广义双剪应力准则的一种角隅模型的数值实现及应用

Numerical implementation and applications of a corner model of general twinshear criterion

理论和试验表明广义双剪应力准则比传统的Mohr-Coulomb准则能更准确地表述岩土材料的抗剪强度。然而,现有的大型有限元等数值软件中均没有基于该准则的本构模型。为对Mohr-Coulomb准则进行光滑化而提出的Gudehus-Argyris(G-A)函数,其实是广义双剪应力屈服函数的角隅函数。通过对该角隅函数的研究,构造G-A角隅模型,推导各流动矢量计算表达式;在ABAQUS平台上,采用Fortran语言编制相应的基于完全隐式向后欧拉积分算法的UMAT子程序;将该子程序应用于模拟常规三轴压缩、单轴拉伸和真三轴试验以及一均质路堤稳定性分析中,并与ABAQUS内嵌Mohr-Coulomb模型的结果进行了对比。结果表明,该角隅模型的数值实现方法是完全正确和可靠的,有利于广义双剪应力准则的实际应用,以克服传统的Mohr-Coulomb模型偏于保守的缺陷。

Theory and experiments show that the general twin-shear stress criterion can represent the shear strength of soil and rock more accurately than the conventional Mohr-Coulomb criterion.However,there is no constitutive model based on the general twin-shear stress criterion in the existing large-scale finite element software.The smoothed function proposed by Gudehus-Argyris is essentially a corner model of the general twin-shear stress criterion for removing the sharp edges of the Mohr-Coulomb criterion.On the basis of studying the corner model,a plastic potential function was established,and the expressions of all flow vectors were deduced.In line with the complete implicit backward Euler integration algorithm,the corresponding user material subroutine UMAT was programed using the Fortran language in ABAQUS.The UMAT was applied in numerically modeling the conventional triaxial compression test,the uniaxial tension test and true axial test as well as in analyzing the stability of an embankment,and the modeling results were compared with those by the embedded Mohr-Coulomb model in ABAQUS.It is shown that the numerical implementation approach of the corner model is completely correct and reliable,and is beneficial to the practical application of the general twin-shear stress criterion to overcome the conservative flaw that the conventional Mohr-Coulomb model is prone to.