黄土填方场地工后持水特性及雨水入渗研究

Water Retention Behavior and Rainfall Infiltration of Loess Filling Site

通过压力板仪测定了填方场地不同深度(1.0m、3.0m、5.0m)回填压实黄土的吸-脱湿持水特征曲线,并结合X射线衍射试验、压汞试验和现场含水量监测分析不同取样深度下回填压实黄土持水特性差异原因。结果表明:(1)不同深度回填压实黄土具有相似的粒径分布、矿物组成、孔径分布和干密度。(2)5.0m黄土持水特征曲线的平均滞回度(0.23)比1.0m和3.0m黄土(0.04和0.05)分别大475%和360%。1.0m和3.0m回填压实黄土持水特征曲线较小滞回效应可归结于现场经历了多次干湿循环而引起的时效作用。(3)分析不同深度黄土持水特性差异对土柱雨水入渗计算结果的影响发现,采用单一1.0m、3.0m和5.0m黄土水力学参数计算雨水入渗深度分别为4.0m、2.4m和1.2m,而采用考虑深度影响的黄土水力学参数计算雨水入渗深度为4.4m,这与现场含水率监测结果较为一致。建议在进行黄土高填方工后渗流分析时,考虑不同深度黄土由于经历干湿循环历史不同造成的水力学参数差异。

The water retention curves of backfill compacted loess at different depths(1.0 m,3.0 m,5.0 m)were measured by pressure plate instrument,and the reasons for the difference of water retention characteristics of backfill compacted loess at different sampling depths were analyzed by using X-ray diffraction test,mercury injection test and on-site water content monitoring.Results show that loess from different depths have similar particle size distribution,mineral composition and pore size distribution,but the average degree of hysteresis at 5.0 m depth(i.e.,0.23)is475%and 360%larger than that of the loess at 1.0 m(i.e.,0.04)and 3.0 m(i.e.,0.05)depths,respectively.The smaller hysteresis of loess at 1.0 m and 3.0 m depths is probably attributed to wetting-drying cycles in situ.The rainfall infiltration of loess column is analyzed and results show that the infiltration depth calculated by hydraulic parameters of loess at 1.0 m,3.0 m and 5.0 m are 4.0 m,2.4 m and 1.2 m respectively.The result calculated by hydraulic parameters considering depth effects is 4.4 m,which is consistent with field monitoring results.It is suggested that depth effects on hydraulic parameters should be considered for the seepage analysis of backfill loess.