Kita-Kobe District Landslide

Location

LOCATION: Miki City and Yoshikawa-Cho, Minou-Gun, Kobe City, Hyogo Prefecture.SIZE OF SLIDE:

Date of Slide

Past records indicate a large scale landslide occurred in 1879. Since 1879, several large scale landslides have occurred.

Size of Slide

Length: 300 m; Width: 120 m; Depth: 25 m; Area: 3.6x105m2; Volume: 4.0x106m3.

Damages

DAMAGES: The recent slide occurred in September, 1941, and damaged 8 residential structures.

Geology, Mechanism of Failure and Type of Movement

The site area is located along the north side of Rokko-San at an elevation between 100 to 250 m. The site is underlain by the Upper Tertiary Kobe Group. Active tectonic movement in the region uplifted Rokko-San (called the Rokko-San Uplift), resulting in the majority of the beds to dip towards the west. The site area has been subjected to severe deformation including folding, faulting and flexuring and is one of the primary causes of sliding. Geology of the site area consists of highly weathered mudstone, and fine grained tuff that shows a high level of argillization (to montmorillonite). The slide planes developed due to infiltration of rain water and ground water.

Mitigation Measures

In order to remove the ground water (the primary cause of the sliding), drainage tunnels, a drainage well and drainage borings were installed as well as the control and restraint of the continually active slide. Surface drainage control works and steel pile works have also been implemented.