ hillslope surfaces; Wang et al [17] studied the stability of the concrete artificial side introduced to stabilize a gob-side entry. In view of the research gap, this paper built a structural mechanics structure for surrounding rocks of the key rock block B to quantitatively analyze influence of main roof factors on stability of surrounding rocks. Research findings are successfully applied to the 8105 working face and further promoted in the 8215 working face. erefore, research results of this paper can contribute to popularization of gob-side entry driving technique under similar geological conditions
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