Engineering Geology of Ohnaruto Bridge Foundation

Abstract

Ohnaruto Bridge, one of the Honshu Shikoku connecting bridge, is a suspension bridge of 876m center span located in Naruto Straits.
Foundation rock consists of the Cretaceous sandstone and shale which have remarkable stratifications of monoclinic structure dipping to SE at 45°-50°. Engineering propertes of the submarine foundation rock were researched by many core drillings, in-situ load tests in the holes and geophysical loggings.
Estimation for the strength of rock mass was performed mainly by the deformation modulus of in-situ load test and total point method which was attempted for the stratified rock of Ohnaruto Bridge foundation. This method is a kind of synthetic classification of rock grade evaluating characteristics of drilled core, such as hardness, shape, crack width and nature of cracks.