Magnetic resonance imaging (MRI) is accepted as medical imaging technique capable of producing high quality images of the inside of the human body. MRI produces three-dimensional volume images of the internal structures using powerful magnets and radio waves, without any direct contact.
As part of a study on the engineering properties and the exploration methods of the ground, we compared the engineering properties of soil from Japan and other countries to identify if regional differences in ground properties occurred (Tanaka and Tanaka, 2004). The shear strength and the consolidation yield stress of a cohesive soil layer obtained from the seabed off Singapore during the course of this study were very large with respect to the effective overburden pressure. This indicated that the engineering properties of the cohesive soils differed significantly from those of marine cohesive soils in Japanese port areas. 14C carbon dating revealed the possibility that the layer had been affected by dry conditions caused by a fall in sea level during a glacial age. We have hence been studying the effects of drying shrinkage of soils on their engineering properties, focusing on effective residual stresses, consolidation characteristics, and overconsolidation ratios. The results of these studies show that the drying history of the ground has a considerable influence on the engineering properties of the soil. Accurate observation of changes in water contents within specimens thus became essential to the further development of our study. We therefore used MRI to make observations of changes in the water contents of soil samples during drying, and of the water absorption processes of soil samples, to clarify the relationship between changes in water content and the physical properties of the soil.
