1996 Fiscal Year Final Research Report Summary
EVALUATION OF DYNAMIC SOIL-PILE-STRUCTURE INTERACTION DURING SOIL LIQUEFACTION AND CYCLIC MOBILITY
| Project/Area Number |
07455216
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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 |
Building structures/materials
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| Research Institution | TOKYO INSTITUTE OF TECHNOLOGY |
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Principal Investigator |
TOKIMATSU Kohji Professor, Faculty of Engineering Tokyo Institute of Technology, 工学部, 教授 (50134846)
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| Co-Investigator(Kenkyū-buntansha) |
SHAMOTO Yasuhiro Senior Research Engineer, Shimizu Corporation, 技術研究所, 主任研究員
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| Project Period (FY) |
1995 – 1996
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| Keywords | Pile / Interaction / Ground displacement / Whincler foundation / Centrifugal model test / Earthquake / Bending moment |
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| Research Abstract |
The conditions causing soil liquefaction and resulting damage to building foundations in the 1995 Hyogoken-Nambu earthquake are examined. It is shown that possible causes fo the foundation damage include : (1) horizontal forces and overturning moments imposed on the foundation from the superstructures, (2) kinematic forces acting on deep foundations due to shear deformation of soils, (3) reduction in bearing capacity due to ground failures including liquefaction, and (4) lateral spreading.
Both failure and deformation modes are examined using a borehole camera and a slope-indicator for prestressed concrete piles of buildings that experienced liquefaction-induced ground displacement during the 1995 Hyogoken-Nambu earthquake. It is shown that the damage is concentrated at the interface between liquefied and non-liquefied layrs, suggesting the significant effect of ground displacement on pile damage.
Centrifuge shaking table tests are conducted on a soil-pile-structure model to investigate the effects of ground displacement and inertia force from the superstructure on stresses in piles during soil liquefaction. It is shown that the ground displacement and inertia force are in phase if the natural period of the structure is less than that of the soil deposit, whereas they are out of phase if the natural period of the structure is greater than that of the soil deposit.
An analytical model is then proposed in which a group of piles connected with the same foundation is subjected to lateral ground displacement and inertia force, and the stress and displacement of the piles are calculated. The computed failure and deformation modes agree reasonably well with the field observations, confirming that the proposed analytical model could be effectively used to estimate stresses in piles during soil liquefaction.
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