考虑颗粒破碎的堆石料动力变形特性模拟

颗粒破碎是影响堆石料强度和变形特性的重要因素，但目前针对颗粒破碎的模拟研究多在静力荷载条件下。为研究颗粒破碎对小应变条件下堆石料的动力变形特性的影响，采用多个等粒径小球按最密六方排列随机组合模拟不规则形状的堆石颗粒，通过碎片替换法模拟颗粒破碎，研究了花岗岩堆石料不同围压下的动力响应，探索了孔隙率对动弹性模量的影响，分析了振动过程中的颗粒破碎规律及配位数的频率分布。结果表明模拟的骨架曲线与室内试验结果具有较好的一致性，数值模拟可以较好地再现不同围压下堆石料的动力变形特征。在相同围压和动应力条件下，考虑颗粒破碎的试样会产生更多不可恢复的变形，动应变会明显增大，动弹性模量降低。振动过程中集合体的有效配位数会减小，与不考虑颗粒破碎的情况对比，考虑颗粒破碎的试样具有更多的力学不稳定颗粒，有效配位数的降低更显著。颗粒破碎对最大动弹性模量的影响较小，但会加快动模量随动应变增长而衰减的速率。孔隙率小的试样有效配位数高，且受力性能更好。在相同动应力条件下颗粒破碎较少，动弹性模量随动应变的增加而衰减的速率较慢，最大动弹性模量约为大孔隙率试样的1.2倍。最大动弹性模量主要与有效平均主应力和孔隙率相关，Hardin等提出的经验公式可以较好地描述最大动弹性模量与孔隙比和平均有效主应力的关系。该成果有助于认识粗粒料动荷载下的变形规律，为研究动荷载下的颗粒破碎行为提供参考。

Numerical Simulation of Dynamic Deformation Characteristics of Rockfill Materials Considering Particle Crushing

The strength and deformation characteristics of rockfill materials were influenced by particle breakage. However, the studies on particle breakage were mostly under static loading conditions. To investigate the effect of particle crushing on the dynamic characteristics of rockfill materials under small strain conditions, the discrete element method was selected to simulate the dynamic response of granite rockfill materials under different confining pressures. The irregular particle shapes used hexagonal closed packing with different random combinations. The fragment replacement method was selected to simulate particle crushing. The influence of porosity on dynamic elastic modulus was studied, the particle breakage law and the frequency distribution of coordination number during cyclic loading were analyzed. The simulation results were in good agreement with laboratory test results. This indicated that the numerical model could reproduce the dynamic deformation characteristics of rockfill materials under different confining pressures. Particle breakage increased the dynamic strain and decreased dynamic elastic modulus under the same confining pressure and dynamic stress. During cyclic loading, the effective coordination number decreased slowly. The sample with particle breakage produced more mechanically unstable particles, and the decrease of effective coordination number was more significant when compared with the sample without particle crushing. Particle crushing had little effect on the maximum dynamic elastic modulus, but it accelerated the decay rate of the dynamic elastic modulus with dynamic strain increasing. The sample with lower porosity had higher effective coordination number and better mechanical property. Under the same stress condition, the sample with lower porosity had larger maximum dynamic elastic modulus and went through less particle breakage. The dynamic elastic modulus decayed slowly with the dynamic strain increasing. The maximum dynamic elastic modulus for the sample with lower porosity was about 1.2 times of that for the sample with larger porosity. The maximum dynamic elastic modulus was mainly related to the effective average principal stress and porosity. The empirical formula proposed by Hardin could be used to describe the relationship between the maximum dynamic elastic modulus, void ratio and average effective principal stress. The results were helpful to understand the deformation law of coarse granular materials and provided reference for the simulation of particle crushing behavior under cyclic loading.