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地盤材料の変形特性に対する時間効果の新しい展開

地基材料变形特性时间效应的新进展

基本信息

批准号：
11450180
负责人：
TATSUOKA Fumio
金额：
$ 5.25万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450180/
关键词：
stiff geomaterial deformation characteristics time effect viscous effect creep stress relaxation unloaded conditions effects of strain rate ひずみ速度ひずみ加速度リラクゼーション ageing

项目摘要

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 … More 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

从理论和试验两方面研究了更新世粘土、砂砾石、沉积软岩和水泥土等硬质岩土材料在卸载条件下变形特性的时间效应。这一特性的正确预测对于预压效果的评价、开挖过程中土体的时变变形以及现场载荷试验中卸载特性的解释等许多实际问题都具有重要意义。通过对各种刚性岩土材料的试验研究，得到如下结论：1)即使在某一加载状态下以恒定的加载速率开始卸载，变形的增加也是以递减的速度进行的；2)当加载水平降低到一定程度时，不可逆变形率变为零；3)当加载水平进一步降低时，不可逆变形速率变为负值，而变形…在蠕变阶段，更多的离子随着时间的推移而减少，在松弛阶段，载荷随着时间的推移而增加。现有的岩土材料变形特性的时间效应理论大多针对加载阶段的变形。有鉴于此，建立了如下本构模型来解释上述问题：1)新的本构模型：将给定的应变增量分解为弹性和不可逆分量，而将给定的应力分解为无粘性和粘性分量。定义了无粘应力与加载、卸载等不可逆应变之间的滞回关系。然后，给定应力历史的当前应力状态由瞬时不可逆应变及其速率唯一地控制。该模型适用于几种类型的粘土和沉积软岩。2)TESRA(应变率和加速度的临时效应)模型：当前粘性应力是通过对不可逆应变、不可逆应变的增加和不可逆应变率的增加而增加的粘性应力进行积分而得到的。在这种积分中，考虑了这两种类型的粘性应力增量随不可逆应变的衰减。该模型适用于级配较差的砂岩。较少