单、双向振动条件下饱和粉砂变形特性对比试验研究

由于仪器水平的限制,关于土体的动力特性的研究目前多采用单向激振方式替代双向激振方式。而这两种激振方式在试验原理方面存在明显不同。很多研究表明,应力路径对土的响应有着不可忽视的影响,这两种方式相替代的合理性尚待证明。本文利用DSC2000多功能动三轴试验系统,选取尾矿砂分别在单向及双向振动条件下进行一系列饱和土的动力特性试验,对比两种激振方式作用下土体的滞回曲线以及骨干曲线的差异,分析土体在这两种振动方式下产生差异的原因,并应用双曲线模型对骨干曲线进行拟合,最后给出在进行土体变形特性试验时以单向激振方式替代双向激振方式的适用条件。

Study on Deformation Characteristics of Saturated Silty Sand in Uni-and Bidirectional Cyclic Triaxial Tests

When evaluating the dynamic characteristics of sandy deposits during earthquakes, the analysis method proposed by Seed is the one almost always adopted. In addition, a unidirectional dynamic cyclic triaxial test rather than a bidirectional one is often used by researchers to determine the dynamic characteristics of sandy deposits. The validity of these methods is called into question considering that the dynamic stress paths induced by uni-and bidirectional cyclic triaxial tests are not the same. In this study, a dynamic triaxial apparatus, capable of vertical and radial dynamic loading, was used to compare uni-and bidirectional cyclic triaxial tests on saturated silty sand. Comparison of the results showed differences in both the hysteresis loops and skeleton curves produced by each method; both deformation and energy dissipation were larger in the unidirectional test; this was found to be a result of spherical stress. A hyperbolic model that perfectly matched the skeleton curves for both sets of test results was then established. Finally, cell pressure was identified as the key factor affecting the test conditions, resulting in the difference between the two methods. A suggested initial cell pressure value is established and given for the tested material.