土袋加筋橡胶砂动力特性试验研究

Experimental study on dynamic properties of soilbag reinforced rubber sand mixture

橡胶砂(RSM)可作为一种廉价耗能材料,用土工袋对其进行加筋可提高强度,改善其作为基底隔震垫层时的整体性。运用大型循环剪切试验装置对土袋加筋橡胶砂(SBRSM)进行循环剪切试验,研究其滞回特性,考察橡胶颗粒含量、竖向压力、应变幅值、填充率、土袋铺设方式等主要因素对动剪模量和阻尼比这2个动力参数的影响规律。结果表明:(1)SBRSM的动剪模量随竖向压力增大呈幂函数增加;随橡胶含量增大而减小,lgG_(d)-RC关系近似为线性;随着应变幅值的增大,lgG_(d)-RC关系曲线的斜率略有降低;(2)在大于1%的应变范围内,SBRSM阻尼比随橡胶含量和应变幅值增大均略呈减小趋势,随竖向压力呈幂函数减小规律;(3)SBRSM动剪模量随填充率减小而降低,阻尼比受填充率影响较小,但更小的填充率使其受竖向压力的影响程度降低;(4)土袋竖向铺设时动剪模量相对水平铺设时更低,而阻尼比相对更高,水平横放与水平纵放的动力特性则相差不大。通过对比分析土袋加筋橡胶砂与未加筋橡胶砂的动力特性,揭示土袋加筋橡胶砂动力变形特性规律。

Rubber sand mixture(RSM)can be used as a cheap energy dissipation material.Reinforcing RSM with soilbags can improve its strength and stability as a base isolator beneath the foundation of structures cushion.A large cyclic shear test device was used to study the hysteresis characteristics of soilbag reinforced rubber sand mixture(SBRSM)under cyclic shear load,and the effects of the main factors such as the mass content of the rubber particles,the vertical pressure,the strain amplitude,the filling ratio of soilbag and the arrangement type of the soilbag on the two dynamic parameters,i.e.,the dynamic shear modulus and the damping ratio,of SBRSM were investigated.The results indicate that:(1)the dynamic shear modulus(G)of SBRSM increases exponentially with the vertical pressure,and decreases with the rubber content(RC)with approximately linear lgG_(d)-RC relationship,and the slope of the lgG_(d)-RC relationship decreases slightly with the strain amplitude increasing.(2)In the strain range greater than 1%,the damping ratio of SBRSM decreases slightly with both of rubber content and strain amplitude,and decreases in power function with the vertical pressure.(3)Gof SBRSM decays with the decrease of filling ratio.Though the damping ratio is less affected by filling ratio of soilbag,a lower filling ratio would reduce the influence of vertical pressure on the damping ratio.(4)Both lowerGand higher damping ratio of SBRSM would be gained when laying soilbags vertically comparing with laying them horizontally,and the horizontal shearing direction affects the dynamic properties of SBRSM little when soilbags are paved horizontally.The mechanisms of dynamic deformation characteristics of SBRSM are revealed by comparison of the dynamic characteristics between SBRSM and RSM without soil bag reinforcement.