Abstract
The authors studied the influence of organic matters of volcanic ash soils on the strength.
The results obtained are summarized as follows:
1) Unconfined compression strength of soil compacted at natural water content increased remarkably to pF 3.8 with drying, but it decreased above pF 4. 4 with further drying (Fig.5). This was explained by the shrinkage with drying of aggregates due to organic matters of soil.
2) Similarly, the apparent cohesion increased with drying to pF 3.8 and decreased with further drying. But then the angle of shearing resistance monotonously increased with drying, making the degree of increase change at pF 3.8 (Fig.6).
3) The shrinkage of soil ended at a higher water content and the shrinkage ratio became smaller with increase of organic matter content of soil (Fig.8). This was explained that soils having higher organic matter content developed aggregates more. Therefore, tha unconfined compression strength decreased with increase of organic matter content of soil (Fig.7).
