The deformation characteristics of a kaolin clay under intermittent cyclic loadings
The deformation characteristics of a kaolin clay under intermittent cyclic loadings
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DOI：
10.1016/j.soildyn.2021.107112
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发表时间：
2022-02
影响因子：
4
通讯作者：
Zhiyong Liu;J. Xue
中科院分区：
文献类型：
--
作者：
Zhiyong Liu;J. Xue
地铁列车载荷或机器振动的特征在于间歇性循环载荷，在载荷循环之间穿插有休止期。在这种独特的循环荷载作用下，软粘土的变形可能与连续循环荷载作用下的变形不同，因为在静止或排水期间会发生再固结。对一种高岭土进行了间歇和连续两种循环加载方式下的循环三轴试验。在不同循环应力幅值、休止周期、固结围压和超固结比条件下，研究了循环加载周期之间的排水周期对粘土变形特性的影响。结果表明，包括排水周期之间的加载循环提高了循环阻力的粘土在随后的加载循环。但与连续循环加载相比，间歇加载模式下土体的轴向应变和超孔隙水压力累积量较大，且间歇时间越短，累积量越大。这意味着在加载循环之间包括再固结将扩大软粘土的最终变形。对于正常固结的试样，再固结后的应变积累高度依赖于第一个循环加载阶段的应变积累。在循环荷载作用下，超固结粘土在各循环荷载阶段累积的超孔隙水压力可以忽略不计，而轴向应变在循环荷载作用的第一阶段累积显著，之后略有增加。这可能是由于土的微结构在循环荷载作用下发生了衰减调整。
Metro train loading or machine vibration is characterized by intermittent cyclic loading interspersed with resting periods between loading cycles. The deformation of soft clay subjected to such unique cyclic loading may be different from that under consecutive cyclic loading, as reconsolidation occurs during the resting or drainage period. A series of cyclic triaxial tests were performed on a kaolin clay under both intermittent and consecutive cyclic loading patterns. The effects of including drainage periods between loading cycles on the deformation characteristic of the clay are investigated under different cyclic stress amplitudes, resting periods, consolidation confining pressures and over consolidation ratios. The results indicate that including drainage periods between loading cycles improves the cyclic resistance of the clay during subsequent loading cycles. However, compared with those under continuous cyclic loading, the overall axial strain and excess pore water pressure accumulation are much greater under the intermittent loading patterns, and the shorter the duration of resting period, the greater the overall accumulation. This means that including reconsolidation between loading cycles would enlarge the final deformation of soft clay. For the normally consolidated samples, the strain accumulation after reconsolidation highly depends on that developed in the first cyclic loading stage. Excess pore water pressure accumulated during each cyclic loading stage is negligible at given cyclic stress in over consolidated clay, whilst the axial strain accumulates notably in the first cyclic loading stage, but marginally after that. This may be attributed to the attenuation adjustment of microstructure in soil as cyclic loading continues.