碾压混凝土HJC动态本构模型修正及数值验证

研究高应变率冲击爆炸荷载作用下水工碾压混凝土大坝结构的动力响应,离不开对筑坝材料动态力学特性和本构关系的深入认识。参考实际水工混凝土大坝筑坝材料的配合比和施工方式,制备碾压混凝土试样,分别开展了静态压缩试验和分离式霍普金森压杆(SHPB)试验,以探求碾压混凝土的动态力学特性。基于静、动态力学试验结果,对目前多用于描述混凝土类材料高应变率下力学行为的HJC模型的强度面、应变率增强效应和破坏准则进行了修正,并利用有限元计算手段,建立SHPB试验的数值模型,以验证修正HJC模型的有效性。结果表明:碾压混凝土在高应变率冲击荷载下的动态力学特性表现出明显的应变率效应,动态压缩强度随应变率增加而提高,且与试样尺寸有关。基于试验数据的改进HJC模型有效预测了碾压混凝土在高应变率冲击荷载作用下的动态力学行为,数值计算得到的重构应力--应变曲线基本与SHPB试验结果吻合,采用最大主应变失效准则模拟得到了与SHPB试验加载过程中接近的试样损伤破坏模式,研究成果可用于碾压混凝土结构的抗冲击爆炸设计中。

Modification of a dynamic constitutive model-HJC model for roller-compacted concrete and numerical verification

It is necessary to understand the dynamic mechanical behaviors and constitutive relations of dam materials in studying the dynamic response of hydraulic roller-compacted concrete(RCC)dam withstand high strain rate loads of impact and explosion.Referring to the mix proportion and the construction method of practical hydraulic concrete dam,RCC specimens were prepared and static compression test and split Hopkinson pressure bar(SHPB)test were conducted to explore the dynamic mechanics of RCC.The HJC model which has been widely used to describe the mechanical behavior of concrete under high strain rate was modified including strength surface,strain rate strengthening effect and failure criterion based on the static and dynamic mechanical test results of RCC.Then SHPB experiment was simulated via the finite element method to verify the effectiveness of modified HJC model.The results demonstrate that the dynamic mechanical properties of RCC under high strain rate impact loading show obvious strain rate effect,the dynamic compressive strength increases with strain rate and is related to the specimen size.The reconstructed stress-strain curve obtained by the numerical simulation matches the SHPB test and the maximum principal strain failure criterion can describe the damage process of RCC specimen during SHPB tests well,so that the improved HJC model basing on test data can predict the dynamic mechanical behavior of RCC under high strain rate loading.The research findings can be used in the anti-impact and explosion design of RCC structures.