统一硬化模型在FLAC3D中的开发及实现

DEVELOPMENT AND IMPLEMENTATION OF UNIFIED HARDENING MODEL IN FLAC3D

统一硬化模型(UH模型)能够描述超固结土的硬化、软化、剪胀和剪缩等应力-应变特性以及应力历史对土的影响。基于增量弹-塑性模型的基本假设,根据一元二次方程的解法,推导出塑性因子的表达式,由变换应力公式推得变换应力增量与真实应力增量的关系,进而得到UH模型在FLAC3D中的计算格式。基于FLAC3D软件提供的二次开发平台UDM,利用Visual C++编译得到动态链接库文件(.DLL),实现了自定义UH本构模型的开发。通过在不同应力路径下数值解与理论解的对比,验证了UH模型的FLAC3D计算格式的正确性。通过与FLAC3D内置的修正剑桥模型对比,清晰地反映出UH模型在反映土体剪胀、软化、加卸载等方面的优越性。最后,对FLAC3D中非关联流动法则模型的优点进行了讨论。

The over-consolidated unified hardening model （UH model） proposed by Yao et al can describe many characteristics of over-consolidated clays well, including stress-strain relationships, stress dilataney, strain hardening and softening, and stress history dependency. Based on the assumption of elastic-plastic model and solution of a quadratic equation, the computational scheme of UH model in FLAC3D was derived. According to the secondary developing platform, the UH model was developed in FLAC3D with Visual C ＋ ＋ environment. Using that program, numerical simulations of triaxial compression, triaxial extension and plane strain tests were performed, which showed a good agreement with the analytic solution; Compared with the modified Cam-clay model, UH model had several advantages in stress dilatancy, strain softening, loading and unloading features. Finally, the advantage of using constructive models with nonassociated flow rule in FLAC3D was discussed.