| With the "One Belt and One Road" and the pace of transportation power strategy,China's transportation industry is in a period of vigorous development.With the expansion of the transportation network to the west,many lines pass through the high intensity mountainous areas in the west,and often face the problem of tunnel landslide.These areas have complex topographic and geological conditions.The mutual feeding mechanism of seismic wave propagation and spatial dynamic coupling effect of tunnel underpass landslide under seismic action are not clear,which brings great challenges to tunnel construction and operation.Tunnel-landslide system interaction caused by earthquake induced landslide revival has become a core scientific problem to be solved urgently.The potential seismic action and the limitation of topography and geology condition,Sichuan Tibet railway,Xining-Chengdu High-speed Railway,Chu-da expressway in Yunnan,Renmu Xin Expressway in Sichuan,Weihe-Wudu Expressway in Gansu,Baoji-Lanzhou High-speed Railway,Lanzhou-Xinjiang High-speed Railway and Wuguan Expressway tank brook tunnel engineering in the construction and operation is faced with many of the world's rare engineering disease problem.Based on the phenomenon of "stuck neck" in the field of engineering construction under extremely complex conditions in China,this paper adopts the methods of typical engineering case investigation,shaking table test,numerical calculation and theoretical calculation.Seismic wave propagation law and spatial deformation characteristics of tunnel underpass landslide system,structural damage evaluation method of spatial dynamic coupling system,theoretical analysis of load and deformation of lining structure and safe underpass distance,seismic mitigation and isolation technology of lining and seismic prevention and control structure design are studied.The following results have been achieved:(1)The typical mode division rules and generalized model of "tunnel-landslide system" based on engineering geological analysis principle are established.The statistical analysis of nearly 100 cases of tunnel-landslide engineering shows that the slope structure is the decisive background factor of the occurrence of disasters.Seismic action,atmospheric rainfall,tunnel excavation and groundwater action are the key external inducing factors controlling the occurrence of tunnel and landslide.The spatial position of tunnel and landslide dominates the type and scale of the disease.The relative position of tunnel and sliding surface determines the interaction mode and deformation characteristics of landslide and tunnel.A total of 9 basic slope structure types in five categories were considered as the key disaster background factors.According to the number of sliding surfaces,the relative position of tunnel and sliding surface,and the action area of tunnel and sliding zone,four typical models of tunnel across the hauling sliding surface,tunnel across the main sliding surface,tunnel underpasses the hauling sliding surface and tunnel underpasses the main sliding surface are abstracted from several engineering cases with common relations.They serve as the basis for subsequent shaking table test,numerical calculation and theoretical analysis.(2)The instability mechanism and disaster mode of tunnel underpass landslide system under seismic action are revealed.Through shaking table test and numerical calculation,it is found that the lining vault and invert bear most of the seismic load due to the dual effect of seismic action and landslide deformation.The tunnel is prone to collapse and collapse of inverted arch.Under seismic action,the spatial position relationship between tunnel and landslide dominates the failure mode of tunnel lining structure,but does not directly dominate the failure mode of landslide.The four typical modes of tunnel underpass landslide system show the instability mode of "rear edge settlement extrusion,middle sliding pull,front edge shearing bulge,shallow surface of accumulation body sliding along the newly formed transfixed structural plane,the whole has a sliding trend along the sliding plane of basement fracture zone".(3)The damage evaluation methods of the lining structure of the space dynamic coupling system of the tunnel under the landslide system are proposed.The structural dynamic response evaluation is introduced based on the Arias intensity(Ia),a parameter index that characterizes the ground motion intensity.The evaluation index MIa of Ia dynamic damage amplification effect based on energy effect is proposed.The prediction model based on the elastoplastic effect is more easily obtained from the measured data,and the plastic effect of the lining structure is fully considered.Through the analysis of MIa and PEC values,the seismic failure stage and local deformation failure area of tunnel lining can be identified,which can be used as an effective early warning and prediction model.Correlation of structural dynamic damage levels based on log-normal distribution of spectral amplitudes,The correlation coefficients in statistics are used to describe the correlation between amplitudes and frequency variables.According to the correlation degree between the amplitude and frequency of different signal attributes,using the sensitivity of diversified data signals with different attributes can provide new ideas and methods for the selection of earthquake monitoring and early warning test components.(4)The design and calculation method of the typical mode of tunnel penetrating landslide system under seismic action is established.Based on the transfer coefficient method of classical mechanics and considering the instantaneous acceleration effect of seismic force,the landslide thrust calculation formula is derived based on the additional load of horizontal earthquake.Considering the dynamic interaction between tunnel and surrounding rock,a substructure-reaction displacement calculation method based on LSRDI effect is derived.The superposition of the two uses the Cerruti method on the elastic semi-infinite space to calculate the additional load generated by the tunnel lining vault.Combined with the analytical analysis of classical soil mechanics theory,the theoretical solutions of load and deformation of tunnel structure in typical modes of "tunnel across the sliding surface,tunnel underpasses the sliding surface and tunnel across sliding body" are obtained.By inverse calculation of safe buried depth and combining with the range of loose circle determined by slip line theory,a calculation method of the minimum safe undercrossing distance of tunnels in high seismic zone is proposed.(5)The technology for comprehensive prevention and control of underpasses the sliding surface under seismic action is constructed.Through shaking table test,two earthquake sequences of "foreshock-main shock type" and "main shock-aftershock type" are designed.In the typical mode of tunnel underpass landslide,the seismic damping measures of tunnel lining itself are mainly taken.An accurate design method of tunnel lining seismic isolation structure based on dynamic stiffness matching basis is proposed.The optimization structure of tunnel lining shock absorption layer based on the principle of stiffness matching is developed.The transition cushion layer and shock absorption layer are set to improve the stiffness mismatch between tunnel lining and bedrock under earthquake action.Tunnel cross sliding surface model to anchor more typical circular pile its aseismatic measures is given priority to,by setting the anchor head shock absorption measures,forming a new type energy dissipation combined anchor more round pile reinforcement technology,reduce the earthquake load transfer to the lining structure,enhance the anchor round pile's ability to adapt to seismic action,thereby indirectly protect the lining structure.The research results can provide theoretical basis for failure mode prediction and engineering safety evaluation of tunnel-landslide system in high seismic area. |
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