Sinking of Hill Road and Gravitational Deformation, a Study in South Asia and Experience for Vietnam

A steep hill slope composed of bedrock often deforms slowly but steadily by the action of gravity due to its heavy weight of bedrock slope. This is called “gravitational deformation”. On the other hand, in the Himalayas and other hilly regions in India, road administrators have suffered from sinking of hill roads for long years at many sections on steep hill slopes. According to the steep gradient of the sinking section, normal landslides with landslide clay on slip surface are not responsible for the sinking. Through a technical cooperation project in India funded by JICA, we confirmed relation between sinking of hill roads and gravitational deformation.