Study On Deformation Characteristic And Statistiacl Damage Simulation Of Full Deformation Process For Rock

As rock is a typical brittle material containing flaws, its constitutive relation under complicated stress is a complicated basic theoretical question. Especially on the operation phase of rock engineering, the deformation characteristic will directly influence the normal use of engineering. Based on reasons above, the continuous damage theory, microscopic damage mechanics and the theory of probability have been integrated to reasonably evolve the damage variable on the basis of damage constitutive models of rock considering various loading conditions simulate damage constitutive models of rock under varied complex stress state and apply results to rock engineering.In the first place, based on the damage constitutive model of rock under Lemaitre’s hypothesis of strain equivalence, this paper discussed the necessity considering damage threshold to establish rock damage evolution model when exploring the law of damage variable or damage factor of strain softening deformation of rock, combined with the study of rock characteristics of strain softening deformation and mechanism of injury. On the existing rock micro-element strength measuring method, a new rock micro-element strength measuring method was put forward which could consider the impact of rock damage threshold. The statistical damage theory, and established the rock statistical damage evolution model which can weigh the impact of damage threshold of rock. This model can not only reflect the impact of damage threshold, but the damage degree by the influence of stress state and characteristics of varied damage starting point under varied stress states as well.Secondly, the volume change characteristic is a major concern in rock mechanics. Due to limitations and shortcomings of the current damage constitutive models of rock, this paper divided rock under stress into three parts:void, damaged and undamaged material. By using void ratio to reflect the rock volume or void changes, damage variable (or damage factor) to reflect the variable feature of rock mechanics, relationship between micro and macro stress and strain analysis of all parts of material has been analyzed. Then the new rock damage model has been established, which rock deformation is able to indicate the volume or void changes in size or characteristics. And the statistical damage constitutive model was built which can show the volume change characteristic of rock. Also the method determining its parameters was given. Based on this constitutive model, the determination approach on conditions of transforming brittleness into ductility of rock was offered by exploring the rock brittle mechanical properties and mechanism of mutual transformation and characteristics and the use of extreme value analysis to solve multi-function approach. This method is capable to display simultaneously the loading state of rock and its own mechanical properties’ influence on rock’s brittleness and ductility and their mutual transformation characteristics and perfected the research content of rock’s constitutive model.Furthermore, the process simulation of rock deformation and destruction of strain softening is one of significant branches of rock mechanics research. in the analysis of various characteristics at different stages of the Strain softening of rock deformation process, due to the shortcomings that the existing rock damage model failed to indicate rock’s residual strength properties after failure of rock, on the assumption that the loading rock is comprised of damaged and undamaged material and the axial load was shared by these two parts, the stress that damaged material bears is defined as residual strength, a new damage model was established showing rock’s residual strength after failure. Then on the basis of this model, statistical damage evolution model of rock was built showing the whole deformation process and the statistical damage constitutive model was developed simulating the whole process of rock strain softening, the determination of the model parameters was given as well. The project case verified w that the model can better reflect the residual strength after the peak stage of rock deformation.Finally, to improve the simulation of rock deformation research content, the dynamic deformation process of rock was simulated. According to the dynamic deformation characteristics of rock, the research methodology of Kelvin model was introduced. The dynamic stress during rock deformation was considered as the superposition of dynamic and static components of stress. By using viscous components and non-linear components to simulate dynamic and static stress components respectively, the mechanics analysis model for dynamic stress of rock was built. Based on this study, taking advantage of the mechanical properties of viscous components and statistical damage theory, the simulation of the deformation process of viscous and non-linear components was proposed and the simulation of rock triaxial dynamic deformation process was put forward, the determination of model parameter was included too. The analysis and discussion of project case justified the rationality and feasibility of this method.