2006 Fiscal Year Final Research Report Summary
Constitutive models for sands under dynamic loading and constitutive parameters estimated based on SPT blow count N
| Project/Area Number |
17560442
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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 | Tokyo Institute of Technology |
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Principal Investigator |
OHTA Hideki Tokyo Institute of Technology, Dept. of International development engineering, Professor, 大学院理工学研究科, 教授 (80026187)
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| Co-Investigator(Kenkyū-buntansha) |
KUSAKABE Osamu Tokyo Institute of Technology, Dept. of civil engineering, Professor, 大学院理工学研究科, 教授 (40092548)
TAKEMURA Jiro Tokyo Institute of Technology, Dept. of civil engineering, Associate Professor, 大学院理工学研究科, 助教授 (40179669)
KUWANO Jiro Geosphere Research Institute of Saitama University, Professor, 地圏科学研究センター, 教授 (30178149)
IZAWA Jun Tokyo Institute of Technology, Dept. of civil engineering, Assistant Professor, 大学院理工学研究科, 助手 (70345388)
IIZUKA Atsushi Kobe University, Research Center for Urban Safety and Security, Professor, 都市安全研究センター, 教授 (40184361)
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| Project Period (FY) |
2005 – 2006
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| Keywords | elastic-plastic constitutive model / numerical analysis / constant volume triaxial test / SPT blow count N / computer simulation / field monitoring / parameter estimation procedure / dynamic analysis |
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| Research Abstract |
Two world-wide well known elastic-plastic constitutive models, the Original Cam Clay model and the Modified Cam Clay model, are extended into anisotropic forms applicable to Ko-consolidated natural soil deposits and further extended into forms appropriate to describe the soil behaviour under repeated loading by using the concepts both of extended sub-loading surface and super-loading surface proposed by Hashiguchi et al (1998) and Asaoka et al (2002) respectively. Examination of these two extended models from the theoretical and numerical points of view indicates that they are employable in engineering practice under limited conditions and suggests the need of developing a family of constitutive models applicable to wider variety of sandy soils. The newly developed family of models includes the Original and Modified Cam Clay models and is found to be applicable to wide variety of natural soil deposits.
Undisturbed block samples of dense fine sand taken from a tunneling site are subjecte
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d to a series of constant volume triaxial tests under very high confining pressure. The constitutive parameters obtained from the triaxial tests are carefully compared with the blow count N obtained from the Standard Penetration Tests carried out at the tunneling site aiming at correlating the blow count N with the parameters needed in constitutive models. Confirmation of the relationship between the blow count N and undrained shear strength of sand empirically proposed by Nishigaki et al (1974, 1980) is one of the aims.
A procedure of parameter estimation for sandy deposits based on the blow count N from the SPT is thus developed and examined how it works in the engineering practice by employing in a computer simulation of a deep excavation work carried out at a site of sandy deposit. The results obtained from this trial computer simulation using a soil/water coupled finite element code incorporating the newly developed constitutive model are found to be satisfactory by comparing with monitored bending moment and deformation of sheet pile wall installed in the sandy deposit being excavated. It is concluded that the constitutive parameters of sandy deposits for which the SPT blow count N is often the sole available information on mechanical properties can be estimated based primarily on the blow count N and applicable in engineering practice. Less
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