橡胶掺量对格栅-橡胶砂界面宏细观剪切特性影响

Effects of rubber content on macro-and meso-scopic shear characteristics of geogrid-rubber sand interface

为了研究土工格栅–橡胶砂界面的剪切特性,通过室内大型直剪仪,分析了不同橡胶掺量、相对密实度和竖向应力下界面的剪应力–剪切位移关系及体变特性;并基于室内试验,建立关于PFC^(3D)的纯砂和橡胶砂直剪模型,揭示土工格栅加筋橡胶砂在直剪过程中的细观力学机理。研究表明:在相同密实下橡胶砂剪切强度随着橡胶掺量增加先增大后减小,其最优橡胶掺量为10%,且越松散由橡胶掺量引起的剪切强度差(|τ0-τ50|)越大;在纯砂中掺入一定量橡胶颗粒能增大其似黏聚力和内摩擦角,但影响其剪切强度以内摩擦角为主;橡胶颗粒掺入致使剪切带相对厚度变小,橡胶颗粒对砂颗粒的转动起抑制作用,使得橡胶砂的孔隙率的变化量小于纯砂;橡胶砂组构分布能够反映接触力的分布,整体上颗粒间接触点数量比纯砂的略多,法向接触力和切向接触力比纯砂小;橡胶颗粒掺入增大了体系的阻尼耗能,提高了混合物的弹性。

A large-scale direct shear apparatus is used to study the interface shear properties of the geogrid-reinforced rubber-sand mixture.The variations of shear stress with shear displacement and volume deformation characteristics are analyzed under different rubber contents,relative densities and normal stresses.Based on the indoor experiments,direct shear models for sand and rubber-sand mixture on PFC^(3D) are established to reveal the meso-mechanical mechanism of geogrid-reinforced rubber-sand mixture in the direct shear process.The results show that the shear strength of rubber-sand mixture rises first and then drops with the increase of rubber content under the same compaction.The optimal rubber content is 10%.The looser the mixture is,the greater the difference is in shear strength(|τ0-τ50|)caused by the rubber content.Adding some rubber particles in sand can increase its apparent cohesion and interface friction angle,but the shear strength is mainly affected by the latter.The relative thickness of the shear band becomes smaller in view of the entry of rubber particles.The rubber particles inhibit the rotation of the sand particles,making the porosity change of the rubber-sand mixture smaller than that of the sand.The fabric distribution of the rubber-sand mixture can reflect the distribution of contact force,and the number of touch points among particles is a little more than that of the sand.The normal contact force and tangential contact force of the mixture are smaller than those of sand.The addition of rubber particles increases the damping energy consumption of the system and improves the elasticity of the mixture.