Abstract: Landslides in the existing soil and rock debris slopes are one of the major hazards in highway projects. In this paper, the subsurface hydrological and geological conditions of the landslide were introduced in details on a debris landslide at an expressway between station K121+100 and +330. The slip surface was determined from the site monitoring data. The main evaluation results are: 1) the slip surface of the landslide was able to be determined from the site monitoring data. The accurate determination of the slip surface from the monitored data is essential to the landslide mitigation construction and the safe operation of the highway. 2) The landslide was evaluated with the transfer coefficient method under two extreme loading conditions. It is concluded that the heavy precipitation was the major factor that contributed to the slope failure.

Key words: Debris Landslide, Inclinometers, Deformation Monitoring, Transfer Coefficient Method