Analysis Of Stability In Underground Engineering Based On Convergence-confinement Theory

As one of important fields of modern engineering, the main feature of underground engineering is that the formation of structure through excavation,supporting and other aspects in situ stresses field.The structure bearing load from the deformation of surrounding stratus,while the deformation of structure constrained to the stratus.Most of current design methods in tunnel engineering are based on the rock mass classification,the numerical used as supplement for get the condition of stress-strain.compared to the maturity of characterization index in the stability analysis of ground structure, the design method of underground supporting structure which lacks of stability index of definite physical meanings, regard to the deficiencies in combination convergence-confinement theory to conduct research.The method for calculating the coefficient stability of underground structure based on the theory of convergence-confinement, which are mainly related to the ground and support. As the complexity and uncertainty in the existing environment and deformation mechanism of rock mass, the ground characteristic curve was used to describe the mechanics mechanism and deformation characteristics of rock mass.Then the building of supporting was relatively fixed(using bolt, shotcrete, steel and other supporting materials to build). According to the basic principles and important factors of convergence-confinement, the specific contents were as follows:Firstly, based on the domestic and external theoretical achievements about the the theory of convergence-confinement, a comprehensive overview of its basic principles and main constituent elements has been made.Its research status and development history also have been summarized.The classic circular cavern was selected for elastic-plastic analysis.The Kastner formula based on the theory of elastic-plastic and the Duncan formula based on the incremental theory of plasticity were selected to establish ground characteristic curve.Secondly, the rock mass mechanism and the respective mechanical properties of support unit were analyzed, the supporting characteristic curve of typical anchor and shotcrete support was established, and the joint stiffness equation, the maximum support pressure equation and support characteristic equation of anchor and shotcrete support were identified.Further, on the premise of the ground characteristic curve and support characteristic curve were established,synthesized the other component factors ofconvergence-confinement theory,the stability coefficient of supporting structure was derived in accordance with the principle of load method and graphic method.the implementation process of new method was demonstrated through with project example,the influence of rock mass mechanical parameters on the stability coefficient were analyzed, the otherness between different stability coefficients also analyzed through the example which under the similar conditions for rock mass mechanical parameters.Lastly, the program of indoor model tests were conducted, the research on the mixture ratio design of similar materials, strength analysis, simulation of different types of formations, measurement of stress- strain distribution after excavation, etc.,the experimental data were analyzed and verified in combination with theory.