First of all, testing samples were made by mixing silt and fine sand in various proportions. Then they were saturated with water in glass vessels and it was studied how the component rate of silt and the thickness of the samples affected the cracking which occurred when they were dried. Further, the study was extended to the relations between the rate of silt in the samples and the percentage of water in them in the early stages of cracking. From the test results the following facts were ascertained :
1. Shapes of the cracks which appear in the fine-grained deposit in a given vessel is affected by the component rate of silt. When the rate of silt in the sample is 30 % or more, a relation of some N=As+B (A and B are decided by the thickness of the sample) is observed between the crack density (a tentative name) and the rate of silt.
2. Shapes of the cracks are affected by the thickness of the sample. When the component rate of silt in the sample is 50 % or more, a relation of some N=A
-D (A is decided by the rate of silt) is observed between the crack density and the thickness of the sample.
3. The cracking ceases to occur if the rate of silt decreases to some degree. The area where no cracks appear varies with the thickness of each sample, but in any case none of them appear if the rate of silt is less than 10 %.
4. There exists a functional relation of some H=0.006+0.17 between the percentage of water and the component rate of silt in the sample when the first cracking starts. That is, the higher the rate of silt is, the more cracks appear under moisture conditions.
In future, the constancy of the above results is to be further confirmed through examinations of such experimental operations as the drying and the mixing of samples and through preparation of more specimens. In addition, the same tests are to be conducted with other kinds clay, their results being applied to general fine-grained deposits.
View full abstract