结构性黄土应力应变特征分析

Stress-Strain Behavior of the Structured Loess

利用GDS三轴试验系统开展了饱和黄土等压/偏压固结不排水常规三轴压缩试验研究(应变控制式),获得了一组结构性黄土应力～应变关系曲线。此类曲线反映了饱和黄土应力～应变关系具有"暂稳态"特征,其后发生强烈应变软化。此外又开展了应力控制式三轴压缩试验研究,试验结果表明,应力增量式剪切能够最大程度地反映土体微观结构特征,应力失控的拐点即为土体结构强度。而应变增量控制的传统剪切模式,在应变速率精确控制的同时,削弱了其结构性。因此,研究在外界荷载作用下的黄土的力学性状,建议开展应力控制式三轴压缩试验,以获得更为合理的结果。

Loess is a typical structured soil. It is believed that the characteristics of the microstructure and the fabric of the lo- ess could be reflected in its stress-strain relationship. Both conventional strain controlled isotropic and anisotropic consolidation undrained shear testes on undisturbed loess samples were initially conducted by the GDS triaxial testing system. A series of stress-strain relationships on the were obtained. It is observed that a typical stress-strain curve first demonstrated a steady state for a short period of time followed by a strong strain-softening behavior. To further explore the behavior of this structured lo- ess, a series of stress-controlled triaxial compression tests were conducted. It is founded that the stress-controlled triaxial tests had a better characterization of the microstructure of the loess. The structural strength of the soil is observed at the point of stress failure. Whereas, in the conventional strain-controlled triaxial tests, the constant strain rate usually could not capture the structural strength of the loess.