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、 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， 平面上呈曲边三角形非线性变化规律，并且与 -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。

Presented herein is an experimental analysis result of Xi’an Bailu Tableland loess tested by true triaxial apparatus, developed by Xi’an University of Technology, with the different consolidation pressures and intermediate principal stress parameters. The occurrence of loess shear band in cubical specimen may be related to its peak strength or the process of hardening regime. Some characteristic changes of the intermediate principal strain and volume change, and strength law on the meridian plane and octahedral plane have also been explored by the measured results of true triaxial tests. Strength, failure strains and the shear failure model of loess specimens have been analyzed to investigate the judgment basis of shear band occurrence under the condition of complex stresses. The results show that the obvious shear band appear in the loess specimens under true triaxial principal stresses, the softening behavior of intact loess occurs under the smaller confining pressure and intermediate principal stress parameters; and the hardening behavior occurs under the larger confining pressure and intermediate principal stress parameters. Consistent turning points on the curve of the intermediate principal strain and volume change with large principal strain indicate the behavior of deformation changing. Structural soil mass in the side of shear band, which is responding to the intermediate principal strain turning point, has a relative sliding and development of shear band. The strength line on meridian plane is linear; and the strength curve on the octahedral plane is a curved-edge-triangle shape that approaches to -SMP strength criterion. The complex changing of shear band of failure pattern is relating to the structural characteristic of natural loess and loading condition of different stresses.