Study On Creep Fatigue Characteristics And Prestress Loss Law Of Anchored Jointed Rock Mass

The deep geological environment is complex,and the anchoring mechanism of jointed rock mass is not clear,which restricts the development of deep underground engineering.To explore the shear timeliness mechanism of deep anchored jointed rock mass under complex stress path is a key scientific problem to ensure the safety and stability of deep surrounding rock.Most of the underground engineering stress environment is complex: some tunnels are frequently earthquake prone,fault fracture zone is relatively dense,and blasting operation is widely used in excavation,so blasting disturbance has great damage to surrounding rock support structure.The deep fault fracture zone and roadway surrounding rock have obvious creep characteristics,and the deformation has significant timeliness.The effect of bolt anchoring to control the stability of surrounding rock is prominent and has a wide range of applications,but the mechanical mechanism between bolt and jointed rock is difficult to accurately grasp,and the mechanical behavior of anchored jointed rock is not clear.Therefore,it is of great significance to explore the anchoring mechanism of deep jointed rock in complex environment to improve the anchoring theory and solve the practical problems of support engineering.In order to explore the shear creep characteristics and prestress loss law of anchored jointed rock mass under creep fatigue load,the creep characteristics of anchored jointed rock mass under prestress were studied by changing the fatigue frequency,fatigue amplitude and fatigue times in fatigue load,using indoor macro test,theoretical analysis,CT scanning micro test,field monitoring and other methods.The main results are as follows:(1)When the normal stress is constant,the creep deformation decreases with the increase of the rock strength,and the peak strength of the specimen is positively correlated with the rock strength,while the creep failure time is not greatly affected by the rock strength;When the rock strength is constant,the peak strength and creep failure time increase with the increase of normal stress,while the shear creep deformation decreases.(2)In addition to the three typical stages in the conventional shear creep test curve of rock mass with anchored joints,the test curve of rock mass with anchored joints under creep fatigue load also includes the fatigue creep stage with inverted "V" type change,which makes the mechanical properties of the specimen change greatly,that is,the peak strain,shear strength,shear strength and shear strength of the shear creep test under different fatigue loads The failure time and shear modulus were changed.(3)The curve of prestress loss shows three stages: the rapid decline of prestress,the stability of prestress and the fatigue of prestress,and the prestress loss shows an upward trend under different fatigue loads,which indicates that the fatigue load will affect the deformation and failure of anchored rock mass,and then affect the prestress loss,The grey strip method is used to find out the initial value of prestress which is the main controlling factor of prestress loss.(4)Through the analysis of the prestress strain and stress-strain curves,the critical value of the anchorage rock mass in the stable state under the shear action is found out,and when the stress state of the specimen is in front of this point,the specimen will produce elastic deformation and be in the stable state;When the stress state of the specimen is at this point,the specimen is in the critical stable state;When the stress state of the specimen is beyond this point,the specimen will appear irrecoverable plastic deformation,and with the continuous action of the external force,the specimen will be destroyed.(5)By considering the main controlling factors of prestress loss,it is introduced into the traditional Xiyuan model,and combined with the damage law of fatigue load on anchored jointed rock mass,a constitutive model describing the whole process of shear creep creep of anchored jointed rock mass is constructed,and the accuracy of the model is verified by combining with the test data,which provides the basis and theoretical support for surrounding rock support.This paper has 72 pictures,19 tables and 78 references.