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Three-dimensional visco-elasto-plastic stress-strain-properties at small strains of stiff geomaterials

刚性岩土材料小应变下的三维粘弹塑性应力应变特性

基本信息

批准号：
09450180
负责人：
TATSUOKA Fumio
金额：
$ 3.58万
依托单位：
The 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：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Elasto-plastic stress-strain properties, as well as viscous properties (time-dependent properties), of stiff geomaterials under three-dimensional stress conditions were investigated by performing special tests using advanced triaxial and plane strain apparatuses. Specimens of stiff clays, sands, gravels, silty sand and sedimentary soft rocks were subjected to tests in which different constant strain rates were maintained, the constant axial strain rate was changed stepwise or the rate of strain rate was kept constant at several stages. For quasi-elastic stress-strain properties at strains less than about 0.001%, a hypo-elasticity model was proposed, for which the elastic constants are specific functions of instantaneous stresses. As to the viscous properties, the isotach model was found relevant to soft clays and a silty sand. A simple isotach model is proposed, in which the current stress is a unique function of the instantaneous irreversible strain and irreversible strain rate, and the current stress increment is a unique function of the instantaneous elastic strain increment. It was found that with clean sands, the isotach model is not relevant, and the shear stress and shear strain relationships are essentially independent of constant strain rates differing by a factor up to 500. It was also found that the stress level noticeably and temporarily increased and decreased when the strain rate increased and decreased stepwise (i.e., when a time history of strain acceleration and deceleration was given). Similarly, with a time history of strain deceleration, the sands exhibited noticeable creep deformation and stress relaxation.

采用先进的三轴应变仪和平面应变仪，通过特殊试验研究了三维应力条件下刚性岩土材料的弹塑性应力-应变特性以及粘性特性（时间相关特性）。对硬粘土、砂、砾石、粉砂和沉积软岩试样进行了不同的恒应变速率、恒轴向应变速率逐级变化和恒轴向应变速率分阶段变化的试验。对于应变小于0.001%时的准弹性应力-应变特性，提出了一种次弹性模型，其弹性常数是瞬时应力的特定函数。对于粘性特性，等速线模型适用于软粘土和粉砂。提出了一个简单的等速线模型，其中当前应力是瞬时不可逆应变和不可逆应变率的唯一函数，当前应力增量是瞬时弹性应变增量的唯一函数。结果发现，与干净的沙子，等速度模型是不相关的，和剪切应力和剪切应变的关系基本上是独立的恒定应变率不同的一个因素高达500。还发现当应变速率逐步增加和降低时（即，当给出应变加速和减速的时间历程时）。同样，随着应变减速的时间历程，砂土表现出明显的蠕变变形和应力松弛。