采用机电动态单剪仪进行一系列恒体积循环单剪试验,探究了不同超固结比(overcon-solidation ratio,OCR=1~4)和不同循环应力比(cyclic stress ratio,CSR=0.21~0.53)对广州花岗岩残积土动剪切特性的影响,从滞回曲线、软化指数、动弹性模量和累积剪切变形等方面分析了花岗岩残积土的动力学特性.试验结果表明:花岗岩残积土在不同超固结比下均呈现出软化特性,软化指数随循环次数的增加而减小,在低应力水平下二者呈线性关系,而在临界循环应力比附近呈非线性关系;动弹性模量随超固结比的增大有明显衰减;花岗岩残积土存在临界循环应力比,临界值随超固结比的增大而增大.另外,基于试验结果构建了考虑超固结比、循环应力比和循环次数的累积剪切应变预测模型,可为车辆荷载下路基的变形发展预测提供参考.
A set of constant volume cyclic simple shear tests was performed to study the impacts of various cyclic stress ratio (CSR = 0.21~0.53) and overconsolidation ratio (OCR = 1~4) on the dynamic shear characteristics of granite residual soil. This study analyzed the stress-strain relationship, degradation index, dynamic elastic modulus, and cumulative shear strain of residual soil. The results showed that the granite residual soil exhibited softening behavior at different overconsolidation ratios. The softening index decreased with an increasing number of cycles, showing a linear relationship at low stress levels and a nonlinear relationship near the critical cyclic stress ratio. The dynamic elastic modulus exhibited significant attenuation with an increase in OCR. The threshold for the cyclic stress ratio increases with higher overconsolidation ratios under cyclic loading. In addition, a prediction model for the cumulative shear strain was developed considering the overconsolidation ratio, cyclic stress ratio, and number of cycles. This research provides valuable insights for analyzing the cumulative deformation of granite residual soil subgrades under traffic loads.
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