不同频率循环荷载下公路路基粗粒填料长期动力特性试验研究

 交通荷载作用频率随着车辆运行速度等因素变化而变化，目前对不同频率荷载下路基长期性能还缺乏一致性认识。为揭示不同频率荷载下路基粗粒土填料长期动力特性，利用GDS大型三轴试验系统对路基填料进行饱和排水循环荷载试验，分析不同应力路径下荷载频率对路基粗粒填料长期动力特性影响规律。试验结果表明，荷载频率增加使路基填料在密实阶段产生更大累积体缩应变而更密实，进而路基动力回弹模量随荷载频率增加显著增加。路基填料轴向累积变形在不同频率循环荷载下也呈现不同发展规律，路基填料密实阶段轴向累积变形在高循环应力比(ζ = 3，5)下随荷载频率增加显著增大，但在低循环应力比(ζ = 1)下，荷载频率对轴向累积变形影响较小；当填料进入变形稳定阶段，荷载频率对轴向累积变形基本无影响。该研究揭示了路基填料层在不同频率荷载下长期动力特性，发现降低路基中循环应力比，可大大减小荷载频率对路基长期动力特性影响，本研究可为准确预测和控制道路工后沉降提供参考。

Experimental study on dynamic characteristics of unbound granular materials under cyclic loading with different frequencies

The frequencies of traffic loading vary with various factors such as traffic speed. Currently there is no unified understanding in the load frequency effects on the long-term behavior of road base under the cyclic traffic loading. In order to investigate the effects of loading frequency，a series of large-scale cyclic triaxial tests on the Unbound Granular Materials(UGMs) under saturated drained condition were conducted with GDS large-scale cyclic triaxial apparatus(LDCTTS). The influence of loading frequency on the long-term performance of UGMs was investigated systematically under various stress paths. The experimental results showed that the loadings with higher frequency resulted in a larger accumulated volume contraction during the stage of densification，and consequently the UGMs reached a higher rebounding modulus. The accumulated axial strain of UGMs was also different under the loadings with different frequencies. At the stage of densification of UGMs，the loadings with the higher frequency led to higher accumulated axial strain when the cyclic stress ratios were high(ζ = 3，5)，while the loading frequency effect was minimized when the cyclic stress ratio was low(ζ = 1). After the UGMs reached the stable deformation stage，the loading frequency had almost no influence on the accumulated axial strain. This study has revealed the dynamic behavior of UGMs under the cyclic loading with different frequencies. It is found that the effects of loading frequency on the long-term performance of road base can be greatly reduced by controlling the cyclic stress ratio in the UGMs to a low level. This study can be served as reference for the accurate prediction and control of road post-construction settlement.