1993 Fiscal Year Final Research Report Summary
| Project/Area Number |
04650432
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
基礎・土質工学
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
TAKEMURA Jiro Tokyo Institute of Technology, Associate Professor, 工学部, 助教授 (40179669)
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| Co-Investigator(Kenkyū-buntansha) |
OKAMURA Mitsu Tokyo Institute of Technology, Reseach Associate, 工学部, 助手 (50251624)
HIROOKA Akihiko Tokyo Institute of Technology, Research Associate, 工学部, 助手 (70238400)
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| Project Period (FY) |
1992 – 1993
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| Keywords | Two layred ground / Sand / Clay / Bearing capacity / Deformation / Centrifuge model test |
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| Research Abstract |
Centrifuge model tests were carried out to investigate bearing capacities and deformations of two layred soil in whicha sand oelies a relatively soft clay. Non-dimensional parameters which might directy influence on these phenomena were derived from dimensional analysis. Centrifuge tests were divided into two series. One is bearing capacity tests which were conducted under constant loading rate by using strip and circular footing, and the other is consolidation tests in which model grounds were subjected to a constant load less than its bearing capacity through a circular footing. All test were conducted under 100g and constant thickness of clay laer varying with ratios of the thickness of sand to the footing width, H/B.Following conclusions are derived from this study.
(1) Normalized bearing capacity, 2qf/ gammaB, is found to be a function of H/B, and pO/ gammaB, where gamma is effective unit weight, cu the undrained shear strength f underlying clay, cu/ gamma B normalized bearing capacity of clay and pO/gB normalized overburden resssure. The 2qf/ gammaB increases linearly with cu/ gammaB and pO/ gammaB under constant H/B.
(2) The bearing capacity of the two layred soil increases with H/B until it becomes the bearing capacity of the uniform infinite sand layr. The value of H/B over which the bearing capacity is constant in that of the infinite sand, (H/B)**, is about 1.5 to 2 for circular footing and 4 for strip footing.
(3) Failure mechanisms of the two layred soil can be classified into two categories ; one is general faiure in sand layr which occurred for (H/B)** and the other is punching failure forming a block of sand beneath the footing for H/B smaller than (H/B)**.
(4) Consolidation of the two layred soil under constant load increases with its intensity. A single uique relationship was found between the ratios of applied load intensities to beaing capacities and consolidation settlements in the grounds with H/B of 1.0 to 2.0.
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