真三轴条件下的原状黄土增湿变形特性

为了研究复杂应力条件下原状黄土的增湿变形特性,利用改进的非饱和土湿陷真三轴仪,在测量吸力条件下对原状黄土进行双线法分级浸水增湿试验,探讨力-水耦合作用下吸力的变化特性,研究真三轴浸水试验的增湿变形特性,以及吸力、净围压、中主应力和应力比对增湿变形的影响。研究结果表明:由ei-lgp压缩曲线确定了非饱和土的屈服点,屈服点之前,曲线的斜率近似相等;屈服点之后,曲线的斜率随着初始吸力的减小而减小,且非饱和土与饱和土的交点随着初始吸力的增大呈右下方移动趋势。等向压缩过程中,吸力随着净平均应力的增加近似呈线性减小趋势,初始吸力越小,吸力减小的速度越慢,且吸力变化量越小。均压分级浸水增湿时,吸力s随着浸水量w的增加而减小,增湿体变evsh随着浸水量w的增加而增大,不同净围压下的evsh-w关系曲线相互有交叉。交叉区域之前,净围压越大,增湿体变越小,而交叉区域之后,净围压越大,增湿体变越大。在同一净围压条件下,浸水量相同时,初始吸力越大,增湿体变越大。真三轴剪切增湿试验中,应力比k、中主应力参数b值和净围压s3皆对增湿变形有一定的影响。当q/p≤1时,增湿变形曲线前段下凹后段上凹,主要表现为体积增湿变形;当q/p>1时,增湿变形曲线只有下凹部分,主要表现为剪切增湿变形。增湿变形曲线的形态取决于k值和b值的不同组合。

Wetting deformation characteristics of intact loess under true triaxial conditions

In order to study the humidification and deformation characteristics of intact loess under complex stress conditions,the double-line grading wetting tests on intact loess under measuring suction were carried out by using collapsing true triaxial apparatus for unsaturated soil.The variation characteristics of suction under the action of coupling stress and water were discussed.The humidification deformation characteristics of true triaxial soaking tests and the effects of suction,net confining pressure,intermediate principal stress and stress ratio on humidification deformation were studied.The results showed that the yield points of unsaturated soil were determined by the ei-lgp compression curves.Before the yield points,the slope of the curves were approximately equal.After the yield points,the slope reduced with the decrease of the initial suction,and the intersection points between unsaturated soil and saturated soil moved to the lower right with the increase of initial suction.In the process of isotropic compression,suction approximately linearly decreased with the increase of net average stress,the smaller the initial suction,the slower the suction decreased and the smaller the variation amount of suction.When grading soaking and humidifying under pressure equalization,suction s decreased with the increase of water immersion w,and the humidification volume strain enlarged with the increase of water immersion w.The evsh-w relationship curves under different net confining pressures intersected with each other.Before the intersection area,the larger the net confining pressure,the smaller the humidification volume strain,and after the intersection area,the larger the net confining pressure,the larger the humidification volume strain.Under the same net confining pressure condition,when the water immersion amount was the same,the larger the initial suction,the larger the humidification volume strain.In the true triaxial shear humidification tests,the stress ratio k,the intermediate principal stress parameter b value and the net confining pressure s3 all had a certain influence on the humidification deformation.When q/p≤1,the front section of the humidification deformation curve was lower concave,and the back section was upper concave,mainly showing volume humidification deformation.When q/p>1,the humidification deformation curve had only the lower concave part,which was mainly characterized by shear humidification deformation.The shape of the humidification deformation curve depended on different combinations of k and b values.