中高应变率下钙质砂单颗粒破碎试验与FDM-DEM数值模拟研究

Study on the Breaking Test and FDM-DEM Numerical Simulation of Single Particles of Calcareous Sand Under Medium to High Strain Rates

钙质砂作为岛礁基础设施建设中重要的珊瑚礁岩土材料,常面临飞机起降、波浪流等动力冲击荷载的影响.为了探究钙质砂在中高应变率下的冲击动力学特性,通过开展一维微型霍普金森压杆(SHPB)单颗粒冲击试验,建立有限差分-离散元耦合(FDM-DEM)的数值模型,研究了中高应变率下钙质砂单颗粒宏观冲击特性和微观破碎机理.结果表明,随着应变率从10^(3) s^(-1)提高到10^(4) s^(-1),代表断键开始的相对时间从93%先下降到59%,又上升到78%,裂纹扩展的开始时间先提前后延后;代表相对断键时程的相对时间从7%先上升到63%,又下降到31%,裂纹扩展速度先减缓后加快.此外,当颗粒出现应力峰值时,其破碎程度显著增加;颗粒在破碎前的压缩量增加,表现出一种阻止颗粒进一步破碎的黏滞性.

Calcareous sand,an essential material for coral reef soil in island reef infrastructure construction,is often subjected to dynamic impact loads such as ship collisions and wave currents.To investigate the dynamic impact characteristics of calcareous sand at medium to high strain rates,one-dimensional microscale SHPB single-particle impact tests were conducted.A numerical model combining FDM-DEM was developed to study both the macroscopic impact characteristics and the microscopic fracture mechanisms of calcareous single particles at these strain rates.The results show that as the strain rate increases from 10^(3) s^(-1) to 10^(4) s^(-1),the relative time for particle breakage initiation decreases from 93%to 59%,then rises to 78%,while the initiation time for crack propagation initially advances and then delays.Additionally,the relative duration of fractures increases from 7%to 63%initially and then decreases to 31%,with the crack propagation velocity initially slowing and then accelerating.When the particle reaches its stress peak,fragmentation significantly increases,and the pre-fragmentation compression rises,exhibiting a viscosity that hinders further fragmentation.