在宽广吸力范围内对不同吸力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。关于吸力的施加,较低吸力采用轴平移技术;高吸力采用蒸汽平衡法。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大而升高、剪缩量变小,并且随着吸力的增大其偏应力–应变关系和体变明显地表现出类似超固结土的特性。主要原因是试样受到较大的吸力,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。在宽广吸力范围内,吸力所引起弱膨胀性土体积收缩明显,不可忽视。根据压汞试验结果确定的微观饱和度引入有效饱和度中,再将试验结果与修正后的Bishop非饱和土强度公式的预测值进行比较,证明了修正后的Bishop非饱和土强度公式在宽广吸力范围内可较为准确地预测非饱和弱膨胀土的抗剪强度。 A series of suction-controlled triaxial shear tests were performed on unsaturated weakly expansive soils with different suction in a wide suction range. With respect to the application of suction, the lower suction uses the shaft translation technique; the high suction uses the steam balance method. The test results show that under the same net stress, the stress-strain curve of the sample increases with the increase of the suction force and the amount of shear decreases, and the deviatoric stress-strain relationship and body increase with the increase of the suction force. Obviously shows similar properties of over-consolidated soil. The main reason is that the sample is subjected to a large suction force, the water loss shrinkage of the weak expansive soil sample, and the decrease of the void ratio are all obvious, so that the sample exhibits the characteristics similar to the over-consolidated clay in the shearing process. In the broad suction range, the volume shrinkage of weakly expansive soil caused by suction is obvious and cannot be ignored. According to the results of mercury injection test, the micro saturation determined by the mercury injection test results in the effective saturation, and then the test results are compared with the predicted value of the modified Bishop unsaturated soil strength formula. It is proved that the modified Bishop unsaturated soil strength formula is broadly attractive. The shear strength of unsaturated weak expansive soil can be predicted more accurately in the range.