Study On Surrounding Rock Controlling Technology For Coal Roadway In Xuchang Coal Mine

A non-linear rheologic model of surrounding rock of roadway was established with combination models of elastic-plastic-vicosity elements on the basis of Xuchang Coal Mine's 4302 track roadway's geological conditions. It's theoretical basis is the attenuation characteristics of long-period strength and strain energy conservation law of rock. The deformation of surrounding rock was evaluated by this model. The evaluating results reveals that the deformation law of surrounding rock achieved by non-rheologic model fits the field test well. At the beginning, the deformation velocity is fast, then slow with time. It confirmed that the non-rheologic model is adapted to 4302 track roadway's conditions. In- time supporting technology and active supporting was recommended according to the estimated surrounding rock's deformation law.The coal roof of 4302 rail roadway in Xuchang mine is soft and broken, with a big thickness of its unstable layer and well developed fractures, making it very easy to fall in the process of roadway excavation. Aiming at this problem, we have suggested four support countermeasures, which are 1) reducing roof exposing distance, 2) reducing roof exposing time, 3) increasing setting pressure of temporary lining, and 4) using prestressed bolt- mesh-anchor support. The specific support scheme is reducing circle footage, having a strong temporary lining, adopting laevorotatory and high performance prestressed screw—thread steel bolts, and strengthening support with small aperture short anchor rope.This new support scheme was compared with the original scheme in surrounding rock controlling situation using numerical simulation, indicating that 1) It's dominant in roof sinkage during surface displacement. 2) the shape of stress distribution is same, and the stress distribution is similar. Coefficient of stress concentration changes a little, but the stress affected zone is reduced.3) The plastic zone is reduced whether excavating or mining period, so the surrounding rock is reinforced. 4) The stress state in surrounding rock is improved, the plastic zone reduced,and the surface displacement of surrounding rock controlled effectively. Based on this analysis, the optimal support plan is confirmed and applied in practice.The actual measurement shows that, by using the new support scheme, the roadway is well shaped and the deformation is effectively controlled.