Research On Triaxial Macro And Micro Damage Failure Mechanism Of Layered Rock Mass And Its Engineering Application

Layered rock mass is an anisotropic rock mass commonly encountered in underground engineering construction such as mine,water conservancy,traffic and tunnel,and the surrounding rock at different locations of underground engineering may be subjected to complex stress states such as compression,tension and even repeated loading and unloading.Coupled with the particularity of the anisotropy of layered rock mass,the research on the fracture evolution process and disaster mechanism of the layered rock mass under different stress states is insufficient,and the asymmetric large deformation failure and roof collapse of surrounding rock in layered rock mass construction of underground engineering occur frequently.Therefore,funded by National Natural Science Foundation Key Projects of China（51734009）,this thesis takes Yunji Tunnel in Liuzhou City,Guangxi Province as the engineering background,and the research methods of micro observation test,macro mechanical test,theoretical analysis,numerical simulation and field test are comprehensively adopted.The macro and micro mechanical properties,energy evolution characteristics and fracture evolution mechanism of layered rock mass under triaxial complex stress state are studied in depth and systematically.The main achievements are as follows:（1）Using 98 pieces of layered rock-like material specimen prepared by independent design method,uniaxial compression test,Brazilian tensile test,triaxial compression test,triaxial unloading confining pressure test,triaxial cyclic loading and unloading test are carried out to obtain the influences of bedding plane inclination angle,confining pressure,initial unloading level and fatigue load amplitude on the macro mechanical properties.It also provides a basis for the study of micro fracture evolution mechanism and constitutive model.（2）Based on the macro mechanical tests of layered rock mass under different triaxial stress paths,acoustic emission monitoring,digital photography,and CT scanning are combined to construct the quantitative relationship between acoustic emission characteristic parameters,morphological characteristics of macro and micro cracks,energy evolution and mechanical properties of layered rock mass.The macro and micro fracture evolution mechanism and regularity of layered rock mass under different stress paths are illustrated.（3）It is found that the mi value changes obviously with the increase of bedding plane inclination angle and confining pressure.Therefore,the improved Hoek-Brown strength criterion is proposed by fitting the mi value function relation of bivariate cubic polynomial function considering the bedding plane inclination angle and confining pressure.Based on475 groups of triaxial compression test data of layered rock mass,it is found that the improved Hoek-Brown strength criterion is effective in predicting the triaxial compressive strength.（4）Based on the improved Hoek-Brown strength criterion and the damage factor with equivalent plastic strain as the variable,the anisotropic damage constitutive model of layered rock mass is established by using the correlated flow law.Through secondary development,the established constitutive model is written into FLAC^3D software,and the numerical simulation of triaxial compression test of layered rock mass is carried out.The simulation results show that the developed constitutive model can reflect the anisotropy of layered rock mass effectively.（5）FLAC^3D software is used to analyze the deformation characteristics of layered rock mass tunnel surrounding rock.By comparing with the field test results,it is verified that the developed constitutive model is suitable for the study of deformation and failure of layered rock mass tunnel surrounding rock.Furthermore,the influences of bedding plane inclination angle,buried depth and arch bolt length on the deformation of tunnel surrounding rock are analyzed.Based on the numerical simulation results,the optimization scheme of engineering test section is proposed,and the industrial test is carried out.Good supporting effect is obtained.This thesis has 113 figures,35 tables and 172 references.