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基于平面应变改造后的西安理工大学真三轴仪,在不同围压条件下对不同含水率黄土进行了侧向卸载平面应变试验,研究了平面应变条件下原状黄土的卸载强度、变形特性以及原状黄土的破坏方式。研究结果表明:不同固结围压条件下,各含水率原状黄土的侧向卸载应力-应变曲线均为硬化型,近似呈理想塑性曲线。剪切过程中,黄土的侧向与竖向变形呈非线性变化,侧向应变的发展要快于竖向应变,体积变形均为体胀。侧向卸载条件下土的破坏应变要比平面应变竖向加载和常规三轴试验小得多。黄土的卸载破坏强度与含水率、围压和球应力状态密切相关;随着含水率的增大,黏聚力衰减明显,内摩擦角略有减小。侧向卸载条件下,原状黄土呈剪胀滑移破坏形式。
Based on the true triaxial apparatus of Xi’an University of Technology after the transformation of plane strain, lateral unloading plane strain tests of loess with different water contents under different confining pressures were carried out. The unloading strength, deformation characteristics and undisturbed characteristics of undisturbed loess under plane strain were studied. Loess destruction way. The results show that under different confining confining pressures, the lateral unloading stress-strain curves of the intact loess with different water contents are all hardened and approximate to the ideal plasticity curve. In the process of shearing, the lateral and vertical deformation of loess show a nonlinear change, the development of lateral strain is faster than the vertical strain, and the volume deformation is both body bulge. Under lateral unloading conditions, the failure strain of soil is much smaller than that of plane strain and vertical triaxial tests. The unloading failure strength of loess is closely related to the moisture content, confining pressure and the state of ball stress. With the increase of water content, the cohesion decay obviously and the internal friction angle slightly decreases. Under the condition of lateral unloading, undisturbed loess showed the form of dilatancy and slip damage.