不排水加载条件下K_0固结饱和砂土失稳预测  

Prediction of instability of K0-consolidated saturated sands under undrained loading conditions

作　　者：吕玺琳[1,2] 钱建固[1,2] 黄茂松[1,2] 

机构地区：[1]同济大学岩土及地下工程教育部重点实验室,上海200092 [2]同济大学地下建筑与工程系,上海200092

出　　处：《岩土工程学报》2015年第6期1010-1015,共6页Chinese Journal of Geotechnical Engineering

基　　金：国家重点基础研究发展计划(973计划)课题(2012CB719803);国家自然科学基金项目(11372228);上海市自然科学基金项目(13ZR1443800)

摘　　要：基于二阶功准则及变形分叉理论,建立了分散性失稳和应变局部化失稳的理论判别准则,对K0固结不排水加载条件下饱和砂土的失稳特性进行了理论研究。分析结果表明,三轴应力状态下,土体表现为分散性失稳模式,应变局部化则不会发生。在试样初始状态较密实的状态下,由于相变作用,土体能够保持稳定,直至达到塑性极限破坏。在平面应变状态下,分散性失稳和应变局部化均可能发生,且分散性失稳先于应变局部化失稳出现。非共轴塑性流动法则的引入对分散性失稳预测结果无影响,然而对应变局部化的预测结果影响较大,且只有在引入了非共轴流动法则的条件下,应变局部化的理论预测结果才能与试验结果一致。Based on the second-order work criterion and bifurcation analysis, the framework for predicting the onset of diffuse instability and strain localization are proposed to study the instability of soils under K0-consolidated undrained loading conditions.The analysis shows that the diffuse instability occurs in triaxial tests while the strain localization does not occur. The onset of diffuse instability relies on the initial void ratio of the specimen, and if the soil is dense enough, the soil specimen keeps stable until plastic limit due to the phase transformation. Under the plane strain conditions, the diffuse instability precedes the strain localization, and with further loading, the diffuse instability transits to strain localization. The inclusion of the non-coaxial plasticity flow rule has significant influence on the onset of strain localization, and the predicted results agree well with the experiments only if the non-coaxial flow rule is considered, while it shows no influence on the prediction of diffuse instability.

关 键 词：砂土 材料状态 分散性失稳 应变局部化 非共轴塑性流动 

分 类 号：TU441[建筑科学—岩土工程]