When highway tunnels are constructed in the southwest mountainous area in China

they often have to pass through the landslides and other adverse geological disasters. Especially

the tunnel orthogonally crossing the landslide is considered as the most complicated situation. In this case

two serious conditions are coupled

i.e.

deep-seated landslide mass with a great thickness and exposed slip surface of landslide. Thus

the coupled action leads to strong interactions between landslide and tunnel

which also can induce the deformation and crack diseases of landslide and tunnel. In this study

a highway tunnel is investigated

which orthogonally crosses an old landslide with an over 60 m thickness in the southwest mountainous area. Due to the interaction of the tunnel-landslide system

the mechanism of the engineering diseases is deeply studied. The numerical analysis method is used to calculate and analyze the stress and deformations of landslide and tunnel as well. Finally

the calculated results are compared with those obtained by the recommended transfer coefficient method. The results verify that the numerical analysis method is more reasonable for analyzing the interaction between the landslide and the tunnel. Meanwhile

it is proven that the final control measures based on stress deformation control theory has obvious technical and economic advantages. At present

the tunnel has successfully passed through the landslide. As it is rare to easily manage this complex tunnel-landslide system

its design analysis method and comprehensive prevention measures provide helpful references for the similar projects in the future.