主应力旋转条件下粉细砂的非比例加载变形特性

Non-proportional loading deformation characteristics of silty fine sand under principal stress rotation

对粉细砂进行一系列空心圆柱扭剪试验,研究土体在经历含主应力轴偏转的非比例加载路径时的变形特性,重点分析偏应力水平、中主应力系数对土体变形产生的影响。试验中发现弹性剪应变在总剪应变中所占比例较大。在此基础上重新定义了非共轴角,并对饱和粉细砂的变形特性及其影响因素进行研究。结果表明,纯主应力旋转过程中,不同偏应力比、中主应力系数的土体,广义剪应变的整体发展规律相似,偏应力比与中主应力系数对加载末期的土体应变硬化产生较大影响;偏应力比与广义剪应力相同时,中主应力系数的差异使得土体的各向异性在变形响应中得以体现,从而表现出广义剪应变的差异;主应力旋转将使粉细砂产生明显的塑性变形,相较于中主应力系数,偏应力比对于砂土非共轴变形特性的影响更大。

In order to study the effect of the deviatoric stress ratio and the intermediate principal stress coefficient on the soil deformation under the principal stress rotation,a series of non-proportional loading tests were carried out using the hollow cylinder torsional shear apparatus.It was found that the elastic shear strain accounts for a large proportion of the total shear strain,which could not be ignored.On this basis,the non-coaxial angle was redefined,and the deformation characteristics of saturated silty fine sand and its influencing factors were studied.The results showed that during pure principal stress rotation,the overall development law of generalized shear strain of soils with different deviatoric stress ratio and intermediate principal stress coefficient was very similar.The strain hardening of soil at the end of loading could be affected significantly by the intermediate principal stress coefficient as well as the deviatoric stress ratio.When the deviatoric stress ratio and generalized shear stress of soil were the same,the anisotropy of soil was reflected in the deformation response due to the difference of intermediate principal stress coefficient,which showed the difference of generalized shear strain.The rotation of stress axis caused obvious plastic deformation of fine sand,and the effect of deviator stress ratio on non-coaxial deformation characteristics of sand was greater than that of intermediate principal stress coefficient.