中主应力对击实黄土强度和变形特性的影响

Effect of Intermediate Principal Stress on Strength and Deformation Characteristics of Compacted Loess

为研究中主应力对击实黄土强度和变形特性的影响,利用空心圆柱扭剪仪对击实黄土进行主应力轴方向为0°的定向剪切试验,重点探讨中主应力系数b对剪切过程中击实黄土强度和变形的影响。试验结果表明,在不同中主应力系数下试样的广义剪应力-应变曲线发展模式基本相同,其曲线差异不显著,剪切后期试样表现出显著的延性特性。中主应力对击实黄土的强度影响较大,b=0.25时归一化强度最大,而b=0.5时最小。当b从0到0.25时强度增加;当b=0.25时强度达到峰值,随着b的继续增加,强度迅速减小;当b=0.5时强度达到最小值,随着b的进一步增加,强度先增大后减小。随着中主应力系数b的增加,击实黄土的有效内摩擦角呈现增大的趋势,强度参数在b=0时最小,b=0.75时最大,b=1(三轴拉伸)高于b=0(三轴压缩)。

To study the impact of intermediate principal stress on the strength and deformation behavior of compacted loess,a series of tests with the principal stress orientation angle fixed at 0°were carried out using a hollow cylinder apparatus（HCA）.The impact of the intermediate principal stress coefficient b on the strength and deformation of compacted loess is discussed.Test results revealed that at different intermediate principal stress coefficients,the developed models of generalized shear stress-strain curves were basically the same.The generalized shear stress-strain curves were not significantly different and the specimens showed significant ductility during the late stages of shear.The intermediate principal stress significantly affected the strength of the compacted loess.The normalized maximum strength was at b=0.25 and the minimum at b=0.5.The strength increased with b from 0to 0.25.The strength was at its peak when b=0.25,then decreased rapidly as b increased further.The minimum strength reached was when b=0.5,the strength first increased,then decreased as b increased further.With the increase in the intermediate principal stress coefficient,the effective internal friction angle of the compacted loess showed a tendency to increase.The strength parameter was at a minimum when b=0,a maximum when b=0.75,and was greater in b=1（triaxial tension）than b=0（triaxial compression）.