ABSTRACT:

Mikabu Belt in Shikoku Region of Japan is a geological series of green rock, where a number of large-scale landslides are in an active state. Slip layer soils of the landslides in this belt mostly consist of weathered green rock, which sometimes is also known as green tuff. Being in a weathered state, the slip layer soils contain weak clay minerals like chlorite and smectite that lower the strength of any soil. With the objective to study the influence pattern of expansive chlorite on the strength of the weathered green rock, strength tests such as triaxial and ring shear tests along with x-ray diffraction test for clay mineral analysis were carried out on the slip layer soil samples from five different landslide sites in this belt. Test results revealed that all the samples contained chlorite as the main clay mineral that partly behaved like smectite, and the strength of the slip layer soils in both effective as well as residual conditions is low.

INTRODUCTION

Japan being a mountainous country has a large number of large-scale landslides throughout the country. Active movement of such landslides at a number of places in the country has been creating various problems in engineering as well as environmental works. For example, the problems like damages to roads and bridges, houses and public facilities, and agricultural fields, breakage of electricity and water supply lines; damming up of a river or stream, etc. directly affect the human life settled near an active landslide area. These problems insist many Japanese researchers carry out various studies on landslide mechanism, its stability, and the development of countermeasure works. This paper consists of one such study, which specifically elucidates the influence of weak clay minerals on the strength of slip layer soils of landslides in Mikabu Belt of Japan.

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