饱和砂土不同应力路径下强度及剪胀真三轴试验研究

Research on Strength and Shear Dilation True Triaxial Test of Saturated Sand Under Different Stress Paths

采用全自动加载真三轴仪对饱和砂土在大主应力方向与沉积方向平行的条件下,在不同固结压力(围压)50kPa、100kPa、200kPa条件下,针对不同应力路径b值取0,0.25,0.5,0.75,1进行真三轴固结排水剪切试验。结果表明:大主应变和偏应力、大主应变和应力比、大主应变和有效应力比的关系基本上表现为光滑的硬化型、理想塑性。个别出现软化型的曲线,软化趋势很弱。在剪切过程中,随剪应力逐渐上升,变形模量逐渐上升,剪切强度也逐渐提高。b=1时曲线界于b=0.5~0.75时的曲线之间。中主应力系数在0.75左右时,曲线斜率达到峰值,且是不同中主应力系数曲线族中的最大值。在中主应力系数b处于区间0~0.5时,b值上升,饱和砂土剪胀性表现越来越显著;在b处于区间0.5~1时,剪胀呈现弱化趋势。整体上对比来看,饱和砂土剪胀特性在高围压状态下不同b值的剪胀性差异更加明显。

A true triaxial consolidation drainage shear test was conducted on saturated sand under different consolidation pressures(confining pressures)of 50kPa,100kPa,and 200kPa,with values of b taken for different stress paths(0,0.25,0.5,0.75,1),under conditions where the direction of major principal stress is parallel to the direction of sand deposition.The results show that the relationship between large principal strain and deviatoric stress,large principal strain and stress ratio,and large principal strain and effective stress ratio is basically characterized by smooth hardening and ideal plasticity.Individual softening curves appear,with a weak softening trend.During the shearing process,as the shear stress gradually increases,the deformation modulus gradually increases,and the shear strength also gradually increases.The curve at b=1 is bounded between the curves at b=0.5~0.75.When the principal stress coefficient is around 0.75,the slope of the curve reaches its peak and is the highest value among different families of principal stress coefficient curves.When the principal stress coefficient b is in the range of 0~0.5,As the b-value increases,the shear dilation performance of saturated sand becomes more and more significant;When b is in the range of 0.5~1,the shear dilation shows a weakening trend.Overall,by comparison,the difference in shear dilation characteristics of saturated sand with different b-values under high confining pressure is more significant.