Mechanical Analysis And Stability Control For Deep And Shallow Bearing Structure Of Soft And Broken Roadway Surrounding Rock

As the continuous in-depth development of coal mining. engineering and geological environment that roadway surrounding rock in has become extremely complex. Rock mass shows properties of soft rock, and rock mass is very broken with a high ground stress, thus, the roadway is extremely difficult to support. In order to effectively control the deformation of soft and broken surrounding rock. it is essential to have a in-depth research on bearing structures and supporting theory of surrounding rock.In this paper, considering the engineering and geological characteristics of soft and broken surrounding rock, methods such as theoretical analysis, numerical simulation and engineering practice were used to research the bearing structure of surrounding rock. With considering rock mass strength, stress and deformation characteristics after roadway excavation, theoretical model was established to deduce the analytical solutions of stress field and displacement field in elatic zone,plastic zone and broken zone respectively, the radius of plastic zone was also given. To reveal deformation laws of soft and broken surrounding rock, influential factors such as post-peak strength softening, dilatancy effect, in-situ stress and support resistance were analyzed through examples. The surrounding rock bearing structure was spatial divided into deep and shallow bearing layer with comprehensively considering regional distribution of rock mass strength, stress and deformation characteristics. The shallow bearing layer is the broken zone surrounding rock, its strength is in the residual strength state, while the deep bearing layer is the entire softening zone surrounding rock and elastic zone that the tangential stress is higher than1.2times of in-situ stress. Analysis were given through examples to reveal effects of rock residual strength and support resistance on evolution of deep and shallow bearing structure and deformation of surrounding rock.FLAC3D numerical simulation program was used to analyze the evolution characteristics of deep and shallow bearing structure and deformation of surrounding rock. Study results show that bearing structure will particularly obvious with a large residual strength. Dilatancy effect occurs in softening zone of deep bearing layer, but it ultimately results in deformation of shallow bearing layer, forcing surrounding rock move toward free face. With increase of in-situ stress. thickness of deep and shallow bearing structure expand at different degrees. Four different support schemes were numerical simulated, the study indicates that combined support scheme of anchor net spray and cable with grouting can promote the formation of a whole bearing structure. which plays an important role in developing the overall bearing capacity of deep and shallow bearing structure in surrounding rock.The research results of theoretical analysis and numerical simulation were engineering applied to soft and broken surrounding rock, and field observations indicate that the effect of supporting, Theory of deep and shallow bearing structure was successfully applied in engineering practices.