橡胶颗粒-砂混合物新型路基填料动力参数特性的试验研究

橡胶材料具有密度低、线弹性变形能力强、耐久性好、耗能大等优点，其衍生物与土体制成的混合物被广泛应用于岩土工程和交通工程领域。为研究橡胶颗粒与砂土混合物这种新型路基填料在循环列车荷载作用下的动力参数特性，进行室内固结不排水动三轴试验，分析了橡胶颗粒含量、围压以及加载频率等因素对橡胶颗粒-砂混合物动剪切模量、阻尼比等特性的影响，研究结果表明：应变一定时，混合物的动剪切模量随着橡胶颗粒含量的增加而减小，随着围压的增大而增大，随着加载频率的增加而轻微减小；基于Hardin-Drnevich双曲线模型对动剪切模量试验结果进行拟合，得出最大动剪切模量，发现最大动剪切模量随着橡胶颗粒含量的增加而减小。应变一定时，混合物的阻尼比随着橡胶颗粒含量的增大而增大，随着围压的增大而减小，加载频率对阻尼比的影响较小；基于试验结果，建立了橡胶颗粒-砂混合物阻尼比与剪切应变的关系式。最后，基于柔性橡胶颗粒与刚性砂土颗粒的微观接触特性，分析了橡胶颗粒对混合物动剪切模量以及阻尼比的影响机理。综合研究结果得出：橡胶颗粒含量不宜超过20%，此时橡胶颗粒-砂混合物作为新型路基填料的动剪切模量可以满足要求，阻尼比较大，具有良好的减震耗能效果。

Experimental Study on Dynamic Parameter Characteristics of New Subgrade Filler Composed of Granular Rubber-Sand Mixtures

Tire rubber material has the advantages of low density, strong linear elastic deformation ability, good durability and high energy consumption. The mixture of tire rubber derivatives and soil is widely used in geotechnical engineering and traffic engineering. In order to study the dynamic parameter characteristics of granular rubber-sand mixtures (which is a new type of subgrade filler) under cyclic train loading, the indoor consolidated undrained dynamic triaxial test was carried out. The effect of granular rubber content, confining pressure and loading frequency on shear modulus and damping ratio characteristics of the granular rubber-sand mixtures were studied. The research results showed that when the shear strain is constant, the shear modulus decreased with the increase of granular rubber content, increased with the increase of confining pressure and decreased with the increase of loading frequency. Based on the well-known hyperbolic law used by Hardin and Drnevichin, the shear modulus test results were fitted to obtain the maximum shear modulus, and the maximum shear modulus decreased with the increase of granular rubber content. When the shear strain is constant, the damping ratio of the granular rubber-sand mixtures increased with the increase of granular rubber content, and decreased with the increase of confining pressure. Based on the experimental results, the relationship between damping ratio and shear strain was established. In addition, based on the microstructure characteristics of flexible rubber particles and rigid sand particles, the influence mechanism of granular rubber on shear modulus and damping ratio of the mixtures was analyzed. According to the comprehensive research results, it can be concluded that the highest granular rubber content in the new subgrade filler is 20%. When the granular rubber content is not greater than 20%, the shear modulus of the new subgrade filler can meet the requirements and the damping ratio is relatively large, and it has a good damping and energy dissipation effect.