等吸力三轴剪切试验中非饱和黄土强度变形及水量变化特性

Characteristics of Strength Deformation and Water Volume Change of Unsaturated Loess in Triaxial Shear Tests under Constant Suction

通过饱和原状黄土常规三轴试验和非饱和原状黄土等吸力三轴试验研究吸力和净围压对非饱和黄土强度变形的影响,并用HUANG等、胡冉等和方祥位等提出的土水特征曲线模型分析剪切过程中排水规律。研究结果表明:等吸力下原状土样固结剪切体积变形随净围压增大而增大;等净围压下原状土样固结剪切体积变形量随吸力的增大基本呈减小趋势。pq平面内饱和土CSL线逐渐超过低吸力下非饱和土CSL线,原因在于随着p值增大,相对于非饱和土,饱和土孔隙比越来越小,较小孔隙比对抗剪强度的贡献逐渐大于非饱和土吸力对抗剪强度的贡献。应用固结稳定的数据拟合出HUANG等和胡冉等提出的模型参数,并预测剪切过程中的排水量,发现剪切速率对排水量有影响,这两种模型适用于剪切速率慢,排水充分的情况,而方祥位等提出的模型对不同剪切速率会拟合出不同的参数。

In this paper,the effects of suction and net confining pressure on the strength deformation of unsaturated loess were studied.The main test methods included the conventional triaxial test and triaxial test under constant suction for saturated undisturbed loess and unsaturated undisturbed loess,respectively.Additionally,the soilwater characteristic curve models were used to analyze the drainage law at the shear stage.The results showed that the volumetric deformation during the consolidation and shear stages for undisturbed soil increases with increasing net confining pressure under constant suction;however,it decreases with increasing suction under constant net confining pressure.The CSL line of saturated soil in the pq plane gradually exceeds that of the unsaturated soil under low suction because with the increase in p value,the void ratio of saturated soil becomes smaller compared with that of unsaturated soil and the contribution of smaller void ratio to shear strength is gradually greater than that of unsaturated soil.The parameter models proposed by Huang et al.and Hu et al.were obtained and used to predict the moisture content during the shear stage.The influence of shear rate on the change of moisture content is apparent;therefore,the two models are suitable for the condition with a slow shear rate and full drainage.The parameters of the model proposed by Fang et al.were different with different shear rates.