双轴压缩条件下颗粒材料中力链的演化

Force chain evolution in granular materials during biaxial compression

针对无黏性颗粒材料,开展了柔性边界双轴压缩数值试验,分析了不同围压下力链的数量、方向概率等随轴向应变的变化。研究结果表明:不断加载使得游离的高应力颗粒有所减少,荷载更多的被力链承担;统计意义上,力链最大长度为9个颗粒。轴向±30o范围内力链概率随应变的发展与偏应力一致,而与其邻接的[40o,60o]和[120o,140o]两个方向上的力链概率随应变的发展与偏应力相反;双轴试样剪切破坏时有单剪切带和双剪切带两种模式,当[40o,60o]和[120o,140o]两个角度区间的力链概率有较大差异时,剪切带出现在力链较少的角度区间;当这两个角度区间力链概率接近时,试样中将出现两个剪切带。

Numerical biaxial tests of cohesionless granular materials were conducted using a flexible boundary model to investigate the evolution of the quantity and directional probability of force chains with varied axial strain,under different confining pressures.It has found that the quantity of high-stress particles which don’t form force chains decrease as the deviatoric stress increases,indicating that more loads are born by force chains.Statistically,the maximum length of force chains is 9 particles.As axial strain increases,the probability of force chains oriented in the direction[60o,120o]evolves alike with deviatoric stress.While the probability of force chains oriented in the two directions[40o,60o]and[120o,140o]evolves contrary to deviatoric stress.Two types of shear failure were found in biaxial tests:single shear band and two conjugated shear bands.According to the comparison of the probability of force chains oriented in[40o,60o]and[120o,140o],a single shear band occurs within the angle range with obviously less probability,while two conjugated shear bands occur when the probabilities of force chains in these two directions have slight difference.