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Deformation and strength characteristics of geomaterials shear loaded for long term

岩土材料长期剪切荷载的变形和强度特性

基本信息

批准号：
08455218
负责人：
TATSUOKA Fumio
金额：
$ 4.54万
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：
1996
资助国家：
日本
起止时间：
1996 至无数据
项目状态：
已结题

项目摘要

The deformation characteristics at small strain levels of a wide variety of geomaterials when loaded after having been subjected to shear stress for a long duration of time in the field were investigated by means of laboratory shear tests. As the geomaterials to be tested, sand, clay, gravel, sedimentary softrock and cement-treated sand was selected. In the triaxial tests, axial strains, which were free from effects of bedding error, were measured locally from less than 0.001%.The following was found from the test results :1) Except for cement-treated soils, the deformation become elastic for some stress range when loaded again after creep deformation has occurred at a constant shear stress level. As loaded further, the stress-strain relation rejoins the primary stress-strain relation exhibiting a relatively clear yielding. This behavior can be modeled as the kinematic yielding. In some cases, the reloaded stress-strain curve overshoot exceeding the primary curve. The effects of strain rate on the deformation characteristics before the yielding upon the restart of loading is much smaller than that observed when loaded monotonously from the isotropic stress state.2) The creep rate decrease after unloaded from a higher stress level. For relatively stiff geomaterials, when unloaded to larger extents, noticeable creep recovery can be observed. This behavior leads to the effects of strain rate at unloading states in such that the tangential stiffness decreases with the decrease in the strain rate.

通过室内剪切试验，研究了多种岩土材料在野外长期剪切应力作用下的小应变变形特性。试验选用砂、粘土、砾石、沉积软岩和水泥土砂作为试验材料。试验结果表明：（1）除水泥土外，在一定剪应力水平下发生蠕变变形后，当再次加载时，在一定应力范围内变形均为弹性变形;当进一步加载时，应力-应变关系重新加入主要应力-应变关系，表现出相对明显的屈服。这种行为可以被建模为运动屈服。在某些情况下，重新加载的应力-应变曲线超过原始曲线。应变速率对屈服前的变形特性的影响远小于从各向同性应力状态单调加载时的影响。2）从较高应力水平卸载后，蠕变速率减小。对于相对刚性的岩土材料，当卸载到较大程度时，可以观察到明显的蠕变恢复。这种行为导致在卸载状态下的应变率的影响，使得切向刚度随着应变率的降低而降低。