Study On Creep Properties And Damage Constitutive Model Of Sandstone Under Complex Environment

Underground engineering faces many challenges in the process of excavation and support.From the perspective of internal factors,as the excavation depth gradually extends to the deep,underground temperature is higher,which has a particularly prominent influence on rock stability and mechanical characteristics,mainly manifested in: With the increase of temperature,the mechanical properties and bearing capacity of rock will decrease to some extent,resulting in the deterioration of rock mechanical properties.From the external environment,in engineering practice and nature,deep tunnel excavation will be affected by disturbance loads such as blasting,which is characterized by short action time,high action intensity and fast action frequency,and disturbance loads will have a great impact on the stability of geotechnical engineering.Therefore,it is of great significance to explore the mechanical characteristics of deep rock mass in complex environment to improve the theory of surrounding rock support and solve the practical problems of support engineering.This paper to explore complex environments such as confining pressure,temperature and disturbance load under the action of sandstone creep mechanics characteristics and the corresponding deformation law,through the development of the temperature influence on sandstone under different confining pressure triaxial compression test,the corresponding mechanics mechanism of sandstone,and then to carry out the temperature under the influence of different disturbance load disturbance amplitude and disturbance(frequency)of sandstone under triaxial compression test,Finally,the rheological constitutive model of sandstone under different temperatures and disturbed loads was constructed according to the relevant test contents,and the deformation and failure types of sandstone were analyzed by using numerical simulation software.The main results are as follows:(1)The conventional triaxial compression creep curve includes decay creep,stable creep,metastable creep and accelerated creep stages.In the conventional triaxial compression test,the instantaneous creep deformation decreases gradually with the increase of confining pressure.(2)In the triaxial compression creep test of sandstone under different temperatures,when the temperature is constant,the creep deformation values of various levels rise gradually with the increase of stress level,and the curve approximately shows a linear change trend at low stress level,while the nonlinear characteristics are obvious at high stress level.Considering the damage changes of sandstone caused by temperature,the Nishihara model was modified based on Weibull distribution,and the creep damage constitutive model of sandstone under the influence of temperature was obtained.The experiment verified that the model could describe the acceleration stage that Burgers and other components could not represent.(3)The variation law of creep variables before and after each disturbance at different disturbance amplitudes and frequencies: the higher the disturbance amplitude and frequency are,the larger the creep variable is,and vice versa;With the gradual increase of stress level,creep increment under disturbed load presents a trend of gradual decline.(4)when stress level is low,only attenuation stable stage and steady-state stability stage,specimen to stress in three appear only original crack under the action of pressure and the production of new fractures,when stress level is higher,the specimen accelerated creep stage,when the inside of the specimen fracture gradually through until a new macro fracture.Disturbance of load applied to sandstone internal crack propagation have influence,under low stress level,the specimen interior still has high strength,makes the load cannot fully play to the role of the disturbance of load disturbance,and when the stress level rises,the specimen within the new pores or fracture,specimen in a certain degree of damage,enables the disturbance of load to play a role of large disturbance.(5)Based on the triaxial compression creep test under the influence of temperature and the triaxial compression creep test under the influence of disturbance load,on the basis of the influence of temperature,by considering the influence of disturbance load on the deformation characteristics of sandstone,the new nonlinear element is introduced to describe the mechanical characteristics of sandstone.The nonlinear element considering the disturbance load is connected in series with the Nishihara model considering the attenuation and steady-state characteristics of sandstone under the action of temperature,thus a constitutive model describing the rheological characteristics of sandstone under the complicated environment of temperature and disturbance load is established.This paper has 66 pictures,127 tables and 140 references.