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.

通过实验室剪切测试，研究了在野外长时间长时间长时间施加剪切应力后，在较长的剪切应力后加载时，在各种地材料的小应变水平下的变形特性。作为要测试的地材料，选择了沙子，粘土，砾石，沉积物索岩和水泥处理的砂。在三轴测试中，轴向菌株没有层中的误差的影响，在局部从小于0.001％测量。从测试结果中找到以下结果：1）除水泥处理的土壤外，在蠕变后再次加载时，在恒定的剪切应力水平上再次加载时，在某些应力范围内再次弹性。随着进一步的加载，应力 - 应变关系重新加入了表现出相对清晰的屈服的主要应力 - 应变关系。这种行为可以建模为运动学屈服。在某些情况下，重新加载的应力应变曲线超过了主要曲线。应变速率对重新载荷重新载荷之前产量之前的变形特性的影响要比各向素质应力状态单调时观察到的影响要小得多。2）2）从较高的应力水平卸载后，蠕变速率降低。对于相对僵硬的土地材料，当卸载到较大的范围时，可以观察到明显的蠕变恢复。这种行为会导致卸载状态下应变率的影响，从而随着应变率的降低而切向刚度会降低。