基于UH模型的土体变形局部化分析

Localization of soil deformation depending on UH model

应变局部化现象广泛地存在于超固结土和砂土的室内及现场试验中。当土体发生破坏时,土体变形往往集中在狭窄的带状区域,并且破坏面上的强度并非同时发挥。超固结度、围压、摩擦角、温度及加载应变率等因素的改变均可以使土体强度提高,但上述部分因素在提高土体强度的同时却可能对土体的稳定性产生不利影响,导致土体更易发生局部化破坏。因而基于UH模型(统一硬化模型),采用平面应变下的分叉理论解对土体局部化问题进行分叉分析,探究了超固结度、围压、临界状态应力比、温度及加载应变率对分叉应变影响,并对所得结果进行分析讨论。此外,通过有限差分方法在平面应变条件下对局部化现象进行数值模拟,上述影响因素的分析结果与理论解相一致。

The phenomenon of strain localization widely exists in both laboratory or field tests on over-consolidated clay or sand. The deformation of soils when failure occurs, often localizes in a narrow zone, and the strength of the failure plane cannot be reached at the same time. The overconsolidation ratio, mean pressure, friction angle, temperature and strain rate are the main factors to increase the strength of soils. However, some factors may bring negative influence on soil stablity while increasing the strength of soils. Thus, based on the UH model(unified hardening model), the theoretical solution is used to analyze the phenomenon of bifurcation under plain strain. The impacts of the over-consolidation ratio, mean pressure, critical state ratio, temperature and stain rate on bifurcation strain are systematically studied and further discussed. Same conclusions are drawn in the numerical simulations of stain localization by using the finite differential method under the same condition of plain strain.