In order to study the effect of void ratio on soil-water characteristics of Nanyang expansive soil in full suction range,the pressure plate method,the filter paper method and the vapor equilibrium technique were carried out.Test results show that the wetting curve of the soil water characteristic curve(SWCC) of Nanyang expansive soil can be effectively measured by the pressure plate method and the vapor equilibrium technique,and the SWCC is approximate to a straight line when suction is beyond the air entry value.The transition zone does not obviously exist.In wetting-drying tests,the swelling and shrinkage deformation of expansive soil is not completely reversible.There is an obvious hysteresis effect with different initial void ratio in the process of wetting and drying.And the hysteresis effect is more obvious with increasing initial void ratio.The SWCC represented by water content with different initial void ratio in the full suction range tend to be consistent with increasing suction.The SWCC represented by degree of saturation in the full suction range moves up with increasing initial void ratio.When water content tends to be zero,the maximum suction of Nanyang expansive soil is less than 1 000 MPa,and its maximum suction is in the range of 500 ～600 MPa.%用压力板法、滤纸法和饱和盐溶液蒸汽平衡法研究了孔隙比对全吸力范围内南阳膨胀土压实样土水特性的影响.试验结果表明:联合压力板法和蒸汽平衡法可以较好地测量出全吸力范围内南阳膨胀土土水特征曲线的脱湿曲线,其土水特征曲线在吸力超过进气值后近似为一条直线,没有明显的过渡段;在干湿循环过程中,膨胀土的胀缩变形并不完全可逆;不同初始孔隙比的试样在脱湿与吸湿过程中均存在明显的滞回效应,并且初始孔隙比越大,反映在土水特征曲线上的滞回效应越明显;全吸力范围内以含水率表示的不同初始孔隙比土水特征曲线随着吸力的增大逐渐趋于一致;全吸力范围内以饱和度表示的土水特征曲线随着初始孔隙比的增大,整体向上移动;当含水率趋于零的时候,南阳膨胀土的吸力小于1 000 MPa,其最大吸力大致在500 ～ 600 MPa.
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