2000 Fiscal Year Final Research Report Summary
| Project/Area Number |
11450180
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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 | University of Tokyo |
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Principal Investigator |
TATSUOKA Fumio The University of Tokyo, Department of Civil Engineering, Professor, 大学院・工学系研究科, 教授 (70111565)
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| Co-Investigator(Kenkyū-buntansha) |
HAYANO Kimoitoshi The University of Tokyo, Institute of Industrial Science, Assistant, 生産技術研究所, 助手 (40302632)
UCHIMURA Taro The University of Tokyo, Department of Civil Engineering, Assistant, 大学院・工学系研究科, 助手 (60292885)
TOWHATA Ikuo The University of Tokyo, Department of Civil Engineering, Professor, 大学院・工学系研究科, 教授 (20155500)
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| Project Period (FY) |
1999 – 2000
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| Keywords | stiff geomaterial / deformation characteristics / time effect / viscous effect / creep / stress relaxation / unloaded conditions / effects of strain rate |
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| Research Abstract |
The time effects on the deformation characteristics under unloaded conditions of stiff geomaterials, such as Pleistocene clays, sand/gravel, sedimentary soft rock and cement-mixed soils, were studied theoretically and experimentally. The proper prediction of this behavior is important for many practical issues, such as evaluation of preloading effects, time-dependent deformation or ground subjected to excavation and interpretation of the unloading behavior in the field loading tests. From the present study, the following conclusions were obtained commonly with various stiff geomaterials tested in the present study :
1) Even after unloading is started at a constant load rate from a certain loaded state, the increase in the deformation continues at a decreasing rate.
2) When the load level is decreased to a certain level, the rate of irreversible deformation rate becomes zero.
3) When the load level is further decreased, the irreversible deformation rate becomes negative, while the deformat
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ion decreases with time at a creep stage and the load increases with time at a relaxation stage.
Most of the existing theories on the time-effects on the deformation characteristics of geomaterials deal with the deformation during loading stage. In view of the above, the following constitutive models were developed to explain the above.
1) New isotach model ; a given strain increment is decomposed into the elastic and irreversible components, while a given stress is decomposed into the inviscid and viscous components. The hysteretic relationships between the inviscid stress and the irreversible strain for loading, unloading and so on are defined. Then, the current stress state for a given stress history is uniquely controlled by instantaneous irreversible strain and its rate. This model is relevant to several types of clay and sedimentary softrocks.
2) TESRA (temporary effects of strain rate and acceleration) model : the current viscous stress is obtained by integrating with respect to the irreversible strain the viscous stress increment by the increase in the irreversible strain and that by the increase in the irreversible strain rate. In this integration, a decay of these two types of viscous stress increments with the irreversible strain is taken into account. This model is relevant to poorly graded sands. Less
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[Publications] Matsushita,M.,Tatsuoka,F.,Koseki,J.,Cazacliu,B.,Di Benedetto,H.and Yasin,S.J.M.: "Time effects on the pre-peak deformation properties of sands"Proc.Second Int.Conf.on Pre-Failure Deformation Characteristics of Geomaterials, IS Torino'99 (Jamiolkowski et al., eds.), Balkema. Vol.1. 681-689 (1999)
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「研究成果報告書概要(和文)」より
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[Publications] Tatsuoka,F.,Santucci de Magistris,F.,Hayano,K.,Momoya,Y.and Koseki,J.: "Some new aspects of time effects on the stress-strain behaviour of stiff geomaterials"Keynote Lecture, The Geotechnics of hard Soils-Soft Rocks, Proc.of Second Int.Conf.on hard Soils and Soft Rocks,Napoli,1998 (Evamgelista and Picarelli eds.), Balkema. Vol.2. 1285-1371 (2000)
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