Abstract
When gob-side entry retaining is adopted in mining face with large cutting height, due to large stope space, strong dynamic pressure and other reasons, the filling body is usually broken and unstable due to improper width of filling body, and the stability of surrounding rock of roadway is poor. Therefore, this paper will take Shaqu mine as the engineering background to study the reasonable filling body width of gob-side entry retaining in mining face with large cutting height. Firstly, the stability factors of gob-side entry retaining in mining face with large cutting height are analyzed, and the mechanical model of bearing structure of gob-side entry retaining is established based on the lateral pressure and overlying load of filling body, and the reasonable width of filling body is obtained quantitatively; Numerical simulation is used to analyze the evolution of vertical stress, vertical displacement and plastic zone of working face with the change of filling body width. Finally, combined with the deformation observation results of 24207 gob-side entry retaining roof, two sides and filling body, the rationality of filling body width is verified. The results show that: the setting of the width and strength of the filling body plays an important role in the stability of gob-side entry retaining. According to the mechanical model, the minimum width of the filling body is 2.2m in the lateral direction and 3.9m in the vertical direction; Numerical simulation shows that when the width of filling body is too small, with the increase of filling body width, the vertical stress of filling body increases gradually. When the width of filling body reaches a certain value, the vertical stress decreases with the increase of width, and the stress concentration area will change from symmetrical type to eccentric load type, from the middle of filling body to the side of filling body near gob. If the width of the filling body is too small, the filling body will be too broken to bear the load, resulting in too small vertical stress and too large vertical displacement of the roadway roof. The larger the width of the filling body is, the greater the cutting resistance is, the more timely the side roof of the gob can be cut off, the less the stress of the roadway and the filling body, and the more stable the retained roadway is. Finally, through the observation of 24207 gob-side entry retaining, the total deformation of two sides and roof and floor of roadway tends to be stable after 665mm and 597mm respectively. The roof of roadway does not appear severe subsidence and obvious cracking, and the floor does not appear too large floor heave. The effect of roadway retaining is good, which indicates that 4m support can meet the needs of practical engineering.
Evolution Laws of Mining-induced Stress in Floor Strata and Its Influence on the Stability of a Floor Roadway Affected by Overhead Mining
