中文摘要：

为探讨水力路径对膨胀土土水特征与体变特征影响中的滞回效应，以压实度为90％的荆门弱膨胀土为研究对象，采用轴平移技术和等压湿度控制法，开展了控制吸力条件下的脱、吸湿试验，获得了0-391000kPa吸力范围内的孔隙比一含水率一吸力关系的滞回效应规律，结论如下：（1）重力含水率一吸力关系的滞回效应显著。吸力小于10000kPa的区域，脱湿边界线与吸湿边界线间涵盖了较大范围；吸力大于10000kPa的区域，滞回效应弱化。脱湿与吸湿边界线并不平行，前者拐点处的斜率明显大于吸湿边界线的相应值。Fredlund—Xing模型能够很好描述土水特征的脱湿与吸湿边界线。脱、吸湿边界线均可分别通过2个特征点划分为：边界效应区、过渡区与残余区；残余吸力与进水值均可取为359100kPa；进气值为72kPa；出气值为lOkPa。（2）孔隙比一吸力关系呈现出显著的滞回效应。利用3参数指数函数可以很好地分别描述主脱、吸湿路径下的孔隙比一吸力关系。（3）孔隙比一重力含水率关系的滞回效应并不显著。采用2参数指数函数可较好地统一描述不同水力路径下的孔隙比一重力含水率关系。（4）饱和度一吸力关系呈现出显著的滞回效应，其脱、吸湿边界线也可用Fredlund—Xing模型分别描述。（5）体变特征的脱湿速率效应显著。

英文摘要：

The hysteresis effects of hydraulic path on the void ratio-water content-suction behavior of com- pacted expansive soil was investigated experimentally. To this end, a series of suction-controlled drying and wetting tests were carried out on Jingmen compacted expansive soil by both axis translation and isopiestic humidity control techniques, over the range of suction from 0kPa to 391 000kPa. The test results suggest the following observations. （1）Significant hydraulic hysteresis effect on the gravimetric water content-suction relationship is observed, which shows that the main hysteretic loop consists of the main drying and wetting curves surrounds a large area. The main drying curve is not parallel with the main wetting curve, and the slope of the main drying curve at its inflection point is significantly greater than that of the main wetting curve. Each of the two curves can be divided into the boundary-effect zone, transition zone, and residual zone. The residual suction （water-entry value）, air-entry and air expulsion values are estimated as 359100 kPa, 72kPa, and 10kPa, respectively. The Fredlund-Xing equation can fit the main drying and wetting curves over the range of suction from OkPa to 106kPa satisfactorily. （2）The hydraulic hysteresis effect is al- so apparent in the void ratio-suction relationship, which can be described by the three-parameters exponen- tial function. （3）The relationship betwee~ the void ratio and gravimetric water content does not display hys- teresis effect, which under either wetting or drying path can be fitted by a two-parameters exponential func- tion. （4） Apparent hysteresis exists in the relationship between the degree of saturation and suction. The main drying and wetting curves denoted the degree of saturation versus suction can be likewise fitted by Fredlund-Xing equation. （5）The drying rate has significant effect on the volume change behavior of the compacted expansive soil.