| 摘要: |
| 【目的】分析动荷载条件下黄土局部化变形的判断依据和剪切带的特性，探究不同初始应力条件对非饱和黄土剪切带特性的影响。【方法】用动扭剪仪进行陕西杨凌非饱和黄土的动变形试验，分析其动本构关系曲线、动孔隙气压力和阻尼比的变化规律，探讨初始平均主应力和初始主应力方向角对剪切带倾角的影响。【结果】土样的动本构关系曲线、动孔隙气压力随时间变化曲线和阻尼比随动剪应变变化曲线皆为非线性型，其变化规律很好地体现了局部化变形的过程。当初始主应力方向角<45°时，土样的剪切带倾角随着初始平均主应力的增加而呈增加趋势；当初始主应力方向角≥45°时，剪切带倾角随着初始平均主应力的增加呈减小趋势。在初始主应力方向角<45°时，剪切带倾角随着初始主应力方向角的增大而减小；当主应力方向角为90°时，土样未出现剪切带。【结论】动荷载作用下，黄土会发生局部化变形，这种局部化变形的出现和发展可以用动孔隙气压力和阻尼比的变化规律来判别，该判别方法意义明确且合理可行；初始平均主应力、初始主应力方向角对黄土的剪切带倾角有一定影响。 |
| 关键词: 黄土 动力特性 动变形 初始主应力方向角 剪切带 |
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| 基金项目:国家自然科学基金项目（50578134）；教育部新世纪优秀人才支持计划项目（NECT-06-0864） |
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| Characteristics of shear bands in loess under test of dynamic deformation |
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| Abstract: |
| 【Objective】Localized deformation of loess under dynamic load has been studied to find the judgment basis for appearing of localized deformation and to analyze the characterristics of shear band in loess.At the same time,the effect of different initial stress state on the properties of shear band has been studied.【Method】Test of dynamic deformation were conducted by a hollow torsional cyclic load triaxial apparatus to study the change law of dynamic constitutive relationship curve,dynamic pore air pressure,damping ratio,and analyze the influence of initial angle of principal stress and average initial principal stress on angle of shear band in loess.【Result】The dynamic constitutive relationship curve,the time-travel of dynamic pore air pressure curve,and the curve of dynamic damping ratio with shear strain change of sample have a variation feature of nonlinear which describes the process of localized deformation well.The results show that the angle of shear band has an increasing trend,as the average initial principal stress increases when initial angle of principal stress is less than 45° and decreases as the average initial principal stress increases when initial angle of principal stress is more than 45°.The angle of shear band decreases when initial angle of principal stress increases from 0° to 45°,and when initial angle of principal stress is equal to 90°,there is no shear band in specimen.【Conclusion】Localized deformation of loess would happen under dynamic load.It is reasonable and feasible to use the time travel of dynamic pore air pressure curve,and the curve of dynamic damping ratio with shear strain change to judge the appearance and development of localized deformation in loess.Initial stress state has a definite influence on the angle of shear band. |
| Key words: loess dynamic characteristics dynamic deformation initial angle of principal stress shear band |
