基于橡胶颗粒−砂混合物新型路基填料液化特性

Liquefaction characteristics of new subgrade filler composed of granulated rubber-sand mixtures

为研究橡胶颗粒−砂混合物这种新型路基填料的液化特性,进行室内固结不排水动三轴试验,分析橡胶颗粒体积分数、围压、循环应力比以及加载频率等因素对橡胶颗粒−砂混合物动孔隙水压力特性以及抗液化能力的影响。基于柔性橡胶颗粒与刚性砂颗粒受力特性,分析橡胶颗粒提高饱和砂土抗液化强度的作用机理。研究结果表明:橡胶颗粒−砂混合物的动孔隙水压力发展曲线可以分为3个阶段,即快速增长阶段(初期动孔隙水压力呈不规则增长趋势,后期呈正弦波形式快速增长趋势)、呈正弦波形式缓慢增长阶段以及稳定阶段。加入橡胶颗粒显著提高饱和砂土的抗液化强度,并且随着橡胶颗粒体积分数增大,混合物的抗液化强度提高得更加明显;柔性橡胶颗粒在外荷载作用下能够产生较大的压缩变形而承担一部分外荷载,减小孔隙变形程度,在一定程度上抑制动孔隙水压力的产生和累积,进而提高混合物的抗液化强度;较大围压、较小循环应力比以及较小加载频率都有益于提高橡胶颗粒−砂混合物抗液化强度;橡胶颗粒−砂混合物的归一化动孔隙水压力与振次比的关系曲线符合A型动孔隙水压力曲线模型;本文所用材料的最优橡胶颗粒体积分数在10%左右,此时混合物的静力学强度不低于纯净砂土的静力学强度,并且加入橡胶颗粒可以有效提高饱和砂土的抗液化能力,改善其动力特性。

In order to study the liquefaction characteristics of granulated rubber-sand mixtures,a new type of subgrade filler,the consolidated undrained dynamic triaxial test was carried out.The influences of granulated rubber volume fraction,confining pressure,cyclic stress ratio and loading frequency on dynamic pore water pressure characteristics and liquefaction resistance of the granulated rubber-sand mixtures were analyzed.Based on the mechanical properties of flexible rubber particles and rigid sand particles,the mechanism of the granulated rubber improving the liquefaction resistance of saturated sand was analyzed.The results show that the evolution curves for the dynamic pore water pressure can be divided into three stages:rapid growth stage(dynamic pore water pressure shows an irregular growth trend in early stage and a rapid growth trend in the form of sine wave in later stage),slow growth stage in the form of sine wave and stable stage.The addition of granulated rubber significantly increases the liquefaction resistance of saturated sand,and with the increase of granulated rubber volume fraction,the liquefaction resistance of the mixtures increases more obviously.The flexible rubber particles can produce large compression deformation under the action of external load and bear part of external load,which can reduce the deformation of pore and inhibit the generation and accumulation of the dynamic pore water pressure,and thus the liquefaction resistance of the mixtures will be improved.The larger confining pressure,the smaller cyclic stress ratio and the smaller loading frequency are beneficial to improve the liquefaction resistance of the mixtures.The relationship between the normalized dynamic pore water pressure and the cyclic number ratio of the granulated rubber-sand mixtures conforms with the A-type dynamic pore water pressure model.The optimum rubber volume fraction of the materials used is about 10%.The static strength of the mixtures with 10%rubber volume fraction is not lower than that of the pure sand,and the addition of rubber particles can effectively improve the liquefaction resistance of saturated sand.