考虑温度效应的延安新区压实黄土全吸力范围持水和渗透特性研究

INVESTIGATION ON WATER RETENTION AND PERMEABILITY CHARACTERISTICS OF YAN'AN COMPACTED LOESS IN A FULL SUCTION RANGE INCORPORATING TEMPERATURE EFFECTS

干旱和半干旱黄土地区的压实土路基、垃圾填埋场黄土盖层等的持水特性和渗透特性均受温度影响。为了探究温度对全吸力范围内压实黄土水力特性的影响规律和内在机制,基于滤纸法和自行研发的小土柱试验装置对不同温度下延安新区压实黄土的土-水特征曲线(SWCC)以及渗透性曲线(HCC)进行测定。结果表明:在黄土SWCC的高吸力段体积含水率随温度升高而减小,低吸力段受温度影响不明显;黄土渗透曲线则是在低吸力段受温度影响显著,温度越高渗透性越强,当土体吸力增大或体积含水率减小至一定值后,温度对土体渗透性的影响可忽略不计。基于此结果,将改进的van Genuchten(VG)模型作为可考虑温度影响的SWCC预测函数,通过拟合实测数据得出温度相关参数并进行验证;对于渗透性曲线,以90 kPa基质吸力为分段点,在低吸力段和高吸力段分别采用统计模型和幂函数进行分段预测,能够得到与实测数据吻合较好的预测结果。

In arid and semi-arid loess regions,the water retention and permeability characteristics of compacted soil roadbed and loess overburden layer of landfill are all affected by temperature variation.To investigate the influence of temperature variations on the hydraulic properties of compacted loess in a full suction range,we measured the soil-water characteristic curve(SWCC)and hydraulic conductivity curve(HCC)of compacted loess in Yan'an city with different temperatures using the filter paper method and the self-developed soil column instantaneous profile method.The results show that in the high suction range of compacted loess SWCC,the volumetric water content of soil decreases as temperature increases.While in the low suction range,the temperature effect on water retention capacity of soil is not obvious.The HCC of loess in the low suction range is significantly affected by temperature.The higher the temperature,the stronger the permeability.As the suction increases or the volumetric water content decreases to a specific value,the influence of temperature on soil permeability can be ignored.Based on the results,the modified van Genuchten(VG)model is used as the prediction function of SWCC with the temperature effect taken into account.The parameters related to temperature are obtained by fitting the measured data.For the HCC,the 90 kPa matric suction is taken as the subsection point.The statistical model and power function are respectively used for the subsection prediction in the low suction range and high suction range.The prediction results are in good agreement with the measured data.