岩土材料局部化变形分岔分析

BIFURCATION ANALYSIS ON DEFORMATION LOCALIZATION OF GEOMATERIAL

分析岩土材料和工程中分岔现象,探讨了这些分岔行为产生的机理。详细介绍数学、力学结构以及岩土材料局部化变形分岔分析理论,指出目前的分析方法无法分析岩土失稳过程中剪切带由韧性逐渐转化为脆性,最后发生破坏的过程。应用塑性可膨胀本构关系,结合对称性群论方法和反对称变形分岔分析的初步模拟结果表明:此方法存在一定的局限性。初步提出基于Desai的扰动态概念模型建立的损伤本构关系,进行峰后分岔分析以及率相关和动态加卸载过程分岔的分析。

The bifurcation phenomena, such as shear bands in geological structures, branching behaviors in rock tests and instability in geotechnical engineering, are described and some corresponding mechanisms are discussed. The theories widely applied in bifurcation analysis of localization in mathematics, structural mechanics analysis and geomaterial deformation are presented in detail. The processes for shear bands in loaded geomaterial to deform from toughness to brittleness, and then to lead to fracture of specimens, can not be well imitated by existing analysis methods. The plastic dilatable constitutive relationship together with symmetric group theories and asymmetric bifurcation analysis method are involved in the preliminary analysis. However, their effects are limited. The disturbed state concept proposed by Desai is introduced as a valuable way for the bifurcation analysis of material at the post-peak, with loading rate dependency, and under dynamic loading.