循环剪切作用下土工袋组合体动力特性试验研究

Experimental study on dynamic characteristics of stacked soilbags under cyclic shear loading

土工袋具有承载力高、阻尼大、造价低等诸多优点,是一种适用于村镇地区中、低层房屋的减/隔震材料。通过开展室内循环剪切试验对土工袋组合体的剪切应力⁃剪切应变关系、动力特性参数以及抗剪强度进行分析讨论,探究不同竖向应力与剪切应变幅值条件下土工袋组合体动剪切模量与等效阻尼比的变化规律,同时研究了循环次数对土工袋组合体动力特性参数以及抗剪强度参数的影响。试验结果表明:在小变形情况下,土工袋组合体的峰值剪切应力和动剪切模量随着循环次数的增加而逐渐增大,等效阻尼比则随着循环次数的增加而逐渐减小;在大变形情况下,土工袋组合体发生层间滑移并出现界面软化现象,此时的峰值剪切应力(抗剪强度)随着循环次数的增加而逐渐减小,动力特性参数随循环次数的变化与小变形情况下完全相反。随着循环次数的增加,土工袋组合体的抗剪强度参数似摩擦角逐渐减小,似黏聚力逐渐增大并趋于稳定。在剪切应变幅值较大的情况下,土工袋组合体通过袋内土体的剪切变形以及土工袋层间滑移产生摩擦耗能,具有较好的减振消能效果。

Soilbag,with the advantages of high bearing capacity,high damping ratio and low cost,is a kind of base isolation materi⁃al which is suitable for the low-and mid-rise buildings.The relationship between shear stress-shear strain,dynamic characteristic parameters and shear strength of stacked soilbags were analyzed and discussed through a series of laboratory cyclic simple shear tests.The variation of dynamic shear modulus and equivalent damping ratio of stacked soilbags under different vertical stresses and shear strain amplitude was further investigated.And the influence of number of load cycles on the dynamic characteristic parameters and shear strength parameters was also studied.The test results show that the peak shear stress and dynamic shear modulus in⁃crease while the equivalent damping ratio decreases with the increasing number of load cycles under small-strain condition;when the shear strain is large enough,the interface slippage and the strain softening occur on stacked soilbags.The peak shear stress(shear strength)decreases with the increasing number of load cycles.And the variation of dynamic characteristic parameters is to⁃tally opposite to that under small-strain condition.The internal friction angle of the shear strength parameters of stacked soilbags gradually decreases with the increasing number of load cycles while the additional cohesion force increases and tends to be stable during the test.The energy is dissipated through the shear deformation of soil particles inside bags and the interlayer slippage of stacked soilbags under high shear strain amplitude.