神戸ポートアイランドの埋立マサ土地盤の静的及び動的強度特性

概要

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A series of laboratory tests were performed on high-quality undisturbed samples of a gravelly fill made of weathered granite (locally called Masado) in order to investigate its physical and mechanical properties. The following were concluded. 1) Considering the result that the Masado fill was liquefied during the 1995 Hyogo-ken Nanbu earthquake in spite of its large particle size, some of the design codes including the methods for evaluating the liquefaction potential is hoped to be reviewed. 2) The internal friction angle ( φ_σ) of Masado fill ranges between 39.5 and 41.8 degrees, these values are relatively large compared with that of other Holocene and Pleistocene gravels having higher N i values. 3) The permeability coefficient of Masado fill ranges between 2 × 10^<-5> and 10^<-2> cm/sec, these values are almost the same as those for sandy soils. So it is reasonable to investigate the cyclic shear strength of Masado fill under undrained condition. 4) The liquefaction strength (R: cyclic stress ratio to cause DA=5% in 15 cycles) is only 0.15 to 0.23, this value is nearly equal to that of Toyoura sand with 70 % of relative density. The relationship between R and Ni value agrees well with the empirical correlation proposed by Yoshimi et al for sandy soils.
1997-08-30