| The geological conditions in the west of China are complex,and the tectonic development and fault division are wide.The underground tunnel in this region has some complex engineering geological problems,such as large buried depth,high in-situ stress and large stress difference,complex tectonic stress field,variable structural plane distribution characteristics,anisotropic of layered rock lithology,etc.,which lead to the severe situation in route selection and construction.Under the background of complex geological structure,the mechanical properties of layered rock mass are greatly affected by structural planes,and the failure mechanism and failure mode of layered rock mass after excavation and unloading are significantly different from those of other rock masses.Therefore,it is of great guiding significance to study the mechanical properties of surrounding layered rock of deep buried tunnels under high in-situ stress and evaluate the deformation grade.The research contents in this paper are mainly as following:(1)Combined with the field geological conditions and survey data,the engineering geological conditions of Duoji tunnel,Duomuge tunnel and Baokang tunnel of Zheng-Wan Railway of Sichuan-Tibet Railway were analyzed,mainly taking layered slates and shale as the research object,and the technical route of the study was drawn up.(2)Based on the coMParison results of the uniaxial and triaxial compression tests of slate under saturated and unsaturated conditions,the influences of the water-softening characteristics of slate and the significant anisotropy characteristics on the actual engineering construction are analyzed.(3)Based on the electron microscope scanning test results of shale,the damage surface characteristics of the shale with different stratification angles were analyzed from the meso-scale.Based on the short-term triaxial compression test and long-term creep test results of the shale with different stratification angles,shale mechanics deformation under confining pressure was studied from the macroscopic in terms of the long-term strength characteristics and the rheological characteristics of shale.(4)Through cyclic loading and unloading tests during shale creep process,the evolution of damage parameters and long-term mechanical properties in the creep process of shale were analyzed,which provided a reference for subsequent design,rock mass excavation and stability analysis.(5)Based on the mechanical deformation properties of the slate,physical properties test analysis,and the water-softening properties,the surrounding rock deformation mechanism of Duoji tunnel,Duomuge tunnel were analyzed.And combined with the engineering geological conditions of the region and tunnel route selection,the criterion ofsurrounding rock deformation was proposed by considering the stratification angle.Then,the threshold deformation at each levels were figured out for tunnel deformation classification.(6)With the application of numerical calculations in FLAC3d,the deformation and failure characteristics of layered shale was simulated to obtain the deformation and plastic zone evolution law of tunnel surrounding rock under different stratified angles.Combined with the actual monitoring data in site,the supporting timing and supporting mode are discussed and analyzed.Figure [54] Table [21] Reference [52]... |
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