粗粒土尺寸效应的离散元分析

Discrete element analysis for size effects of coarse-grained soils

在土工试验中,粗粒土的力学性质需要考虑颗粒粒径R和试样尺寸L的影响,而利用离散元软件进行数值模拟时,模拟结果的准确性受到计算规模的影响,而计算规模由特征长度比值L/R控制。利用量纲分析理论,可以得到粗粒土数值模型的微观参数和宏观力学参数之间的相似关系,而影响粗粒土抗剪强度的无量纲参数组中,包含特征长度比值L/R。一系列数值三轴压缩试验表明:当L/R足够大(L/R>40)时,L/R对粗粒土抗剪强度没有影响;当L/R较小(L/R<30)时,由于边界摩擦作用,试样的抗剪强度会随着L/R的变化而有较大改变。文中也对离散元软件PFC2D/3D提供的伺服机制进行了讨论。

In geotechnical tests,particle diameter(R) or sample size(L) accounts for the mechanical properties of coarse-grained soils.Correctness and precision of the results modeled with the discrete element analysis(DEA) is limited by the calculation scale,which is also determined by the characteristic length ratio L/R.Scaling law that describes relationship between micro-parameters and macro-parameters of coarse-grained soils is obtained using dimensional analysis;and it is shown that the shear resistance of coarse-grained soils depends on the characteristic length ratio L/R.A series of numerical triaxial tests are performed;it is shown that the L/R has little effects on the shear resistance when L/R is larger than 40;when L/R is less than 30,the shear resistance will be noticeably affected by L/R because of the effects of the boundary friction.The servo-mechanism provided by PFC2D/3D(Particle Flow Code,ITASCA?)is also discussed.