1998 Fiscal Year Final Research Report Summary
Engineering Approach to the Evaluation of Bearing Capacity of Pile Considering the Ground Crushability
| Project/Area Number |
09450182
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | KYUSHU UNIVERSITY |
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Principal Investigator |
OMINE Kiyoshi Kyushu Univ., Civil Eng., Research Associate, 工学部, 助手 (60248474)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Ken-ichi Fukuoka Univ., Civil Eng., Research Associate, 工学部, 助手 (20235336)
OHNO Shiro Kyushu Univ., Civil Eng., Research Associate, 工学部, 助手 (70274488)
YASUFUKU Noriyuki Kyushu Univ., Civil Eng., Associate Professor, 工学部, 助教授 (20166523)
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| Project Period (FY) |
1997 – 1998
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| Keywords | BEARING CAPACITY / SKIN FRICTION / END BEARING CAPACITY / PARTICLE CRUSHING / COMPRESSIBILITY / INITIAL STRESS / CALCAREOUS SAND / FAILURE MODE |
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| Research Abstract |
Crushable sandy soils can be found throughout the world and are characterized very compressible. It have engineering problems of very low bearing capacity and large settlement of the pile foundation in such grounds. In this study, in order to develop a rational geotechnical method for the evaluation of the bearing capacity of pile, it showed the mechanisms of the mobilized bearing capacity. And then the influence of the stress condition and the soil properties on the bearing capacity in sands is discussed based on the theoretical considerations and the experimental results of the individual particle fragmentation tests, the triaxial tests, the ring shear tests and the loading tests of model pile in some types of sand with different crushabilities at various constant stress levels.
The main conclusions obtained are :
(1) Crushable soil particles are generally angular and easy to break as compared with standard geomaterials. The crushable soils have material properties such as high compressibility, large shear modulus and large internal friction angle. And a large deformation is needed to get enough soil strength.
(2) For such soils, the mechanism for the much lower mobilizing bearing capacity of the pile against settlement is clear. The end bearing capacity is caused by the material properties of crushable soils and by the effects of boundary stress around the pile.
(3) The skin friction of the pile with a smooth surface is usually occurred between the pile and the soil on slip failure. At that case it can be expressed by Coulomb's law which is the component of the friction angle and the normal pressure in different crushabilities of sands. On the other hands, it pays attention to estimate the skin friction in the case of large stress ratio.
(4) It can be shown a rational method to evaluate the bearing capacity from the results of(1)-(3).
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