Study On The Mechanics And Acoustic Emission (AE) Characteristics Of The Deformation And Failure Of Rock Under Deep Ground Excavation Disturbance

Deformation and fracture of surrounding rock is induced by the engineering disturbance to a large extent and leads to an amount of serious engineering disasters.Hence,it is the key problem to reveal the mechanical behaviors and damage characteristics of rock under engineering disturbance.In this thesis,focused on the damage characteristics of rock under engineering disturbance,the process of deformation as well as the macro-micro failure characteristics are studied by rock mechanical test,3D scanning,acoustic emission monitoring,fractal theory,finite deformation theory and constitutive theory,and the elasto-plastic constitutive model of rock considered disturbance modes is also established and verified.The main conclusions are as follows:(1)Analyzing the mechanical behaviours of rock under the disturbance stress paths.The rock mechanical tests are designed and conducted under the different initial confining pressure(12.5 MPa,25 MPa,and 37.5 MPa)and disturbance modes(low disturbance,medium disturbance,and high disturbance).The results shows that both the initial confining pressure and disturbance mode can have a significant effect on the basic mechanical parameters of rock.Meanwhile,the effect of initial confining pressure is higher than that of disturbance mode.Under the initial confining pressure of 12.5 MPa and 25 MPa,dissipated energy can be influenced seriously and moderately by the disturbance mode,respectively.Under the initial confining pressure of 37.5 MPa,it can be found that disturbance mode can hardly affect dissipated energy.Then,the arithmetic mean deviation and maximum height of fracture surface increase with the degree of disturbance according to the 3D scanning.Finally,it can be observed that the fractal dimension of fracture surface increases with the degree of disturbance.(2)Revealing the temporal-spatial distribution of AE activities and associated fractal characteristics of rock under the disturbance stress paths.During the hydrostatic stress stage,it can be found that the duration of moderate stage of cumulative AE energy and count from least to most in proper order is: 12.5 MPa,25 MPa,and 37.5 MPa.Then,during the disturbance stage,the “sensitive effect”,“inferior sensitive effect” and “delayed sensitive effect” of the disturbance mode can be observed through the temporal-spatial distribution of AE activities under the 12.5MPa,25 MPa,and 37.5 MPa,respectively.Additionally,the fractal dimensions of the temporal-spatial distribution of AE activities show rapid increase and dramatic decrease within some specific conditions.Finally,it can be inferred that the damage characterictis of rock is in well accordance with the “sensitive effect”,“inferior sensitive effect” and “delayed sensitive effect” respectively under the 12.5 MPa,25 MPa,and 37.5 MPa.(3)Establishing the strength criterion and elasto-plastic constitutive model of rock under the disturbance stress paths.The mean rotation angle of rock is firstly calculated based on the finite deformation theory under the disturbance stress paths.It can be found that both the initial confining pressure and disturbance mode can significantly influence the mean rotation angle,and the effect of initial confining pressure is larger than that of disturbance mode.Then,a damage variable based on the mean rotation angle is presented and the Hoek-Brown strength criterion considered the intermediate principal stress(3D Hoek-Brown strength criterion)is improved by such a damage variable.And the prediction of novel 3D Hoek-Brown strength criterion is discussed in the deviatoric plane.Finally,based on such a novel 3D Hoek-Brown strength criterion and a hardening function considered disturbance mode and mean rotation angle,an elasto-plastic constitutive model under the disturbance stress paths is established and varified.