单轴冲击载荷下基于塑性细观力学的冻土本构模型研究

Study on Constitutive Model of Frozen Soil Based on Plastic Mesomechanics Under Uniaxial Impact Loading

随着寒区工程建设成为中国基础建设的又一大热点,对于冻土冲击动态力学性能及其本构模型的研究已显得十分必要。不同冻结温度的冻土试样通过采用分离式霍普金森压杆(SHPB)进行了不同应变率下的单轴冲击压缩实验。实验结果表明:冻土的弹性模量随着冻结温度的降低而升高,没有明显的率相关性;冻土的强度随着冻结温度的下降和加载应变率的升高而增大。基于实验结果,采用平均化方法推导了与冻结温度相关的冻土等效弹性常数的表达式。同时,采用基体各向同性化的切线模量法建立了冻土的动态塑性细观力学模型。进而,引入与冻结温度和加载应变率相关的连续损伤演化模型构建了冻土的冲击动态本构模型。相应的模拟结果表明,该模型能够很好地描述冻土的动态力学行为。

With the construction of engineering in cold regions becoming another hot spot of infrastructure construction in China,it is necessary to study the dynamic mechanical properties and constitutive models of frozen soil under impact loading.The uniaxial impact compression experiments under different strain rates are carried out on frozen soil with different freezing temperatures using split-Hopkinson pressure bar(SHPB),and the dynamic stress-strain curves under the corresponding conditions are obtained.The experimental results show that the elastic modulus of frozen soil increases with decreasing freezing temperature,and there is no obvious rate correlation;the strength of frozen soil increases with decreasing freezing temperature and increasing loading strain rate.Based on the experimental results,the expression of the equivalent elastic constants of frozen soil is derived using homogenization theory.Meanwhile,a plastic mesomechanical model of frozen soil is established using the isotropic tangent moduli method.Furthermore,a dynamic constitutive model of frozen soil is constructed by introducing a continuous damage evolution model related to freezing temperature and loading strain rate.The calculated results of the constitutive model agreed well with the measured stress-strain curves,which verifies the rationality and validity of the model.