CONTRIBUTION OF MICRO STRUCTURE TO REPEATED LOADING EFFECT ON COMPACTED ALLOPHANEOUS VOLCANIC ASH SOIL

概要

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The hardening effect and delay of propagation of pore water pressure were observed in repeated loading test on the specimens of compacted allophaneous volcanic ash soils under undrained condition. These phenomena occurred even in the specimen whose degree of saturation was higher than 95%.This research was carried out to investigate the mechanism of hardening effect of repeated loading on the above highly saturated specimens from the viewpoint on the relation between hardening effect and micro structure. Then, the following results were obtained. (1) The difference of micro structure influenced not only on the behavior of soil in the standard undrained triaxial compression test but also on that in the undrained repeated loading test. (2) Undrained repeated loading had both of hardening and softening effects. (3) The hardening effect was given by the gradual increase in contact area between soil particles, anisotropy and density resulted from deformation and fracture of soil peds and compression of residual micro air bubbles during repeated loading. (4) To obtain the yielding repeated load ratio, the strain ratio (recoverable strain/irrecoverable strain) method was more favorable for allophaneous volcanic ash soils than the strain rate method. The yielding repeated load ratio was 0.4 through all kinds of specimens used in this research.
社団法人地盤工学会の論文
1987-12-15