On Shrinkage Behavior of Soil in Nakaumi Reclaimed Land

Abstract

This study investigated the shrinkage behavior of strongly clayey soil with the soil texture of LiC on SiC and the part it played in the formation of soil structure in the Nakaumi reclamation. The results obtained were as follows: 1.The strongly clayey soil in the Nakaumi reclamation, especially the muddy sediment forming the subsoil, showed the anisotropy that the shrinkage length of the vertical direction to the depositional surface of this soil changed little; the change in shrinkage length of the horizontal direction was always fairly larger than that of the vertical one in the shrinkage behavior of soil during the progress of drying. 2. It was supposed that the anisotropy in the shrinkage behavior of this soil was due to the flat faces of platelike soil particles with the low swelling being horizontally oriented and the vertical distance between the platelike soil particles, i.e., the distances between their flat faces, being shortened under the normal consolidation caused by the covering soil pressure; and consequently the horizontal ones between them, i.e., the ones between their edges, become rather larger than the vertical ones. 3. The orienting structure of this soil was also clarified by the result of an unconfined compression test. The compression stress of the vertical direction to the depositional surface of this soil was large and that of the horizontal one to it was small. 4. It was supposed that in this soil, because of the anisotropy in its shrinkage behavior, the occurrence of primary cracks was greater, the development of secondary cracks easier, and consequently the formation of the prismatic and angular blocky structure was smoother than that in the soil consisting mainly of platelike montmorillonites with a high swelling from the Hachirohgata reclamation.