水平循环剪切作用下土工袋竖向变形特性试验研究

Experimental study on the vertical deformation performance of soilbags under horizontal cyclic shear loading

土工袋作为一种地基加固材料在工程中的应用越来越广泛,研究表明土工袋具有较高的阻尼比,能够有效地消能并阻隔地震波由场地向上部结构的传递。为了解土工袋在水平循环荷载作用下的竖向变形特性,开展了一系列土工袋组合体的水平循环剪切试验,研究了循环次数、竖向应力以及剪切应变幅值等加载特征对土工袋组合体竖向变形的影响,探讨了水平循环荷载作用下土工袋组合体的变形机制。结果表明:(1)土工袋组合体的累积竖向应变在试验初期变化较为显著,随着循环次数的增加,其累积竖向应变逐渐趋于稳定;(2)竖向应力和剪切应变幅值对土工袋组合体的竖向应变影响显著,随着竖向应力与剪切应变幅值的增大,其竖向应变也随之增加;(3)土工袋组合体在较大剪切应变幅值条件下开始出现层间滑移,试验初期土工袋组合体在层间滑移阶段竖向应变基本保持稳定,但是随着循环次数的增加,土工袋组合体层间界面反复摩擦使层间的咬合作用发生变化,靠近土工袋组合体层间界面的砂土颗粒在此过程中又进行了重新排列,最终导致试验后期土工袋组合体单次循环产生的竖向应变增量呈现出增长趋势。

Soilbags have been gradually widely used in projects as a kind of foundation reinforcement material.Some studies show that soilbags,with a relatively higher damping ratio,could effectively dissipate the energy and reduce the transmission of seismic waves from foundation to superstructure.In order to investigate the deformation performance of soilbags under horizontal cyclic loads,a series of horizontal cyclic shearing tests were conducted considering the influences of the loading characteristic parameters including the number of load cycles,vertical stress and shear amplitude on the vertical deformation of soilbags,and the deformation mechanism of stacked soilbags under horizontal cyclic loads was discussed.The test results show that:(1)the accumulated vertical strain increases gradually at the initial stage and subsequently gets stable with the increasing of the number of load cycles.(2)the vertical strain of stacked soilbags is greatly influenced by the vertical stress and shear amplitude,and increases with the increasing vertical stress and shear amplitude.(3)the interface slippage of stacked soilbags occurs under higher shear amplitude.The vertical strain of stacked soilbags under slipping condition keeps stable at the initial stage of tests.However,the incremental vertical strain is gradually amplified with the increasing of the number of load cycles owing to the rearrangement of infilled soil particles close to the interface between soilbags due to the weakening of shear strength at the interface induced by the repeated slippage and friction.