非饱和土脱湿与吸湿水力特性对比研究

A study of the hydro-mechanical properties of unsaturated loess under the drying and wetting path

非饱和土水力相互作用特征曲线（土-水特征曲线、渗透系数函数和吸应力特征曲线等）的获取在非饱和土斜坡的渗流和力学分析中有着至关重要的作用。目前,大多数试验方法中最适合确定脱湿状态的是土水特征曲线,但能够反映降雨过后斜坡短期内入渗和径流现象的反而是吸湿状态。基于此,采用瞬态脱湿与吸湿的试验方法 （TRIM）,在短时间内获取该类土脱湿和吸湿条件下全吸力（0~10~6k Pa）范围内的土-水特征曲线、渗透系数函数和吸应力特征曲线,并对其脱湿与吸湿路径下的水力特性、模型参数及滞后特性进行了对比研究。结果表明,土的脱湿过程与吸湿过程的土-水特性明显不同,两种路径下的非饱和渗透系数、进气值、饱和渗透系数等参数均存在差异,而这种差异体现了吸应力的滞后特性,而这种滞后性足以诱发该类土的滑坡。这一研究结果对提高土-水特征曲线参数拟合的精度、提高试验效率及降雨型滑坡灾害的防灾预警具有一定的实用价值。

To determine the soil water characteristic curve（ SWCC）,the hydraulic conductivity function（ HCF） and the suction-stress characteristic curve（ SSCC） play a key role in analyzing the mechanical behavior of unsaturated loess. In general,most experiment methods are most suitable for determining the SWCC under the drying condition. However,the phenomenon of infiltration and runoff in the short term after the rainfall on the slope is better described under the wetting conditions. Based on the transient release and imbibition methods（ TRIM） in a short period of time,the SWCC,HCF and SSCC of soils within the suction（ 0-106 k Pa） under both the drying and wetting conditions can be acquired,and the uniqueness of the results obtained by inverse modeling are verified. The results show that the hydro-mechanical properties of soils under both the drying and wetting conditions are obviously different. Because of the difference in parameters of unsaturated hydraulic conductivity,the air-entry pressures under the two paths are different,resulting in the suction stress due to hysteresis in this soil. At the same time this amount of difference in suction stress issufficient to trigger landslide. Based on these recognitions,the experiment for measuring the SWRC can be designed more efficiently and the curve fitting parameters can be obtained more accurately. The warning criteria of landslide hazards for the specific mitigation purpose are set up.