1998 Fiscal Year Final Research Report Summary
Temperature dependent viscous behavior on natural clay and the extension of a elasto-thermo-viscoplastic constitutive model
| Project/Area Number |
09650546
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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 | Gifu University |
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Principal Investigator |
YASHIMA Atsushi Gifu Univ., Dept.of Civil Eng., Professor, 工学部, 教授 (90144394)
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| Co-Investigator(Kenkyū-buntansha) |
OKA Fusao Kyoto Univ., Dept.of Civil Eng., Professor, 大学院・工学研究科, 教授 (10111923)
SAWADA Kazuhide Gifu Univ., Dept.of Civil Eng., Research Associate, 工学部, 助手 (30273121)
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| Project Period (FY) |
1997 – 1998
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| Keywords | natural clay / laboratory test / temperature dependent behavior / constitutive model / micro-structure / SEM / finite element method |
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| Research Abstract |
The behavior of natural clays during one dimensional consolidation is strongly influenced by. strain rate as well as temperature. The preconsolidation pressure is a function of both strain rate and temperature. The viscous behavior of the natural clay skeleton as well as the characteristics of the permeability are discussed, based on the experimental results obtained on natural clay. Also, an elasto-thermo-viscoplastic constitutive model is developed to reproduce the one dimensional behavior of natural clays at different strain rates and temperatures. An effective stress based finite element method is applied to the experimental results of consolidation.
1) For all the tests performed, the relationship between the vertical effective stress normalized with respect to the preconsolidation pressure corresponding to the strain rate and temperature at that time, and the vertical strain is unique.
2) An elasto-thermo-viscoplastic constitutive model has been developed by extending the Adachi an
… More
d Oka's model to reproduce the behavior of natural clays at different strain rates and temperatures. The viseoplastic parameter introduced is found to depend at least as a first approximation on the temperature only through the temperature dependence of the preconsolidation pressure.
3) It is found that the proposed elasto-thermo-viscoplastic constitutive model satisfactorily reproduce the one dimensional viscous behavior of the natural Berthierville clay at different strain rates and temperatures.
An importance of yielding characteristic and an effect of the microstructure on stress-strain characteristics of Osaka Upper-Most Pleistocene marine clay are also studied. To get high quality clay samples, Pleistocene marine clays were sampled by block-sampling technique. Clay samples undertaken by the block-sampling technique are found to have higher quality than Pleistocene clay samples obtained by the tube : >sampling technique. The following conclusions are obtained from the present study : 1. Yielding properties of Osaka Pleistocene marine clays from the two sites are anisotropic. 2. The Pleistocene marine clay has a linkage structure with significant bonding, which induces more brittle behavior, higher compressive strength and higher stiffness than the disturbed and reconstituted samples. Less
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