報告書番号

U87080

タイトル（和文）

砂礫地盤への貫入試験の適用法の提案

タイトル（英文）

A proposal on application of penetration tests on Gravelly Soils.

概要 （図表や脚注は「報告書全文」に掲載しております）

原子力発電所の第四紀地盤立地を検討するとき、有望な地盤の一つとして洪積砂礫地盤があげられる。 洪積砂礫地盤は、通常の構造物に対しては十分な支持力を有することから、従来、詳細な調査・試験が行われていなかった。当所では原子炉建屋など、重要構造物基礎の沈下や地震時安定性の検討を行うために種々の原位置調査・試験法の開発を行っている。 本報告は、その一環として、砂地盤や粘土地盤の沈下、支持力の推定や物性値の概略評価に多用されている貫入試験の適用範囲を密な砂礫地盤にまで拡大することを目的として実施した土槽試験および現場実験の結果を述べるものである。

概要 （英文）

The diluvial gravelly ground seems to have a high possibility as a foundation ground in order to construct the nuclear power plants. Bat because diluvial gravelly grounds already have a large bearing capacity under natural condition, it is not necessary to carry out the detaled survay and tests for such grounds. The CRIEPI proceeds the development of in-situ testing methods to evaluate the settlement and stability of foundation of important sturucture against earthquake as is shown in Fig.1. In this report,the empirical formulas, which is based on the penetration tests for artificial gravelly deposits with the different distributions of grain size by using the large scale soil container, have been proporsed on the relationships between soil density or shear wave velocity and SPT blow count (N-value) for wide confining stress range. And it is clearly demonstrated that in-situ soil density and shear wave velocity are estimated by N-value by applying above proposed relationships to the field date of two site investigations. Through this study,the following conclutions are obtained. 1) The standard penetration test can be applied to gravelly soils with more reliability if the metal of the cutting shoe of the probe is hardened so as to prevent breakage by hitting hard gravel particles. 2) Empirical equations for gravelly soil deposit based on the laboratory data to estimate the relative density and shear wave velocity from N-value and effective overburden pressure are expressed as follows. Dr = 16.2 * N^0.43 / (σv')^0.1 (%) Vx = 106 * N^0.25 * (σv')^0.14 (m/s) Where σv'; effective orverburden pressure 0.5 < σv' < 6.0 (kg;cm2）These two equations are the average ones for various distribution of gravel size. 3)The correlations between N-value by STP and Nd-value by large penetration test, which seems to have better applicability for gravelly soils than SPT, has been established from laboratory test results and they are written as follows for each soil type. Nd = N/2 (for gravelly soils) Nd = N/1.5 (for sands) At the same time, the correlation between N-value and cone-tip resistance by static cone penetration test has been propose for gravelly soils in this report too. 4) In-situ real soil density and shear wave velocity obtained from two site investigations are in good agreement with those value calculated from N-values of same sites by the proposed equations. And its applicability to in-situ investigations of gravelly ground was proved.

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