抄録
The shrinkage of allophane soil was studied in relation to structure. The structure was described in terms of two fabric units called S-unit and L-unit which were observed at different magnification levels with a scanning electron microscope. An S-unit is 1-2 μm in diameter and an L-unit is 100-200 μm in diameter. The characteristics of shrinkage and structure which were found to correspond to each other are as follows : (1) the commencement of residual shrinkage at pF 4.1 and the large amount of this shrinkage corresponds to the skeleton which is framed by a series of S-units and wherein allophane is continuously distributed. (2) the increase in normal shrinkage range after remolding corresponds to the breakdown of the structure with L-units and the subsequent release of the void water in the structure by remolding. (3) the reappearance of pF 4.1 as the value at which residual shrinkage commences after remolding corresponds to the fact that S-units remain after remolding. As for the effect of the shrinkage on the structure, it was concluded that the S-units became compacted and then combined, causing the L-units to become rigid. The structure information presented here was applied also to the description of such behavior as the decrease of liquid limit with decreasing water content and the sensitivity of allophane soil.
