Model test on mechanical characteristics of shallow tunnel excavation failure in gully topography

•Tunnel excavation failure process was observed through model test.•The variation law of surrounding rock stress and displacement caused by tunnel excavation in gully area was presented.•The factors of tunnel excavation direction and slope angle were considered in the model. The collapse failure occurs occasionally during the construction process of a shallow tunnel in gully terrain. This study aimed to investigate the relationship between the collapse failure of loess tunnel construction and the longitudinal terrain, and further explore the influence of slope angle and excavation direction in this terrain. A model test considering the gully topography was constructed to measure the surrounding rock pressure and deformation under different working conditions. It was found that the surrounding rock stress and displacement had significantly longitudinal effect along the tunnel, and model collapse failure presented at the slope position. As the slope angle increased, the stress and displacement of the surrounding rock at each monitoring section gradually increases. The excavation direction, especially the towards-slope excavation, had more disturbance to the tunnel surrounding rock than slope angle. This demonstrates the potential for general applicability to guide the design and construction of a shallow tunnel and avoid the collapse failure.