@inproceedings{oai:nagoya.repo.nii.ac.jp:02003768,
 author = {ASAOKA, Akira},
 book = {Proceeding of the twelfth Asian regional conference on soil mechanics and geotechnical engineering (12ARC) : Singapore 4-8 August 2003},
 month = {Apr},
 note = {Naturally deposited clays/sands are mostly found in structured, and usually also in overconsolidated states. Furthermore, they exhibit what is more or less a condition of anisotropy. In order to describe the mechanical behavior of these natural soils, this study models super/subloading yield surfaces together with rotational hardening using the modified Cam-Clay model. Three evolution laws are introduced naturally into the constitutive laws of soils; the first one describes decay/collapse of soil structure, the second loss of overconsolidation, and the third evolution of anisotropy. Although all of these proceed with ongoing plastic deformation, it is newly emphasized that the decay of structure tends to promote plastic volume compression while the loss of overconsolidation leads to plastic volume expansion. Clay is clearly distinguished from sand by the difference in the rates of these evolution laws. As highly structured overconsolidated clay reverts to the normally consolidated state, it initially retains its structure. Then the clay begins to lose its structure very gradually with ongoing plastic deformation, during which process secondary consolidation and/or delayed compression is observed. In contrast, sand loses its structure very rapidly, not in the manner of a decay, but rather in a sudden collapse, while remaining in its overconsolidated state. The loss of overconsolidation for sand requires a huge amount of plastic deformation. Fundamental constitutive model responses of natural clay are illustrated through numerical simulations of secondary consolidation and/or delayed compression, during which softening is clearly observed with the occurrence of plastic volume compression. For sand, typical model responses are illustrated through numerical simulations of compaction of a loose sand deposit. Repeated application of low-level shear stress upon the loose sand leads to a huge amount of volume compression, which is due to the rapid collapse of the initial soil structure. Repetition of the loading also results in a rapid increase of the overconsolidation ratio.},
 pages = {1157--1195},
 publisher = {World Scientific},
 title = {Consolidation of Clay and Compaction of Sand : An elasto-plastic description},
 volume = {2},
 year = {2004}
}