Experimental Study on Vertical Bearing Capacity and Cyclic Compression Behavior of Soilbags
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摘要:
土工袋技术近年来已被成功应用于房屋地基加固，具有较好的隔震效果，但其在动荷载条件下的变形特性尚未深入研究. 为了进一步分析土工袋竖向承载能力及变形特性，开展一系列室内土工袋组合体无侧限极限抗压强度试验以及循环压缩试验，并通过控制循环次数、上部静荷载及循环荷载比值的大小研究其对土工袋组合体竖向应力、应变和动压缩模量的影响. 试验结果表明：随着层数的增加，土工袋组合体极限抗压强度逐渐减小并趋于稳定值0.7 MPa，压缩模量峰值也随之减小并稳定于6.73 MPa；循环压缩试验初期土工袋组合体塑性变形显著，每一循环周期产生的竖向残余应变随着循环次数的增加逐渐减小并趋于0；动压缩模量在试验过程中基本保持稳定，不受循环次数的影响；随着上部静荷载的增大，土工袋组合体动压缩模量逐渐增大，上部静荷载为50 kN的土工袋组合体经过200次循环荷载作用后动压缩模量达到53.87 MPa；反之，循环荷载比值越大，动压缩模量越小，循环荷载比值为0.4条件下土工袋组合体在200次循环荷载作用后仍能达到49.39 MPa；在竖向动荷载作用下，土工袋能够满足其作为隔震材料的承载能力及稳定性要求.
Abstract:Soilbags have been successfully applied to the reinforcement of building foundation with obvious effect on seismic isolation, but their deformation characteristics under dynamic load have not been studied in depth yet. In order to further analyze the vertical bearing capacity and deformation characteristics of soilbags, a series of laboratory unconfined ultimate loading tests and cyclic compression tests were conducted, and the effect of the number of loading cycles, the static load, and the cyclic load ratio on the dynamic characteristics of soilbags was studied in terms of the vertical stress-strain variation and the dynamic compression modulus. The test results show that with the increase of the number of layers, the ultimate strength of stacked soilbags decreased gradually and tended to a stable value of 0.7 MPa, and the peak compression modulus also decreased and stabilized at 6.73 MPa. An obvious plastic deformation of stacked soilbags was observed at the beginning of the cyclic compression test, and the vertical residual strain generated in each cycle decreased gradually and tended to zero with the increase of the number of cycles. The dynamic compression modulus was basically stable throughout the whole testing process, and was not affected by the number of cyclic loads. With the increase of the upper static load, the dynamic compression modulus of the stacked soilbags increased gradually. After 200 cycles of loading, the dynamic compression modulus of soilbags with the static load of 50 kN reached 53.87 MPa. However, it significantly decreased with the increased cyclic load ratio. When the cyclic load ratio was 0.4, the dynamic compression modulus of soilbags could still reached 49.39 MPa after 200 cycles of loading. In general, under the action of vertical dynamic load, the soilbags can satisfy the requirements of bearing capacity and stability as a kind of seismic isolation material.
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Key words:
- soilbags /
- compressive strength /
- cyclic loads /
- residual strain /
- dynamic compression modulus
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图 1 土工袋循环压缩试验装置示意（单位：m）
Figure 1. Schematic of cyclic compression experiment device for soilbags (unit： m)
图 4 循环压缩试验第i个循环周期竖向应力-应变示意
Figure 4. Schematic of vertical stress-strain relation during the ith loading cycle
图 5 不同层数条件下土工袋竖向承载特性试验结果
Figure 5. Test results of bearing capacities of soilbags with different layers
图 6 不同层数条件下土工袋组合体压缩模量
Figure 6. Development of compression modulus of stacked soilbags with different layers
图 7 Pstat=50 kN，Rc=0.4条件下土工袋组合体循环压缩试验结果
Figure 7. Results of cyclic compression tests of stacked soilbags under Pstat=50 kN and Rc=0.4
图 8 竖向残余应变随循环次数的变化
Figure 8. Variation of vertical residual strain of stacked soilbags with loading cycles
图 9 不同循环阶段滞回圈演化（Pstat=50 kN, Rc=0.40）
Figure 9. Evolution of hysteresis loops through different cyclic stages （Pstat=50 kN, Rc=0.40）
图 10 累积竖向应变随循环次数的变化
Figure 10. Variation of accumulated vertical strain of stacked soilbags with loading cycles
图 11 土工袋组合体动压缩模量随循环次数的变化
Figure 11. Variation of dynamic compression modulus of stacked soilbags with loading cycles
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