Study On The Seismic Response And Shock Absorption Of Mountain Tunnel In High Intensity Region

In recent years,with the rapid development of the transportation industry,China has built many highway and railway tunnels in the mountains,which has promoted the people's life and economic development in remote areas of China.However,China is located between the Indian Ocean plate,the Eurasian plate and the Pacific Rim plate,the unique geographical location makes China a country with many earthquakes.Each strong earthquake will cause huge casualties and economic property losses.The Wenchuan Earthquake on May12^nd,2018,has caused many tunnels damaged to varying degrees,which seriously affected the rescue work after the disaster.It is especially important to study on seismic design and shock absorption of mountain tunnels in high intensity region.Based on the project of the Lanjiayan Tunnel shallow of Mian-Mao Highway,and combined with engineering geology,the dynamic finite element analysis software is used to analyze the seismic dynamic response.so,shock absorption measures are proposed for reference.The main research contents and achievements of the thesis are as follows:?1?On the basis of a large number of earthquake damage data of tunnels at home and abroad,the seismic damage typical,mechanism and influence factors were summarized.And then the basic method of dynamic analysis,damping matrix and boundary conditions are introduced,and the basic parameters used in the model are determined.?2?Inputting the intense earthquake?2%?along the lateral direction of the model,the dynamic response of the portal section of tunnel is analyzed.The dynamic response are the largest at the tunnel portal,as the distance from the portal increases,it tends to decrease gradually and tends to be consistent with the tunnel body.In the range of 0⁵0m,the reduction is larger;In the range of 50⁹5m,the reduction is smaller.The key anti-seismic parts of the tunnel should be within 50m.?3?Under horizontal and transverse seismic action,The maximum relative displacement value and the acceleration are 9.06mm and 3.626m/s² at the vault.The maximum internal force of tunnel appears along the X direction of seismic action,and the maximum axial force is 385.1 kN.The stress concentration phenomenon occurs at the foot of the tunnel and waist,it were the weak parts of the earthquake resistance.The maximum principal stress is 4.34MPa,tensile stress.The minimum principal stress is negative 3.56 MPa,compressive stress.According to the ultimate strength of C25 concrete,many concrete on the secondary lining have tensile failure,they all meets the compressive requirements.?4?In this paper,a large number of tunnel damping studies are summarized.when the shock absorption layer is set for the tunnel model,the influence of the shock absorption position,material and thickness were analyzed and compared.The shock absorption layer can reduce seismic response of the tunnel structure to different extents.However,the displacement and acceleration are not reduce much,the stress and force are reduce obviously.The 20cm thick rubber shock absorption layer,setting between the primary support and the secondary lining,can reduce greatly the dynamic response of the tunnel structure,the maximum principal stress is 2.06 MPa,the minimum principal stress is negative 1.99 MPa.Compared with no shock absorption layer,the stress reduction is about 42%⁷0%.?5?For the research object of this paper,it is meeting the requirements of the structure under rare earthquakes that set 20cm thick rubber shock absorption layer between the primary support and the secondary lining.