Landslide clay behavior and countermeasures works at the fractured zone of Median Tectonic Line

Median Tectonic Line is a first class and very active fault line in Japan. Large fractured zones due to the plate movement have developed along this line. With the construction of Shikoku Jukando expressway along it, many large-scale landslides have also been occurring. Therefore, it was supposed to be very important to carry out a study on landslide behavior and landslide soil characteristics along this line so that suitable countermeasure works could be designed, and the safety of the expressway could be increased. After the study, it was found that ϕ’ of landslide clays along the fractured zone was relatively small, in a range of 20°-35°, and the drop from to ϕ’ was ϕr notably big, about 15°. This small angle of shear resistance and a big drop from ϕ’ to ϕr were supposed to be some of the reasons why landslide countermeasure works along MTL are generally difficult.