法向循环荷载下土石混合料-格栅界面剪切特性研究

Study on Shear Characteristics of Soilrock Mixture‑geogrid Interface under Normal Cyclic Loading

摘要:

土石混合料作为被广泛应用的路基填料，其与土工格栅的加筋结构作为承担与传递交通荷载的重要载体，强度与稳定性受筋土界面在法向循环荷载下的动力剪切特性影响。采用大型动态直剪仪，对土石混合料?格栅界面进行了一系列动力直剪试验。分析了法向加载频率（0.05、0.1、1 Hz），法向应力振幅（20、40、60 kPa）对不同细粒含量 （0%，20%，40%，60%，80%，100%）下土石混合料?格栅界面剪切特性的影响。结果表明：在法向循环荷载作用下， 剪切应力与法向位移均呈现周期性变化。界面抗剪强度随细粒含量增加呈现先增大后减小的趋势，在 40% 细粒含量时达到最大值。界面抗剪强度随振幅增大而增大，随频率增大而减小。增大细粒含量会使得界面剪缩效应减小，而增大振幅以及频率会使得界面剪缩效应增大。界面摩擦系数与法向应力间呈现相同的周期性变化，并存在 0.5 个周期左右的相位差。界面摩擦系数在峰值与残余阶段均随细粒含量增大呈现先增大后减小的趋势。

Abstract:

As a widely used subgrade filler, soil-rock mixtures form reinforced structures with geogrids that serve as critical components for bearing and transferring traffic loads. Their strength and stability are affected by the dynamic shear characteristics at the soil-reinforcement interface under normal cyclic loading. A series of dynamic direct shear tests were conducted on soil-rock mixture-geogrid interface using a large-scale dynamic shear apparatus. The effects of normal loading frequency (0.05, 0.1, 1 Hz) and normal stress amplitude (20, 40, 60 kPa) on the interface shear characteristics of soilrock mixture-geogrid interface at different fines content (0%, 20%, 40%, 60%, 80%, 100%) were analyzed. The results showed that under normal cyclic loading, both the shear stress and normal displacement exhibited periodic variations. The interface shear strength initially increased and then decreased with increasing fines content, reaching its maximum value at a 40% fines content. Furthermore, the interface shear strength increased with the amplitude but decreased with the frequency. Increasing fines content reduced interface shear shrinkage, whereas increasing the amplitude and frequency enhanced it. The interface friction coefficient and normal stress demonstrated the same periodic variation, with a phase difference of approximately 0.5 cycles. Notably, the interface friction coefficient, both at peak and residual stages, showed a trend of first increasing and then decreasing as the fines content rose.