| When a tunnel goes through a landslide mass,slope stability decreases and its vault is vulnerable to collapse due to construction disturbance,thus severely affecting tunnel and slope safety.At present,only a few studies about the specific effects exerted by landslide thrust on tunnel under the tunnel-landslide parallel system have been conducted.Therefore,based on the Chen Jiapo Tunnel Exit Slope Project,this thesis focused on the deformation mechanism of tunnel under the tunnel-landslide parallel system by field study,theoretical analysis,numerical simulation,etc.To start with,a differential equation about beam deflection of tunnel lining structure under the influence of landslide thrust was set up on the basis of theories of foundation beam and structural mechanics.Out of safety concern,soil compression exerted by landslide mass under landslide thrust was ignored.Formulas about bending moment,shear force and axial force of the cross section of the tunnel at the intersection were acquired through the conditions of displacement continuity and force balance at the intersection between the tunnel and the sliding surface.Definition of new parameters and analysis of the patterns of how their change affected deformation at the intersection between the tunnel,that is,when the equation k=βl varied from zero to one third with the landslide thrust on the tunnel considered to be a certain value,the larger the k value was,the smaller the absolute value of bending at intersection was and the bigger the absolute value of shear.In the second place,based on the transfer coefficient method and hypothesis of triangle-shaped distributed load of landslide thrust,thrust exerted by the slope on tunnel lining structure was inferred.Besides,from Chen Jiapo Tunnel Exit Slope Project,distributed load forces exerted by the tunnel horizontally and longitudinally were respectively calculated as follows: qz= 436.1 kN/m,qx= 208.9 kN/m。In addition,theoretical calculations and numerical simulation calculations of the data from the case project of Chen Jiapo Tunnel Exit Slope showed that though its slope deformation was restricted,the tunnel itself was under great landslide thrust.When the reduction coefficient was 1.4,the horizontal displacement of the slope increased dramatically and the slope became unstable.The greater the reduction coefficient was,the more unstable the slope was and the greater the landslide thrust exerted on the tunnel lining structure was.When the slope slid,structural damage may happen to the tunnel because of too much landslide thrust exerted on it.Given that the intersection between the tunnel and the slope was the origin of coordinates,the effect of landslide thrust on the tunnel would vary from-l to l,with l being the length of the tunnel located in the landslide mass.At last,according to the calculation formula inferred through the theories adopted in this thesis and relevant research conclusions,methods about how to figure out longitudinal bending moment design,shear design and axial force design of the tunnel in the tunnellandslide parallel system were put forward.The concluded flow chart displaying how to design the longitudinal structure might give reference to the longitudinal design of tunnels in similar projects. |
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