The Safety And Stability Analysis Of Excavation Of Inlet Of Cavern Group In The Cen Tianhe Reservoir Expansion Project

With the focus of hydropower station development change to Southwest of china,the rough terrain,the complex geological conditions and many faults cause by plate movement make it very difficult to excavate and support tunnel in this area.Different excavation sequence and supporting time of adjacent chambers have an effect on the stability of the cavern group for the complex geological conditions and the interaction of the adjacent tunnel.Cen Tianhe Reservoir Expansion Project is the control engineering of Xiaoshui Cascade development,the surrounding rock of new outlet section at intake power generation tunnel is grade V.And there are several fault which fracture zone width from 1 to 3 meter through it.The rock is broken,the self-stabilizing conditions are poor,the self-stabilization problem of surrounding rock and tunnel face in outlet section is exist.In view of this,this paper takes the import caverns in centianhe river water conservancy hub expansion project as an example,ANSYS is used to establish the three-dimensional finite element model of the geological,consider the viscoelastic property of rock and soil materials to simulate the time-dependent properties of rock and soil materials,count on FLAC3 D platform,considering the excavation slope and the diversion power tunnel and 1# of spillway tunnel of different excavation sequence,different supports and protects the opportunity,the sensitivity factors of the mechanical parameters of rock mass,access to surrounding rock in the tunnel construction process of the stress,deformation and stability characteristics of information and engineering excavation and support to make a guiding significance for engineering design reference.The main research contents are as follows:(1)Based on plane elevation data,combined with geological data by drilling and on-site exploration,to get all the information rock about layered interface to construct a threedimensional model of outlet section in intake power generation tunnel.Use switched program to import the geological model into FLAC3 D to discrete it.(2)After selecting the elastic constitutive model,the boundary conditions are established,and the material parameters are set up.After calculating the equilibrium,the initial stress field is generated,and then the position and velocity field are cleared.After the slope excavation,calculate the displacement increment,stress,plastic zone of the inlet section of the inlet section of the tunnel,and pick better sequence of excavation between the diversion power tunnel and 1# spillway tunnel.(3)According to the selected optimal excavation sequence,calculate the corresponding displacement,stress and plastic zone for different support time,then chose the optimal support timing.(4)The elastic modulus,Poisson’s ratio,cohesive force,internal friction angle and tensile strength of the five parameters of the Flac3 D were sensitivity analyzed.Analyze the max displacement of the section when parameters changes.