| Tunnel earthquake damage is one of the common important disasters in tunnel engineering.Under the action of earthquake,the tunnel will have concrete blockage,dislocation and other earthquake damage,which will seriously endanger the safety of the tunnel lining structure,especially at the fault and broken zone.The tunnel earthquake damage phenomenon has increased significantly.At present,there is little research on the seismic dynamic response law of the surrounding rock lining structure of the fault tunnel.A correct understanding of the dynamic response law of the structure is the basis for reducing and controlling the seismic damage of the tunnel and ensuring the safety of the structural performance.This paper uses a combination of theoretical derivation and numerical simulation to study the influence of different fault widths,inclination angles and surrounding rock properties on the dynamic response of the structure.On this basis,the seismic countermeasures are studied,and some research conclusions are obtained:(1)Based on the collected tunnel earthquake damage cases,statistical analysis is carried out from the aspects of earthquake damage characteristics,earthquake damage location,earthquake damage occurrence mechanism,etc.,and the distribution characteristics of the tunnel earthquake damage and the seismic response law of the lining structure are obtained.Studies have shown that the occurrence probability of tunnel earthquake damages from high to low is lining cracking,tunnel entrance and slope collapse,lining spalling,etc.The lack of compactness between the primary lining and surrounding rock will seriously reduce the seismic capacity of the tunnel.(2)Based on the numerical analysis software FLAC3 D,a calculation model of the fault tunnel surrounding rock-lining structure was constructed.After three-dimensional seismic stress loading,the response laws of structural acceleration,displacement,stress and plastic zone under different fault widths and dip angles were obtained.It is verified by comparison with the seismic damage data of the tunnel at the earthquake site.(3)Based on the response displacement method,the internal force displacement change formula of the tunnel when a long tunnel crosses a fault under the action of an earthquake is deduced,which reveals the stress and displacement transfer change law inside the structure,especially the interface between the fault and the surrounding rock,and derives the fault activation criterion.The case verification of Longxi Tunnel Project has good rationality and effectiveness.(4)In order to study the interaction law between surrounding rock and lining structure,the numerical calculation of the seismic dynamic response of the surrounding rock and lining structure of the fault tunnel under different surrounding rock properties was carried out,and the changes of the tunnel lining structure displacement,internal force and plastic zone with the surrounding rock properties were obtained..Studies have shown that the better the quality of the surrounding rock,the more beneficial it is to the lining structure,but it will aggravate the damage to the lining structure at the interface between the fault and the surrounding rock.(5)In order to propose anti-seismic measures with practical engineering value,the dynamic response of the surrounding rock-lining structure of the fault tunnel under different damping layer thicknesses and different grouting layer thicknesses was studied,and the internal force,displacement,plastic zone,etc.of the structure after the anti-seismic measures were set dynamic response law.Research shows that the combination of shock-absorbing layer in the surrounding rock of the ordinary section and the combination of shock-absorbing layer in the surrounding rock of the fault section and local grouting reinforcement can effectively reduce the internal force and displacement of the structure,and provide a basis for the selection of reasonable seismic measures for tunnel engineering.The paper has 84 pictures,10 tables,and 118 references. |
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