橡胶-砂颗粒混合物压缩特性与胶结退化试验

为揭示轻度胶结橡胶-砂颗粒混合物的压缩特性和胶结退化过程，通过室内一维压缩试验、剪切波速测试和扫描电镜检测，对比分析混合物的应力-应变特征和刚度演化规律，研究颗粒间胶结作用、砂掺量等对试样密度、残余应变、剪切波速和小应变剪切模量的影响，同时定性评价压缩后胶结混合物微观结构特征，探讨轻度胶结刚-柔性颗粒混合物的受力变形机制。试验结果表明：橡胶-砂颗粒混合物密度随砂掺量增加呈线性增加趋势；少量胶结物质添加可有效减小压缩变形和残余应变，胶结试样的加载压缩曲线可分为胶结控制、胶结退化和应力控制3个阶段，残余应变与砂掺量间呈指数减小关系；颗粒间胶结作用在高应力条件下退化完全，胶结试样剪切波速表现出与未胶结试样相似的变化规律；相同砂掺量与应力条件下，胶结试样具有较高的小应变剪切模量，压缩过程中小应变剪切模量的演化规律与剪切波速类似；颗粒间胶结在荷载作用下首先发挥作用并逐渐退化，当刚性颗粒（砂颗粒）含量较低时，混合物的受力介质主要为柔性颗粒（橡胶颗粒），颗粒空间位置无显著改变；当刚性颗粒含量较高时，荷载作用下刚性颗粒会发生一定的滑移和滚动，形成相互接触的受力链以承受荷载，柔性颗粒则可阻止受力链倾覆与倒塌。

Experimental on Compression Characteristics and Bonding Degradation of Rubber-sand Mixtures

To illustrate the compression characteristics and bonding degradation of lightly cemented rubber-sand mixtures, a series of laboratory tests including the one-dimensional compression test, shear wave velocity measurement, and scanning electron microscopy analysis are conducted to study the stress-strain characteristics and evolution of the stiffness of the rubber-sand mixtures. The effects of the bonding between particles and sand fraction on the density, residual strain, shear wave velocity, and small-strain shear modulus are investigated. Moreover, the microstructure characteristics of the lightly cemented mixtures after the compression are qualitatively evaluated to explore the deformation mechanism of this material. The experimental results show that the density of the rubber-sand mixtures increases linearly with the increase in the sand fraction. The addition of a small amount of bonding material effectively reduces both the compression deformation and residual strain. The compression curves of the lightly cemented samples during the loading stage can be divided into three types:bonding control, bonding degradation, and stress control. An exponential decreasing correlation between the residual strain and sand fraction is found in this study. Under high-stress conditions, the bonding between the particles is completely degraded, and the variation in the shear wave velocity with the stress of the lightly cemented mixtures is similar to that of uncemented mixtures. Under the same sand fraction and stress conditions, the lightly cemented mixtures possess a larger small-strain shear modulus than the uncemented mixtures, and the evolution of the small-strain shear modulus during the compression process is similar to the shear wave velocity. Once the loading is applied on the mixtures, the bonding between the particles is the first to play a role and is gradually degraded. When the mixtures contain fewer rigid particles, the content of the rigid particles (sand particles) is low, and soft particles (rubber chips) are employed to support the loading, and the spatial position of these two particles is not changed obviously. However, sliding or rolling occurs between the rigid particles and some force chains are generated to support the external loading when the content of the rigid particles is high. Soft rubber chips often play an important role in preventing the slipping and buckling of rigid particle chains.