Abstract:

 It is difficult to construct a tunnel in landslide area. As a result, a case study is conducted on the exit section of the Chunping No. 2 tunnel of the DaguanYongshan expressway in Yunnan, China, and the causes of landslide and the stability before treatment are analyzed according to geological conditions. Based on this, the comprehensive treatment measures for the slopetunnel oblique intersection system are proposed, and the effect of landslide treatment is analyzed by numerical simulation, so as to evaluate the safety of tunnel structure. The results show the following: (1) The slope at the portal of the tunnel has low safety under the condition of nature or rainstorm. The landslide control measures of "reverse pressure backfill + antislide pile + anchor cable" are comprehensively beneficial. (2) After backfilling treatment, the landslide body is stable in natural condition, but unstable in rainstorm condition. After treatment of antislide pile + anchor cable, the landslide body can remain stable under the rainstorm condition. (3) The pretreatment measures of pile foundation and grouting and doublelayer advance large pipe shed can ensure the safety of opencut tunnel construction. The main influence range of landslide on the tunnel exit section structure is 20 m.

Key words: tunnel portal, landslide, backfilling, comprehensive treatment, numerical simulation