Analysis of lateral slope stability during construction of a loess tunnel with a large section

For a loess tunnel with a large section passing through a lateral slope, some engineering risks like landslide or collapse are easily induced by tunneling construction, which frequently disturbs the soil mass. Based on a test section of a specific project, the lateral slope was reinforced before tunnel construction. With stability calculation for the lateral slope and using the improved strength reduction method, as well as reductions to the tensile strength index and shear strength index, the impacts of the three tunneling methods of short bench, CD, and CRD on lateralslope stability were simulated and analyzed using the FLAC3D numerical model. Engineering practice shows that the analytical results by improved strength reduction method generally agree with the actual ones under the condition of the undefined potential sliding surface of the lateral side slope, the effects on stability of the lateral slope is evident under continuous excavation, and the CRD method is most suitable for the construction of a unsymmetrical loading loess tunnel with a large section once the lateral side slope is reinforced.