Stability analysis of roadway surrounding rock under the action of bolt bearing layer

The existing method of controlling the stability of roadway surrounding rock is to apply the bolt support resistance to the roadway surface uniformly. But there are few research on the equivalent support force of the bolt bearing layer formed by the coupling of the bolt and the surrounding rock. By analyzing the surrounding rock mechanical model, the analytical expression of the equivalent supporting force of the bolt bearing layer and the analytical expression of the stress in the elastic zone and the plastic zone of the roadway surrounding rock under the action of bolt bearing layer, the radius of the plastic zone and the surface displacement of roadway surrounding rock are obtained. The analysis results shows the following three points. ① The bolt bearing layer thickness increases when the bolt length increases. The bolt bearing layer thickness decreases with the increase of the bolt row spacing when the bolt length is fixed. The bolt bearing layer equivalent support force increases when the bolt bearing layer thickness increases. ② In the plastic zone, compared with the Fenner solution that without considering the bolt bearing layer, the tangential stress of the surrounding rock increases significantly with this solution that considering the bolt bearing layer, and the peak stress position is closer to the center of the roadway. In the elastic zone, compared with the Fenner solution, the tangential stress of the surrounding rock decreases and the radial stress increases with this solution. ③ With the increase of the equivalent support force of the bolt bearing layer, the radius of the plastic zone decreases. With the increase of the equivalent support force of the bolt bearing layer, the surface displacement of the roadway surrounding rock with the Fenner solution and this solution decreases, and the displacement change with the Fenner solution is larger than that of this solution. The Flac3D software is used to numerically simulate the stress of the roadway surrounding rock under the action of the bolt bearing layer, the radius of the plastic zone and the roadway surface displacement. The numerical simulation results are basically consistent with the analysis results of the calculation example, and the stability of the roadway surrounding rock under the action of the bolt bearing layer is more reliable.