9种土样高吸力下的持水特征

持水特征曲线(SWRC)是非饱和土重要的本构关系。大部分SWRC由轴平移方法获得,其所能控制的吸力范围较小;然而工程实践中相对湿度常低于95%(吸力高于7.1 MPa);因此采用动态露点法测定Wyoming膨润土、宁明膨胀土、荆门黄褐色膨胀土、Denver黏土岩、荆门棕褐色膨胀土、武汉黏土、三门峡粉质黏土、郑州粉土、开封黄河砂相对湿度3%~95%范围的吸脱湿过程SWRC。采用相对湿度95%下吸湿质量含水率w95量化高吸力下持水能力,采用吸脱湿SWRC间滞回区域面积HHA量化高吸力下SWRC滞回效应强弱,采用同一吸力下吸脱湿SWRC含水率之差最大值Δw_max量化水力滞回导致的含水率偏差范围。获得了w95,HHA,Δw_max与液限、塑性指数、阳离子交换量、比表面积等土性参数间的量化关系,建议了w95作为膨胀潜势判别标准并验证其可行性,改进了Fredlund-Xing(1994)模型以描述高吸力下上述9种土样吸脱湿过程SWRC,以期为高吸力下相关土力学工程实践提供依据和参考。

Soil-water retention of 9 kinds of soils under high suctions

The soil-water retention curve(SWRC)is the important constitutive relation of unsaturated soil.Most SWRCs are determined by the axis translation method which is suitable for suctions in the range of 0 to 1.5 MPa.However,the relative humidity is usually less than 95%in engineering practice,which means suctions larger than 7.1 MPa.For this reason,the SWRCs for adsorption(wetting)and desorption(drying)of Wyoming bentonite,Ningming expansive soil,Jingmen yellowish-brown expansive soil,Denver claystone,Jingmen brown expansive soil,Wuhan clay,Sanmenxia silty clay,Zhengzhou silt and Kaifeng sand are determined by the dynamic dewpoint isotherm method under the relative humidity in the range of 3%to 95%(for suctions in the range of 7.1 to 482.9 MPa).w95(gravimetric water content under relative humidity of 95%)is adopted to quantify the soil-water retention capacity.HHA(hydraulic hysteresis area between adsorption branch and desorption branch of SWRCs)is adopted to quantify the magnitude of hydraulic hysteresis.Δw_max(the maximum value of the difference of gravimetric water content between adsorption branch and desorption branch of SWRCs under the same suction)is adopted to quantify the deviation of gravimetric water content caused by hydraulic hysteresis.The quantitative relationships among w95,HHA,Δw_max and liquid limit,plastic index,cation exchange capacity and specific surface area are constituted.w95 is proposed as the criterion for the classification of expansive soils,and its feasibility is verified.The Fredlund and Xing(1994)equation is modified to simulate the adsorption and desorption branches of SWRCs of the above 9 kinds of soils under high suctions satisfactorily.