Abstract
The effect of adsorbed cations on the swelling and slaking properties of clayey soils was examined, using the Na-and Ca-saturated soil blocks shrunk by drying.
The results are as follows:
1) A large difference in swelling between the non-volcanic ash soils and volcanic ash soil was recognized; that is, the swelling of volcanic ash soil was extremely low irrespective of the adsorbed cations (Figs.1, 2, 3, 4).This difference is discussed in relation to the intra-crystalline swelling of soil clay minerals (Fig. 5).
2) In comparison with the swelling of Na-soil of non-volcanic ash soils with that of the Ca-soil, the swelling of Na-soil was larger than that of the Ca-soil (Fig. 4).This difference is discussed in relation to the inter-crystalline swelling controlled by the development of the diffused double layer.
3) As a result of the swelling of three blocks which have different drying-stage, the swelling of volcanic ash soil is extremely low irrespective of the drying-stage, while in Na-soil of non-volcanic ash soils which have high swelling, two tendency is recognized;that is, the swelling of one does not inhibit following the progress of drying, and the swelling of the other does (Fig. 4).The decrease in swelling by drying, involving the low swelling properties of the volcanic ash soil, is discussed in relation to the phenomenon of irreversible aggregation of the soil particles by drying (Fig. 6).
4) The slaking types which each soil block exhibits were divided into four kinds (Photos.1, 2, 3, 4, Table 3).It was clarified that each slaking type is closely related to the swelling properties (Fig. 4, Table 3, Fig.7).
