循环应力历史对堆石料变形特性影响规律试验研究

为深入研究循环应力历史对堆石料变形特性的影响规律,采用大型多功能静动三轴试验机,对堆石料进行了一系列不同应力路径下的动力变形试验研究,重点探讨了循环应力历史对堆石料体应变和偏应变的影响规律.试验结果表明:堆石料经历初次循环荷载作用后,再次经受循环荷载作用时的抵抗变形能力有所提高;通过对比试验结果发现,应力路径对抵抗变形能力变化幅值的影响较小,试验时所施加的围压、固结应力比、动应力的大小等因素的影响也可忽略不计,主要与前后两次动应力大小的比值(即循环应力历史系数)有关.分析其原因,在初次循环荷载的作用下,堆石料颗粒之间发生相对滑移、旋转以及颗粒破碎等现象,导致颗粒之间的接触点增多及接触面增大,颗粒之间的咬合能力增强,形成较为稳定的骨架结构;再次施加循环荷载作用时,颗粒之间的稳定结构调整难度加大,所以导致堆石料的变形量减小,抵抗变形的能力有所提高.

Experimental study on effect of cyclic stress history on dynamic deformation of rockfill materials

In order to study the influence of cyclic stress history on the deformation characteristics of rockfill materials,a series of tests were performed on rockfill materials under different stress paths by using the triaxial apparatus. The research was focused on the influence of the cyclic stress history on volumetric strain and deviatoric strain. The experimental results show that the deformation is reduced after the cyclic stress history,which means that the ability to resist the deformation of rockfill materials is improved. Through the analysis and comparisons of the deformation of rockfill materials,the stress paths have less influence on the amplitude of resistance to deformation,and the influence of the confining pressure,the stress ratio and the magnitude of the dynamic stress can also be ignored in the experiment. The resistance to deformation is mainly related to the ratio of the two dynamic stresses( the historical coefficient of cyclic stress). The reason is that the rockfill particle is relatively sliding,rotating and breaking under the effect of cyclic stress history,which leads to the fact that the contact area increases,the bite ability strengthens,and the particles form the relatively stable skeleton structure.When the cyclic loads are applied again,the stability of the structure has difficulty in adjusting,so that the deformation of rockfill materials is reduced,and the ability to resist the deformation is enhanced.