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美国在2004年通过NCHRP 1-37A项目提出了用于路基土评估的新的动态回弹模量模型。该模型由于考虑了体应力和偏应力的影响,已得到广泛应用。然而,目前对于该模型的有限元实现均采用基于等效动三轴试验的等效切线模量进行材料点的局部迭代。为克服该实现方法在复杂应力状态下因模型简化带来的偏差,基于广义虎克定律推导了该回弹模量模型的精确一致切线刚度矩阵。通过编写的ABAQUS用户自定义材料子程序(UMAT)对轴压和围压加载情形进行有限元模拟,发现新推导的有限元实现方法较现有基于等效三轴试验的简化方法具有更高的计算效率和精度。最后对典型沥青路面结构的分析表明,为提高复杂应力状态下路基响应计算精度,在路面结构分析中采用基于当前应力状态的一致切线刚度矩阵代替等效切线刚度矩阵是十分必要的。
The United States proposed a new dynamic resilience modulus model for subgrade soil assessment through the NCHRP 1-37A project in 2004. The model has been widely used due to the influence of body stress and deviatoric stress. However, for the finite element realization of the present model, the local iteration of the material point is based on the equivalent tangent modulus based on the equivalent dynamic triaxial test. In order to overcome the deviation caused by the simplification of the model under complex stress conditions, the exact consistent tangent stiffness matrix of the elastic modulus model was derived based on the generalized Hooke's law. Finite element simulation of axial compression and confining pressure loading by ABAQUS user-defined material subroutine (UMAT) was performed and found that the newly derived finite element method has a higher performance than the existing simplified method based on equivalent triaxial test Calculate efficiency and accuracy. Finally, the analysis of typical asphalt pavement structure shows that it is necessary to replace the equivalent tangent stiffness matrix with a uniform tangent stiffness matrix based on the current stress state in pavement structure analysis in order to improve the calculation accuracy of roadbed response under complicated stress conditions.