粒子系の混合と間ゲキの量および性質について

客土に関する基礎的研究 (II)

抄録

The present study developed from the former study on sand or other materials consisting of grains of uniform size or of relatively limited size range. Real soils were used this time, to test how porosity and pore size change after particle mixing.
Porosity, which represents the quantitative characters of pores, changes with the disposition of soil granules and primary grains not forming granules, with the disposition of primary grains within granules, and with the breaking process of granules. This is differnt from the case of sand or uniform grains.
The changes of porosity were classified into three types. In type I, porosity approaches that of dressed soil, without being lower than that of original soil. In type II, porosity approaches that of dressed soil, without surpassing that of original soil. Both cases were observed when the difference of porosity of the two materials was above 10%, owing to the existence of granules, aggregates or other secondary grains giving high percentage of apparent pores and, consequently, high porosity, because of the materials being real soils. Type III is the case when optimum mixing ratio (20-30%) is attained by mixing with soils with higher percentage of fine grained fraction. The existence of such a case is easily expected from the previous report. In some cases the errors of porosity measurement might be involved, and the optimum mixing ratio was conspicuous if the soils were thoroughly tamped. The qualitative change of pores was confirmed by pF measurement and was conspicuous particularly at low suction pressure. This was also indicated by the change of mean pF value.
The principle by Childs and others for obtaining permeability coefficient by conbiming capillary models was applied to the changes of pores and permeation, and an index of the effect of pore distribution on permeability coefficient, represented by X in the formula K=MX was computed. It was indicated that the factor responsible for the seepage control effect of mixing was the qualitative change of pores at low suction pressure (below 30cm). Stress was placed on the necessity of comparing permeation in saturated condition when discussing seepage control effects.