考虑多晶冰软化特性的弹塑性损伤本构模型开发及应用

Development and application of elastic-plastic damage constitutive model considering softening characteristics of polycrystalline ice

随着全球气候逐渐变暖,冰川、大型冰盖或较厚的冰层发生大规模滑动、崩塌灾害的可能性和危险性不断增加,研究多晶冰的变形特性并建立其本构模型对极地灾害预报具有重要的意义。基于已有的人造多晶冰常规三轴压缩试验数据,发现人造多晶冰具有明显的应变软化特征,构建以等效塑性应变为变量的损伤变量,以摩尔-库仑准则为初始屈服函数,采用相适应流动法则,建立了能够反映多晶冰应变软化特征的弹塑性损伤本构模型。利用不同围压、不同温度条件下的常规三轴压缩试验数据对提出的本构模型进行了验证,并对部分模型参数进行了参数敏感性分析。将建立的弹塑性损伤本构模型写入FLAC软件中,利用单个单元的三轴压缩数值模拟对写入的本构模型进行了验证;然后使用写入的弹塑性损伤本构模型对圆柱状试样开展三轴压缩数值模拟,对数值模拟结果进行了详细的分析。研究结果以期为冰川稳定性分析以及冰川多场耦合研究提供理论及数值基础。

With the gradual warming of the global climate, the possibility of large-scale sliding and collapse disasters of glaciers, large ice sheets or thicker ice layers are increasing. Research on the deformation characteristics of polycrystalline ice and establishing its constitutive model are of great significance for the disaster forecasting of polar regions. Based on the existing triaxial compression test data of artificial polycrystalline ice, it is found that the artificial polycrystalline ice has prominent characteristics of strain softening. The damage variable with equivalent plastic strain as the variable is proposed. By using the Mohr-Coulomb criterion as the initial yield function, and adopting the associated flow rule, an elastoplastic damage constitutive model that can reflect the strain softening characteristics of polycrystalline ice is established. The proposed constitutive model is verified by triaxial compression test data under different confining pressures and different temperatures, and parameter sensitivity analysis of some model parameters is carried out. The established elastoplastic damage constitutive model was written in the FLACsoftware, and the embedded constitutive model was verified by the triaxial compression of a single unit. Then, the embedded elastoplastic damage constitutive model is used to perform triaxial compression on the cylindrical specimen. The simulation results are analyzed in detail. The results provide a theoretical and numerical basis for the stability analysis of glaciers and the multi field coupling study of glaciers.