In this study, focusing on the quantitative evaluation of the mechanical behavior of kaolin clay at the micro scale, the deformation behavior and strength in the micro region were examined. Furthermore, the strength of the microscopic area obtained from the indent test was compared with the strength obtained from the unconfined compression test.
From the creep test results based on load control, it was found that the deformation characteristics differed at a certain water content in a microscopic region. It was also found that the liquid state of clay can be judged by this test. From the cycle indentation tests based on displacement control, it was found that the hardness differs in strength characteristics at a certain water content in a microscopic region. The displacement control test in the micro region showed that the liquid state of clay can be evaluated from the viewpoint of strength evaluation. As a result of examining the effect of the loading rate on the strength, the obtained strength was almost constant for the loading rate from 0.05 to 0.5 mm/s, and it is considered that there is no effect on strength due to loading rate. Compared with the undrained shear strength obtained by the unconfined compression test, the strength derived by micro-indenter was almost the same. In particular, it is considered possible to evaluate the strength in a microscopic region by using a rate in the range of 0.2 to 0.5 mm/s.
In this work, to evaluate the deformation characteristics of Hachirogata clay, soil tests such as one dimensional consolidation test and so on were conducted. Although this Hachirogata clay sample contained much sand and less clay from the grain size test result, it was found that the sample has high liquid limit, plasticity index, and natural water content. About the derived parameters from the consolidation test, the coefficient of volume compressibility, the coefficient of consolidation, and the coefficient of permeability were in the range of 10−4–10−2 m2/kN, 5–100 cm2/d and 10−9–10−7 cm/s, respectively. Compared with other clay samples, Hachirogata clay had low consolidation rate and permeability and high volume compressibility. Furthermore, as a result of analyzing the secondary consolidation behavior in which the strain progresses under a constant load, it was found that Hachirogata clay has high secondary consolidation rate. In addition, assuming the virtual ground composed of Hachirogata clay, the theoretical curve, and the settlement curve considering the secondary consolidation deformation amount were evaluated when the embankment load corresponding to the earth pressure was loaded on this virtual ground. The soil constant required for the calculation was the constant obtained from this consolidation test. It was clarified that it takes a long time to complete primary consolidation, and that the settlement increases when secondary consolidation starts early.
From the above results, it was confirmed that consolidation deformation of Hachirogata clay takes a long time, the amount of deformation increases, and the deformation continues over time after the main deformation is completed.
In this study, the influence of the size of the ditrigonal hole and location of Na＋ ions on the ionic conductivity of Ge-substituted Na-taeniolites (NaMg2LiSi4−xGexO10F2, with x＝0, 1, 2, 3 and 4, i.e., Ge-NTA with x＝0–4) was investigated. The lattice constant b and basal spacing c·sinβ of Ge-NTA with x＝0–3 increased with increase in the Ge content and their b and c·sin β exhibited a linear relationship. However, the b and c·sin β of Ge-NTA with x＝4 deviated from a linear relationship because the structural deformation of Ge-NTA with x＝4 was considerably larger than that of Ge-NTA with x＝0–3. Moreover, with increase in the Ge content, the size of the ditrigonal hole of Ge-NTA decreased; however, the lattice constant b of Ge-NTA with x＝0–3 increased. In Ge-NTA with x＝0–3, three types of Na＋ ions exist. They are hydrated Na＋ ions in the interlayer, dehydrated Na＋ ions surrounded by basal oxygens, and Na＋ ions drawn into the ditrigonal hole. Because the size of the ditrigonal hole in Ge-NTA became smaller with increase in the Ge content, the dehydrated Na＋ ions surrounded by the basal oxygens increased and bonding between the Na＋ ions and basal oxygens became stronger. In Ge-NTA with x＝4, the Na＋ ions coordinated with three basal oxygens and the F− ion appeared to be considerably restricted inside the ditrigonal hole. The ionic conductivity of Ge-NTA was measured from 400 to 600°C using the alternating current four-probe method. The ionic conductivity of Ge-NTA decreased with increase in the Ge content because for Ge-NTA with x＝0–3, bonding between the Na＋ ions and basal oxygens became stronger with increase in the Ge content and for Ge-NTA with x＝4, the Na＋ ions that were considerably restricted inside the ditrigonal hole hardly contributed to the ionic conductivity.