离散元表征的级配碎石加州承载比细观力学行为研究

Study on the meso-mechanical behavior of California bearing ratio of graded gravel with discrete element method

基于离散元法构建符合真实级配的石灰石碎石二维细观模型,确定模型的细观参数与加载速率,研究级配碎石的加州承载比(CBR)试验。通过对试验和模拟中贯入力-贯入量曲线以及CBR值进行对比验证,验证模型的合理性与正确性。分析加载后的主应力方向、接触力链和位移矢量等细观机制变化规律。分析加载速率、摩擦因数与刚度比等参数对石灰石碎石CBR值的影响。研究结果表明:随着加载速率的降低,CBR数值基本呈缓慢降低的趋势;集料的纵向变化明显于横向变化,离散元模型能够较好地反映级配碎石的细观作用机制;颗粒间摩擦因数的增加能够明显提高级配碎石的抗压能力,碎石体系的抗变形能力随着法向刚度大小增大而增大。

A two-dimensional discrete element model of a graded gravel material with real graduation is developed based on discrete element software PFC2D to simulate and analyze the California bearing ratio(CBR)of a graded gravel material.The results of the force-penetration value curve and CBR value from the discrete element simulation were compared with actual test results and analyze the error and its source of the numerical model,which validated reasonability of the model.Then,the model was applied to study the micro-mechanism variation rule of the main stress direction,contact force chain and displacement vector of the CBR test of a graded gravel material,e.g.,it also study the effects of various loading speeds,different friction coefficients and stiffness ratio of particles on the CBR of the material.The results indicate that the CBR value decreases slowly with the decrease of loading rate.The longitudinal variation of aggregate is more obvious than the transverse variation,and the discrete element model can better reflect the micro-mechanism of graded aggregates In addition,the increase of friction coefficient between particles cannot obviously improve the compressive ability of the graded gravel and the deformation resistance of gravel system increases with the increase of normal stiffness.