颗粒形状对砂性土宏细观力学性质的影响

Influence of Particle Shape on the Macroscopic and Mesoscopic Mechanical Properties of Sandy Soil

针对多数关于颗粒形状对砂性土宏细观力学性质的影响研究中存在的两个问题,即采用圆形或多边形颗粒代替土粒的随机不规则形状和对比试验中土粒的体积不相等,基于已有的研究成果,先对天然的硅质粗砂开展了直剪试验,后基于颗粒流离散元分析程序(particle flow code,PFC),采用Clump模块模拟真实砂粒的形状,生成天然砂样的PFC模型,进而对直剪试验进行模拟。设计了基于圆形颗粒的对比试验以揭示颗粒形状对砂性土宏细观力学性质的影响。试验结果表明,颗粒形状只有在较高的法向应力下才可以增加砂性土的剪切峰值强度,当法向应力较低时,不规则形状颗粒组成的砂性土的剪切峰值强度低于圆形颗粒组成的砂性土,且当颗粒间的摩擦作用较弱时会有类似的现象,临界值强度并没有因颗粒形状的不规则而有明显差别。对此结果的细观机理也做了浅析,认为在较低法向应力时,圆形砂性土较大的剪胀角是其剪切峰值强度较大的主要原因。

In view of the two problems in most studies on the influence of particle shape on the macroscopic and mesoscopic mechanical properties of sandy soils,that is,the use of circular or polygonal particles instead of random irregular shapes of soil particles and the unequal volume of soil particles in the comparative test.Based on the existing research results,the direct shear test was first carried out on the natural siliceous coarse sand,and then based on the discrete element program particle flow code(PFC),the Clump module was used to simulate the shape of the real sand particles to generate the PFC model of the natural sand sample,and then simulate the direct shear tests.A comparative experiment based on round particles was designed to reveal the effect of particle shape on the macroscopic and mesoscopic mechanical properties of sandy soil.The test results show that the particle shape can increase the peak shear strength of sandy soil only under higher normal stress.When the normal stress is lower,the peak shear strength of sandy soil composed of irregularly shaped particles is still lower.It is not as good as sandy soil composed of round particles,and when the friction between the particles is weak,there will be a similar phenomenon.The critical value strength is not significantly different due to the irregular shape of the particles.The meso-mechanism of this result has also been analyzed,and it is believed that the larger dilatancy angle of round sandy soil is the main reason for the larger shear peak strength when the normal stress is lower.