橡胶砂级配对混合土体剪切特性影响研究

Effect of rubber-sand mixtures gradation on shear characteristics of mixed soil

为了研究橡胶砂的剪切特性,采用室内大型直剪仪,研究了4种橡胶砂级配(1种间断级配、2种连续级配、1种开级配)、3种橡胶掺入量(10%、30%、60%)、3种竖向应力(30、60、90 kPa)对橡胶砂强度特性和体变特性的影响;并在室内直剪试验的基础上,按照相同级配和橡胶掺量建立纯砂和橡胶砂的离散元数值模型,从颗粒接触状态和颗粒位移角度探讨橡胶砂内在力学机制。研究结果表明:在低橡胶含量下,橡胶砂的剪应力曲线趋势和纯砂一致,但其抗剪强度均低于纯砂;橡胶砂剪切应力随竖向应力的增大而增大,4种级配的橡胶砂中连续级配SR2抗剪强度最高;橡胶颗粒的掺入能有效抑制砂土的剪胀,其中间断级配SR1橡胶砂抑制土体剪胀效果最好,剪胀量相较于纯砂减少了37.6%;橡胶砂的内摩擦角随着橡胶掺入量的增大而减小,同一橡胶掺量下连续级配SR2橡胶砂的内摩擦角最大;橡胶颗粒在橡胶砂力链网络中主要参与弱力链的形成,橡胶砂剪切带宽度小于纯砂的剪切带宽度。

To study the shear characteristics of rubber-sand mixtures,the effects of four rubber-sand mixtures gradations(one type of gap gradation,two types of continuous gradations,and one type of open gradation),three rubber contents(10%,30%,and 60%),and three vertical stresses(30 kPa,60 kPa,and 90 kPa)on the strength characteristics and volumetric change characteristics of rubber-sand mixtures were investigated by using a laboratory large-scale direct shear apparatus;and based on the laboratory direct shear test,the discrete element numerical models of pure sand and rubber-sand mixtures were established according to the same gradation and rubber content.The intrinsic mechanical mechanism of rubber-sand mixtures was explored from the perspective of particle contact state and displacement.The results show that the shear stress curve of rubber-sand mixtures is the same as that of pure sand at low rubber content,but its shear strength is lower than that of pure sand;the shear stress of rubber-sand mixtures increases with the increase of vertical stress,and the shear strength of continuous gradation SR2 is the highest among the four gradations of rubber-sand mixtures;the admixture of rubber particles can effectively inhibit the dilatancy of sandy soil,among which the gap grade SR1 has the best effect on inhibiting soil dilatancy,and the dilatancyis reduced by 37%compared with that of pure sand.The internal friction angle of rubber-sand mixtures decreases with the increase of rubber content,and the internal friction angle of continuous gradation SR2 is the largest under the same rubber content;rubber particles mainly participate in the formation of weak force chain in the rubber-sand mixtures force chain network,and the shear zone width of rubber-sand mixtures is smaller than that of pure sand.