1998 Fiscal Year Final Research Report Summary
Visualization of Seepage Failure of Sols by X-ray TV System
| Project/Area Number |
09650549
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geotechnical engineering
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
SEKIGUCHI Hideo Kyoto University, DPRI, Professor, 防災研究所, 教授 (20027296)
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| Co-Investigator(Kenkyū-buntansha) |
KOBAYASHI Shun-ichi Kyoto University, Eng., Research Associate, 工学研究科, 助手 (10243065)
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| Project Period (FY) |
1997 – 1998
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| Keywords | X-ray TV / Mechanics of granular media / Seepage failure / Boiling / Liquefaction / Image processing |
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| Research Abstract |
The purpose of this study was to make use of X-ray TV visualization techniques for investigating the process of seepage failure in cohesionless soils. A range of seepage tests were performed on homogeneous deposits of sand, on gap-graded granular media and on layered granular materials having a marked contrast in their grain sizes. The principal results obtained may be summarized as follows.
1. Homogeneous deposits of sand under conditions of gradually intensified, upward seepage flow underwent boiling at critical hydraulic gradients conforming to Terzaghi's formula, however X-ray images clearly indicated that the boiling failure was of a progressive nature and was in fact preceded by marked local deformations in the soil mass.
2. In gap-graded granular media, piping was observed to occur in such a way that finer particles were washed away through the void spaces of coarser particles, yet leaving only insignificant deformation in the granular skeleton.
3. The seepage failure that occurred in a two-layer system with a gravel layer resting on a sand layer, deserves special attention. The failure started in the form of localized liquefaction zones in the sand layer. When a liquefaction front extended to reach the overlying gravel layer, groups of gravel particles came off and successively penetrated deep into the liquefied sand zones. Notably, the upper part of the liquefied sand rose up through the void spaces of the gravel layer. The final form of failure of the entire system was violent boiling, accompanied by complete collapse of the ravel layer.
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