吸力对弱膨胀土应力应变关系和强度的影响

Effect of suction on stress-strain relationship and strength of weakly expansive soils

本文对不同吸力的南阳弱膨胀土进行了一系列吸力控制的三轴剪切试验。试验结果表明:在净应力相同的条件下,试样的应力应变关系曲线随着吸力的增加而升高、剪缩体变小,并且随着吸力的增加其应力比-应变关系与强度、体变表现出类似超固结土的特性明显。其主要原因是试样受到较大的吸力,有效应力增加,弱膨胀土试样失水收缩、孔隙比减小均明显,使试样剪切过程中表现出类似超固结黏土的特性。吸力所引起弱膨胀性土体积收缩明显,不可忽视。因此预测非饱和弱膨胀性土的应力应变关系和强度特性需考虑吸力所引起的体积收缩影响。

In this paper,a series of suction-controlled triaxial tests were conducted on unsaturated weaklyexpansive soil experiencing different suctions. The test results show that at the same of net stress,the spec-imen experiencing larger suction shows a higher relationship of stress-strain,higher strength and small con-tractive volumetric strain during the shearing,and its relationship of stress-strain,strength and volumetricstrain behavior become more and more similar to the deformation characteristics of overconsolidated soilwith increasing the imposed suction. The reason of the above phenomenon is that the specimen experienceda larger suction,effective stress increases and the weakly expansive soil shrink significantly duo to loss ofwater,and its void ratio reduced obviously,thus the specimen exhibits the strength and deformation charac-teristics of overconsolidated soil during the shearing. The volume shrinkage of weak expansive soil is signifi-cant caused by suction,and it cannot be ignored. Therefore,in order to identify the stress-strain relation-ship and strength characteristics of unsaturated weakly expansive soil,the specimen volume change causedby suction should be considered.