Seismic Response Analysis Of A Highway Tunnel Crossing Fault Fracture Zone In High Intensity Area

Mountain highway tunnel in high intensity region will be damaged seriously in earthquake,especially when it cuts across fault fracture zone.Tunnel lining in fault fracture zone will crack,shear failure and even collapse in earthquake.These study of tunnels of seismic and shock absorption is the key points and difficulties in construction of tunnel engineering,to research through the fault fracture zone seismic response law of mountain tunnel is helpful to pass through the fault fracture zone tunnel seismic and shock absorption research foundation,in order achieving to improve the purpose of the seismic capacity of the tunnel cutting across the fault fracture zone.In this paper,the research is based on Qipanshi tunnel engineering examples,studied the seismic response laws of the tunnel cutting across the fault fracture zone in directions of inputting the different seismic accelerations,found the most unfavorable position in the process of tunnel seismic and analyzed the safety of tunnel lining monitoring points.Specific contents include:(1)The technical route of the paper was determined by consulting data and reading literatures.The contact model and constitutive model for modeling were determined by learning from relevant researches on fault movement mechanism and dynamic principle of seismic response,and the parameters were determined by consulting data and calculation.(2)It's determined that the seismic intensity of the tunnel site is ? degrees according to the seismic data of the tunnel site,and Then using SeismoSignal software,the Wenchuan wave is intercepted,attenuated,band-pass filtering and baseline correction.Finally,the seismic acceleration corresponding to the actual situation of the tunnel site is generated.(3)Using the finite element software to model and calculate the tunnel of cutting across the fault fracture zone,and the response laws of acceleration,relative displacement,internal force and stress of tunnel lining are analyzed in the case of seismic waves inputting along the tunnel transverse,longitudinal,vertical and three directions of waves inputting at the same time.The conclusion is:(1)The acceleration response of tunnel lining in the fault fracture zone produced obvious amplification effect,when the seismic acceleration inputs along the tunnel transverse,longitudinal and vertical the response of lining accelerations in the fault fracture zone was respectively amplified by 8.66%,13.83% and 27.83%;(2)The displacement of tunnel lining shows that the worse the surrounding rock is,the bigger the relative displacement will be,and the relative displacement of the deep buried lining is smaller than that of the shallow buried lining;(3)The maximum axial force and shearing force of tunnel lining are almost at the position of arch foot and foot of wall of the fault interface.The maximum bending moment occurred at the foot of wall of the middle fault fracture zone.Stress concentration occurs in tunnel lining at the fault interface,and the maximum stress occurs at the arch foot and foot of wall of the fault interface.(4)After the safety analysis of the tunnel,the conclusion is: When using the safety factor method,33 of 96 monitoring points of the tunnel lining fail to meet the safety factor requirements of the eccentric compression member in the code,which is a compression member with large eccentricity that is prone to cracking and failure.Among them,30 points are located in the lining vault,inflected arch and foot of wall in the fault fracture zone.