Study On Dynamic Stability And Time Series Analysis Of Tunnel Surrounding Rock

As the dominant engineering of inter-provincial highways from Changsha to Wulong of Chongqing in Western Development, Baiyun Tunnel, characterized by complex geological conditions, deep, long etc., bad geological phenomenon, such as broken belt, fold, karst region, unveiling coal, gas and other harmful gases, will be encountered in the period of construction. Further systematically study the dynamic instability and the mechanism of rock failure in tunnel with complex geological conditions has very important practical significance.In this paper, through researching the physical and mechanical properties in laboratory and insitu tests during the tunnel excavation, analysis of dynamics theory, numerical simulation of the whole process of tunnel excavation, the sinking arch ARMA time series modeling and forecasting analysis, we can obtain some conclusions as follows:(1)a. All types of rock in Baiyun Tunnel having higher stiffness and intensity, elastic wave velocity of limestone is 2,500~4,900m/s and that of mud stone and shale is 2,100~3,700 m/s. The integrity coefficient of rock is 0.56~0.78, proving better integrity.(2)Using self developed quasi-planar strain load equipment , study the deformation localization failure mode of shale in the plane strain state under the condition of the same moisture content, different loading speed and different moisture content, the same loading speed separately, having acquired the logarithm relation and the form of shear band(3)Using self developed triaxial creep test system, experiments of unloading confining pressure creep on shale in the Baiyun Tunnel was conducted to study the mechanism of instability breaking during the unloading process when the tunnel is excavated. The experiment result shows that the unloading level have great effect on the stability of rock, lower unloading level result in larger deformation and shorter time before the deformation speeding up. The research result has an important practical project significance to determine the way of excavation and the relative time of the initial support of the Baiyun Tunnel.(4)Simplifying the overlying strata of tunnel into two-parameter elastic-plastic foundation beam mechanical model, through mathematical derivation and analysis of mechanics we can acquire the specific form of the deflection differential equation of the overlying strata of vault and the elastic foundation beam of the tunnel surrounding rock deformation. Derive the expression Sinking speed of vault and explain the deformation of tunnel surrounding rock theoretically;(5)In view of the characteristic of Baiyun Tunnel , select typical cross-section of the section of deep, shallow and fault fracture zone to make static and dynamic analysis and acquire the evolution of stress, initial lining and the working conditions of bolt during the of the whole process of the tunnel construction under four types project conditions.(6)Making use of basic ideas of dynamic time series and the basic principles based on stationary processes autoregressive moving average (ARMA) model, simulated the vault deformation of the YK46 +180 cross-section, developed prediction model of vault sinking displacement based on the autoregressive moving average (ARMA) model and autoregressive (AR) mode, and the actual calculation shows that the accuracy is higher than the static modeling.