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采用西安理工大学自主研发的真三轴仪,对西安白鹿原黄土进行了不同中主应力比值、不同固结围压的试验研究,探讨了黄土剪切带形成与峰值强度、中主应变与大主应变关系曲线、体应变与大主应变关系曲线特征点之间的联系以及子午平面、p平面上的强度变化规律。分析了真三轴应力条件下黄土强度变形规律和试样剪切带破坏模式和黄土在复杂应力状态下剪切带形成的判断依据和原因,研究表明,真三轴压缩原状黄土具有明显的剪切带,围压和中主应力比值较小时表现为软化,围压和中主应力比值较大时则表现为硬化;中主应变、体应变与大主应变关系曲线较为一致的转折点反映了土变形性状发生变化;与中主应变方向一致的剪切带两侧土结构块体产生相对滑移,剪切带开始形成和发展;土应变曲线的转折点可以作为土固结结构内剪切带形成的判断依据;子午平面上强度线呈线性变化规律,p平面上呈曲边三角形非线性变化规律,并且与3σ-SMP强度准则较为接近。不同应力条件下剪切带变化复杂的破坏模式与黄土原生的结构特征和加载共同作用的变化有密切联系。
Based on the true triaxial apparatus independently developed by Xi’an University of Technology, this paper studied the different ratios of middle principal stress and different confining confining pressure of the Bai Luyuan loess in Xi’an, and discussed the formation and peak strength of the loess shear band, Strain relationship curve, the relationship between the body strain and the main strain curve, as well as the intensity variation of the meridional plane and the p-plane. The deformation law of loess under true triaxial stress and the failure mode of shear band and the judgment basis and reason of loess formation under complex stress state are analyzed. The results show that the true triaxial compression loess has obvious shear strength When the ratio of shear banding, confining pressure and middle principal stress is small, it softens, and when the ratio of confining pressure and middle principal stress is larger, it shows hardening. The turning point of the curve of the main principal strain and the main principal strain is more consistent. The deformation traits change; the relative slip of soil structure blocks on both sides of the shear zone coincides with the direction of the main strain, and the shear zone begins to form and develop; the turning point of the soil strain curve can be formed as the shear zone in the soil consolidation structure . The intensity line in the meridional plane shows a linear variation, and the non-linear variation in the plane of the triangle on the p-plane shows a close relationship with the 3σ-SMP intensity criterion. The complicated failure modes under different stress conditions are closely related to the structural features of the loess and the changes of loading interaction.