1) We studied the elastic properties of the same kinds of soil taken from several sections in Tokyo as those adopted in our preceding studies. The soils were taken out in the natural state from various depths underground in Kongo, Maru-no-uti, and Komatugawa, by means of the boring processa All of specimens, which were divided into 4 classes, namely, clay, silt, silty-clay, and loam, were made into the form of a cylinder, and tested in both the natural and the recomposed states. 2) We obtained the transverse wave-velocity in these soil specimens as well as the longitudinal wave-velocity, by means of the vibration methods, and then computed their moduli of rigidity and Young's moduli from the following equations, respectively μ=ρV2l, and E=ρV2l. We calculated Poisson's ratio of these soils from the following equation The values of these constants are shown in Tables I and II. 3) We determined the normal and the tangential solid viscosities, namely γ1 and γt, from the curved portions near the origin of each reducing curve,, by means of the following equations in which the symbols have the same meaning as before. The normal solid viscosity coefficients of these soils are greater than their tangential solid viscosity coefficients, and the greater the decrease of moisture content in the soil specimen, the less difference there is between normal and tangential viscosities. The ratio of γl to γt seems to be about 2・0 in the case of diminishing the moisture content of the soil, while it approches about 1・0 when the moisture content increases. 4) The transverse wave-velocity, the modulus of rigidity, and the tangential solid viscosity coefficient, as well as the londitudinal wave-velocity, Young's modulus, and the normal solid viscosity coefficients of the soils in the natural state are greater than those obtained in the recomposed state. 5) The elastic constants, such as Young's modulus and the modulus of rigidity, decrease somewhat rapidly with the increase of moisture content. These are of the order of 107～108 (c.g.s.) at the moisture content ranges of about 50%～30% ; the solid viscosity coefficients of these soils are of the order of 104～105 (c.g.s.) ; and also the transverse wave-velocity varies from about 60 m per sec to about 250 m per sec at the above moisture content ranges. Poisson's ratio of these soils, however, increases with the increase of the moisture content ; the variation of which is 0・43～0・19 at the moisture content ranges of about 49%～32% in the case of silty-clay at Maru-no-uti ; while 0・30～0・15 at the moisture content ranges of about 48%～40% in the case of soils at Kongo. It seems to us that Poisson's ratio of loam at Kongo is smaller than that of silty-clay at Maru-no-uti within a certain moisture content limit. This difference may be chiefly due to the state of the internal structure of the soils. 6) The resonance frequencies of the second maximum amplitude attain about three times the frequency of the fundamental resonance, a fact of which was already pointed out in our preceding paper. The observed vibration of the soil specimen can be, therefore, revealed by the transverse vibration in a clamped- and free-end bar. In conclusion, our sincerest thanks are due to Dr. T. Watanabe, member of Geotechinical Committee, Government Railways of Japan, who kindly gave us the soils of Mar-no-uti and a kind of clay adopted in our experiments. We also wish to express our thanks to Dr. N. Miyabe, member of our institute, who gave us a permission to study the soil specimen of Komatugawa which was recently collected himself.

雑誌名

東京帝國大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, Tokyo Imperial University

巻

15

号

1

ページ

67 - 86

発行年

1937-03-30

ISSN

00408972

書誌レコードID

AN00029699

フォーマット

application/pdf

日本十進分類法

453

出版者

東京帝国大学地震研究所

出版者別名

Earthquake Research Institute, Tokyo Imperial University

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