Research On The Creep Property And Its Stability Control Technology Of Gob-side Entry's Narrow Side

The long-term stability feature of the gob-side entry's narrow side directly affects its overall stability and it is also difficult to successfully develop the pillarless mining technology. Taking the time effect research of stability of the gob-side entry's narrow side as a pointcut, law of the stress and deformation, creep property, failure criterion and stability control technology of the narrow side based on four species main roof's fracture forms, have been systematically analyzed by theoretical analysis, physical simulation, numerical simulation, laboratory rock block experiment, and industrial experiment methods etc. Innovative achievements of this dissertation have been displayed as follows:(1) Based on the main roof's four species fracture structure form, the corresponding mechanical model of the stability analysis of the narrow side is established, and the calculation formula of the static load on the narrow side is derived, and the law between stress and deformation is clarified.(2) The numerical analysis of the dynamical effect shows that the dynamical effect produced by the main roof's fracture and rotation mostly affects the stability of the narrow side. Whether the fracture line of the main roof located inside or outside of the narrow side, the stress and lateral deformation are the largest of its upper part, and this part is most likely to be destroyed firstly.(3) The self-defining nonlinear creep model and the constitutive equations of concrete artificial side are built. The concrete artificial side'shortest time of the creep failure was obtained based on the minimum potential energy principle. The creep limit load and creep failure load of concrete artificial side are proportional to its strength ratio. The strength of the artificial side should be increased 20%~30% and its appropriate aspect ratio should be in between 1 and 2 based on the creep property and size effect.(4) Twin shear stress function and twin shear strength theories were obtained after the orthogonal octahedron was adopted to analyze the stress of the concrete artificial side. Experiments verified that two sets of the shear stress together resulted in the failure modes of the concrete artificial side, and the distribution pattern of the maximum shear stress in the concrete artificial side accorded with its failure pattern appeared"X"shape.(5) Large-size creep experimental system with 10,000 kN was independently developed. The creep property experimental analysis on the Large-size artificial sides, Large-size artificial sides with anchor bolts strengthen, and Large-size artificial sides with different building ways, was carried out. The results show that the creep limit load and creep failure load of artificial side are inverse proportional to water-cement ratio. After being strengthened by the anchor bolts, the anchor bolts effectively constrained the progress of artificial side's lateral deformation, and expanded the artificial side's pressure district area, and improved the artificial side's overall bearing capacity and its stability. The stability of artificial side was closely related to its building ways, and the stability of integral building artificial side was stronger than that of blocking piled artificial side, and the stability of the soft-hard structure artificial side was stronger than that of hard structure artificial side.(6) The soft-hard structure effect mechanical model of narrow side was built, and the compatible deformation mechanism that the structure was coordinated with the roof and floor is explained. The upper soft structure can absorb the energy in the roof by its large deformation, and the artificial side's stress distribution characteristics is improved, and can adapt to the given deformation caused by the fracture and rotation and subsidence of main roof. The hard structure at the bottom of the backfill wall can afford the adequate supporting resistance, and the stability of the entire backfill wall is insured.The above research results were successfully carried out by the engineering application research at four typically experimental sites, and the satisfactory economic and social benefits were obtained, and can promote the use of the technology under the similar conditions.228 pieces of figures, 40 pieces of tables and 162 pieces of consult documents have been quoted in this dissertation.