Abstract
It has long been difficult to differentiate the coral gravel soils when evaluating their strength because of the large variation and it has been required to resolve this issue. This has been done by means of a study focused on the drainage characteristic. As for the general soils of mainland Japan, the content of fine fraction at 50% is considered adequate for the separate point between cohesive soil and intermediate soil. However, the necessary content of the cohesive soil with “c” evaluation of coral gravel soils were found to be 70, 80, 75 and 80% for the ports of Nakagusku, Naha, Hirara, and Ishigaki. Additionally, the Plasticity Index for the same cohesive soils were found to be 35, 20, 20 and 20 for each of the four ports. Based on the research and its result in this paper and on other research in the past, the way how to differentiate the coral gravel soil that should be sandy, intermediate, or cohesive, was proposed.
