Study On Dynamic Response Law Of Cross-fault Tunnel Structure And New Anti-Seismic Absorption Measures Under Earthquake

China is located between the Pacific Rim seismic belt and the Eurasian seismic belt,earthquakes are frequent,with the extension of China’s traffic road network to the western mountainous areas,it is inevitable to encounter bad geology such as fault fracture zone during tunnel construction.The seismic load of the fault fracture zone often causes the tunnel structure to cause disasters such as lining cracking and misplacement,especially the seismic dynamic response law of the cross-double fault tunnel structure is more complicated,and the structural disaster is more serious.Therefore,it is of great significance to carry out the research on the seismic dynamic response law and anti-seismic absorption measures of tunnels crossing single(double)fault fracture zone.Based on the Shantou Bay Tunnel,a key project of the Shantou Railway,this thesis studies the dynamic response law of the tunnel structure across single(double)fault fracture zone under seismic load,and the anti-seismic performance of new anti-seismic measures for cross-double fault tunnel structure under seismic loading,and puts forward engineering suggestions for the seismic fortification of Shantou Bay Tunnel,and the main research results are as follows:(1)Based on the finite difference fraction value simulation method,the numerical calculation of seismic dynamic response of tunnel structure across fault fracture zone is carried out,and the seismic dynamic response law is revealed.The results showed that:The seismic dynamic response of tunnel structure abruptly changes within the range of 20 m on the fault fracture zone and the left and right sides,and the acceleration response is different at different positions of the ring section,among which the acceleration value is the largest at the vault,which is 2.30 times the acceleration value of the non-fault area lining structure;The stress at the arch waist is concentrated,and typical tensile shear failure occurs,in which the maximum principal stress and maximum shear stress are 7.89 MPa and 25.62 MPa,respectively.(2)A calculation model of cross-fault tunnel is established,and the influence of different factors such as fault width,inclination angle and P-wave incidence angle on the seismic dynamic response of tunnel structure is analyzed.The results showed that:Under seismic loading,the acceleration response of tunnel structure increases with the increase of fault width;The acceleration response of the tunnel structure gradually increases with the decrease of the fault inclination,and when the fault inclination angle is 30°,the acceleration response value reaches the maximum,which is 5.7times that of the input acceleration wave;The acceleration response of the tunnel structure decreases with the increase of the incidence angle of the P wave,and the acceleration response reaches a maximum of 8.52 m/s~2when the P wave is incident at0°.(3)A calculation model of cross-double fault tunnel is established,and the influence of different factors such as fault spacing and P-wave incidence angle on the seismic dynamic response of tunnel structure is analyzed.The results showed that:The fault fracture zone amplifies the dynamic response of the tunnel structure,and the larger the fault fracture belt width,the more significant the dynamic response of the tunnel structure;The displacement response of the cross-double-fault tunnel structure is different from that of the cross-single-fault tunnel structure,and the vertical displacement of the tunnel structure between the two faults shows an obvious"amplification"phenomenon,and the lateral displacement change is small.(4)A numerical simulation model of the new anti-shock absorption measures was established,and the anti-vibration absorption mechanism and effect of the new anti-shock absorption measures were analyzed.The results showed that:The"shock absorbing layer+flexible articulation"structure is set in the fault fracture zone and both sides,which effectively reduces the dynamic response of the tunnel structure,and the dynamic response of the tunnel structure gradually decreases with the decrease of the spacing between the flexible articulated segments of the lining structure.When the spacing of flexibly articulated segments was 6 m,9 m and 12 m,respectively,the stress response reduction rate exceeded 11%.Considering the difficulty of construction,economic cost,length of trolley,etc.,it is recommended that the spacing of the new flexible articulated structure be 9 m.(5)The structural model test of double-fault staggered tunnel was carried out,and the anti-staggering performance of the anti-vibration absorption measure of"shock absorbing layer+flexible articulation"was analyzed.The results showed that:Under the condition of fault displacement of 20 mm,the maximum displacement of the tunnel structure spanning 150 m fault spacing occurs at the interface between the fault and the surrounding rock.The new anti-vibration measures improve the vandal resistance of the tunnel structure by improving the deformation ability of the tunnel lining.