Study On Failure Mode Of Shallow-buried Tunnel

With China’s rapid economic growth，a large number of tunnels and undergroundengineering have been constructed，such as the railway, highway, water resources andhydropower, national defense, city metro and so on. Especially the urban railconstruction have made a fairly large shallow buried tunnel. As a result, it’s particularlyimportant for us to do research on shallow buried tunnel research. This paper mainlytalks through the failure mode of shallow buried tunnel by doing model test study,combination with FLAC numerical simulation and associated with urban light-rail ofXiaoshizi transit tunnel. The main research contents are as follows:Shallow tunnel has been preliminary definited, and it briefly describes the failuretype of the shallow tunnel, such as local rockfall damage, the overall damage anddeliquescence expansion damage. Furthermore, Peck empirical formula, Instabilityellipsoid body model in the shallow tunnel and surrounding rock stress calculationformula involved the failure mode are analysed briefly.Model tests have been done about shallow sandy soil tunnel, and the parameters ofthe test material are got by direct shear test. In the course of model test, different failuremodes are taken by the front camera on different thickness of the tunnel. And throughthe FLAC numerical simulation, the failure modes of model test are verified. Accordingto the failure mode of shallow buried tunnel. Correction Loose pressure calculationmethod of shallow buried tunnel is deduced.The surrounding rock’s stability criterion is anslysed in the tunnel. It’s morereasonable to get the criterion by the safety factor method than the analysis ondisplacement or plastic zone only. Then, strength reduction method is adopted onshallow soil tunnel’s failure mode.Combined with the urban light-rail of Xiaoshizi transit tunnel, analysis aboutshallow buried tunnel’s failure modes is done by FLAC numerical simulation. Itincludes no supporting conditions, strength reduction method condition and supportingcondition. Analysis of surrounding rock deformation, the plastic zone, and the shearstrain incremental changes, and according to the results, suggestion is taken on thesupporting of surrounding rock.