先期振动对高聚物胶凝堆石料动变形特性的影响

先期振动对土石坝地震变形影响显著。通过开展不同先期动应力作用下的动三轴试验,研究了先期振动对未加固堆石料和高聚物胶凝堆石料动变形特性的影响。结果表明:先期振动对未加固堆石料和高聚物胶凝堆石料的弹性轴应变无明显影响,但显著降低了其塑性轴应变;未加固堆石料和高聚物胶凝堆石料的残余变形在先期振动影响下显著减小,与未经受先期振动的试样相比,先期动应力为40%围压的试样,最大残余剪应变降低幅度和最大残余体应变降低幅度的平均值分别为48.1%和42.0%;先期动应力为80%围压的试样,最大残余剪应变降低幅度和最大残余体应变降低幅度的平均值分别为80.9%和71.6%。先期动应力幅值越大,再次经历动应力时未加固堆石料和高聚物胶凝堆石料产生的残余变形越小,抵抗变形能力提高越明显。最大残余变形的降低幅度与固结比、围压及高聚物含量无关。随后修正了沈珠江动残余变形模型,修正后的残余变形模型可以反映高聚物对堆石料残余剪应变和残余体应变的影响。与未经受先期振动的试样相比,先期动应力为40%围压的高聚物胶凝堆石料(高聚物质量比R_p=2%)的改进残余变形模型参数c₁和c₄分别降低了27.7%和61.2%;先期动应力为80%围压的高聚物胶凝堆石料(R_p=2%)的改进残余变形模型参数c₁和c₄分别降低了68.8%和79.3%。

Effect of Previous Cyclic Loading on Dynamic Deformation Behaviors of PFA-reinforced Rockfill Materials

Previous cyclic loading has a significant influence on the dynamic deformation of rockfill dams during an earthquake. A series of cyclic triaxial shear tests were carried out to investigate the dynamic deformation behaviors of polyurethane foam adhesive (PFA) reinforced rockfill materials and determine the corresponding effects of the amplitude of the previous cyclic loading, PFA content, initial stress ratio, and confining pressure. The test results show that the plastic axial strain of unreinforced and PFA-reinforced rockfill materials decreases significantly with increasing amplitude of the previous cyclic loading. In contrast, the effect of the previous cyclic loading on the elastic axial strain is negligible. The influence of previous vibration on the residual deformation of unreinforced and PFA-reinforced rockfill materials is analyzed. The previous cyclic loading significantly reduces the residual deformation of unreinforced and PFA-reinforced rockfill materials. Under the condition that the amplitude of the previous cyclic loading is equal to 0.4 times the confining pressure, the average reductions of the maximum residual shear strain and the maximum residual volumetric strain of the PFA-reinforced rockfill materials are 48.1% and 42.0%, respectively. Under the condition that the amplitude of the previous cyclic loading is equal to 0.8 times the confining pressure, the average reductions of the maximum residual shear strain and the maximum residual volumetric strain of the PFA-reinforced rockfill materials are 80.9% and 71.6%, respectively. With increasing amplitude of the previous cyclic loading, the residual deformation of unreinforced and PFA-reinforced rockfill materials decreases significantly, and the capability to resist deformation tends to increase. The reduction in the maximum residual deformation is independent of the initial stress ratio, confining pressure, and PFA content. Based on the test results, the residual deformation model presented by Shen Zhu-jiang was modified. The modified model can depict the effect of PFA on the residual deformation of rockfill materials. Compared with the specimens that are not affected by previous vibration, the modified residual deformation model parameters c₁ and c₄ of PFA-reinforced rockfill materials (R_p=2%), under the condition that the amplitude of the previous cyclic loading is equal to 0.4 times the confining pressure, are reduced by 27.7% and 61.2%, respectively. Under the condition that the amplitude of the previous cyclic loading is equal to 0.8 times the confining pressure, the reductions of c₁ and c₄ are 68.8% and 79.3%, respectively.