对经历较广吸力范围内不同吸力历史的非饱和弱膨胀土进行了一系列吸力控制的三轴剪切试验。关于最大吸力的施加,高吸力采用蒸汽平衡法;较低吸力采用轴平移技术。试验结果表明:在净应力和吸力相同条件下,经过湿化试样的应力-应变关系曲线升高、剪缩体变小;经过高吸力试样的应力-应变关系曲线也升高、剪缩体变小,随着经历过最大吸力的增加其应力比-应变关系、体变表现出的超固结土特性明显。其主要原因是前期试样受过较大的吸力,相当于受过较大前期固结压力,同时弱膨胀土失水收缩性明显,经过较大吸力后试样孔隙比明显减小,使试样剪切过程中表现出超固结黏土的特性。因此,讨论非饱和弱膨胀性土的应力-应变关系和强度时需考虑吸力历史引起的体积收缩影响。 A series of suction controlled triaxial shear tests were conducted on unsaturated weak expansive soils that experienced different suction history over a wide range of suction. Regarding the application of maximum suction, the high suction adopts the steam balance method; the lower suction adopts the axial shift technique. The results show that under the same conditions of net stress and suction, the stress-strain curve of the wetted specimen increases and the shear-shrinking body becomes smaller. The stress-strain curve of the sample after the high suction increases, The body becomes smaller, with the increase of its maximum stress-stress-strain relationship, the body deformation shows the characteristic of overconsolidated soil is obvious. The main reason for this is that the pre-sample has been subjected to a relatively large suction force, which is equivalent to being subjected to a large pre-consolidation pressure. At the same time, the water-shrinkable property of the weakly expansive soil is conspicuous. After a large suction, the void ratio of the sample is obviously reduced, The process of cutting shows the characteristics of overconsolidated clay. Therefore, when considering the stress-strain relationship and strength of unsaturated weak expansive soil, the influence of volume shrinkage caused by suction history should be considered.