Study On Creep Behavior And Long-term Strength Of Argillaceous Siltstone Under High Stress

With the rapid development of the economy,China's construction has also been expanding,especially the proposal of 'Western Development'.There are a large number of roads and railway tunnels built in the mountainous areas of southwest China.The scale of the project is larger than before,and the environment is also More complicated,the problems are also more in-depth,especially,Deep tunnel Often Collapse,which makes people realize the complexity of rock mechanics.Based on the previous studies,this paper selects the argillaceous siltstone excavated by a deep buried chamber,study the creep characteristicsand long-term strength of the argillaceous siltstone under high stress,research achievement is helpful to give the branch of the deep buried chamber.Provide guidance on design and evaluation of its long-term stability.The study obtained the following research results.1)Through the triaxial creep compression test,combined with the existing research data on rock creep properties,Analyzesd the creep characteristics and creep failure mechanism of argillaceous siltstone under high stress.2)By separating the viscoelastic creep and the viscoplastic strain in the creep of rock,under the action of high stress,the argillaceous siltstone not only has viscoelastic deformation in the decay creep stage,but also has viscoplastic deformation and stickiness.The relationship between plastic deformation and time is gradually increased in a nonlinear form.Therefore,in studying the nonlinear characteristics of rock creep under high stress,the viscoplastic deformation in the decay creep stagealso should be considered.3)By breaking the strain,the damage equation of the rock,the damage equation of the viscoelastic parameters and the viscoplastic viscous coefficient function are substituted into the constitutive model,and the modified variables are introduced based on the damage theory.The improved model can reflect the high stress perfectly.The nonlinear characteristics of the entire creep process are better.4)separate the creep of the argillaceous siltstone which are pressed by high stress According to the research,the viscoplastic creep not only exist in the accelerated creep stage,but also exists in the previous decay creep stage.The accumulation of viscoplastic creep resulting in the accelerated creep damage of rock,the steady-state viscoplastic creep rate can be used as a reference to judge the long-term strength of rock.Based on this theory,I propose a way that is the steady-state viscoplastic strain rate method,and the shale siltstone under high stress is obtained.The long-term strength value is 64.82 MPa,which accounts for about 70%of the uniaxial compressive strength.