为获得压实膨胀土在湿度与密度变化范围内的抗剪强度全貌，采用非饱和直剪试验测定38种湿度与密度组合状态下荆门弱膨胀土的抗剪强度，获得了湿度从风干到饱和、密度在孔隙比0.539~1.089范围内的抗剪强度的分布规律。结果表明，（1）剪切过程中试样大多呈应变软化，仅在低密度与高湿度组合下产生应变强化。高密度与低湿度组合下易出现“应力跌落”。相同密度下，随湿度增大，土体塑性变形能力增强。相同湿度下，随密度降低，土体塑性变形能力增强；（2）非饱和抗剪强度与总黏聚力均随湿度增加先增大后减小而呈现出显著的“山峰效应”；（3）非饱和抗剪强度、总黏聚力、总内摩擦角均随密度减小而显著降低，呈现出显著的“密度效应”。

To investigate unsaturated shear strength of compacted expansive soil within the entire range of moisture and density state, the unsaturated direct shear tests are conducted on Jingmen expansive soil associated with 38 types of moisture and density state combinations. The distribution of shear strength are obtained with respect to moisture state varying from air-dry to saturation and density represented by void ratio ranging from 0.539 to 1.089. Conclusions are as follows: (1) Strain-softening phenomenon is observed in shear for most samples. In contrast, strain-hardening phenomenon is observed in shear only for the lower-density and higher-moisture state combination. Stress plummeting phenomenon is observed in shear for the higher-density and lower-moisture state combination. Plastic deformation capacity of the soil samples is improved by increasing moisture under the same density or improved by decreasing density under the same moisture. (2) With the moisture increasing from air-dry to saturation, the unsaturated shear strength and total cohesion increase and then decrease, which can be called the peak effect. (3) Unsaturated shear strength, total cohesion, and total friction angle all decrease with decreasing density, which can be called the density effect.