Testing of very soft clay

Because nearly 90% of its land being mountainous in Japan, the land necessary for industrial and agricultural expansions was built by reclamation and draining of shallow water areas since the ancient ages. Using the soil dredged from the sea bottom with a pump dredger is the most economical method, and this method has been used in most of the large scale land reclamation projects. Today, land reclamation is done not to make more land but to dispose the soil generated by dredging to open up navigational channel. In such a project, the volume of the dredged soil poured into the reclamation site becomes larger than the original volume of the sea bottom soil due to mixing of a large amount of sea water with dredged soil. Therefore, we must be able to quantify the volumetric change of soil in order to determine how much space is necessary to dispose the dredged soil. The authors conducted a series of research work to solve this problem, and this paper describes the tests that were conducted relating to very soft clays and the results of these tests.