不同初始状态橡胶砂直剪试验研究

TEST STUDY OF RUBBER-SAND MIXTURES UNDER DIFFERENT INITIAL STATES IN DIRECT SHEAR

橡胶砂是一种具有潜在广泛应用价值的新型环保岩土材料。为研究橡胶砂在干燥击实、干燥未击实及掺水未击实3种不同初始状态下的直剪特征,对试样（橡胶颗粒、砂、橡胶砂）进行了一系列直接剪切试验,考虑了橡胶颗粒含量及竖向压力对其直剪特征的影响。结果表明：1）干燥击实橡胶砂的剪应力-剪切位移曲线随着橡胶含量的增大由软化型逐渐向硬化型转变;且随着橡胶砂密实性的降低,其剪应力-剪切位移曲线越来越多地表现为硬化型;掺水未击实橡胶砂的剪应力-剪切位移曲线均表现为硬化型。2）竖向压力小于50 k Pa且砂粒密实性较低时,橡胶颗粒可改善砂的强度,最优橡胶含量为20%~40%,且对掺水未击实砂的最优橡胶含量约为10%。3）橡胶砂越密实,越易产生剪胀,湿润橡胶砂比干燥橡胶砂越易产生剪缩。4）不同初始状态对橡胶砂的直剪特征如剪应力-剪切位移曲线、抗剪强度包线、竖向位移-剪切位移曲线的影响随橡胶含量的增大而减弱。

Rubber sand mixtures（ RSM） are a new kind of environmentally beneficial geotechnical material with potential wide application value. In order to study direct shear characters of RSM with different rubber contents under different vertical stresses and three different initial states,including sample by drying combined compaction,drying but uncompaction,and watering but uncompaction respectively,a series of direct shear tests were conducted for samples including rubber particles,sand and RSM. The result showed： 1） the shear stress-displacement curves of the sample of drying compaction RSM were changed from softening model to hardening model gradually with the increase of rubber content,and the shear stress-displacement curves of RSM more and more evidently showed hardening characteristic when its density was decreased,all the shear stress-displacement curves of the sample of watering but uncompaction RSM showed hardening property; 2） rubber particles could improve the shear strength of sand whose density was low when vertical pressure was less than 50 k Pa,and the range of the optimal rubber content was 20% ~ 40%,and rubber particles could also improve the direct shear strength of the sample of watering but uncompaction sand,whose optimal rubber content was about 10%; 3） the more denser the RSM,the more easier the shear dilatancy produced,and wet RSM was easier to produce shear contraction than dry RSM; 4） the effect of the different initial states on direct shear characters,such as shear stress-displacement curves,shear strength envelopes and vertical-shear displacement curves of RSM was reduced with the increase of rubber content.