黄土-碎石覆盖层毛细阻滞效应及设计厚度分析

Analysis of capillary barrier effect and design thickness with loess-gravel cover

为了研究我国西北地区以黄土和碎石构成的毛细阻滞覆盖层适用性,验证黄土-碎石间的毛细阻滞效应以及覆盖层初步设计厚度,在西安江村沟垃圾填埋场开展黄土-碎石毛细阻滞覆盖层极端降雨实验.实测黄土-碎石毛细阻滞覆盖层的储水能力,验证了黄土-碎石间的毛细阻滞作用,分析西安地区半湿润气候条件下毛细阻滞覆盖层的初步设计厚度.研究结果表明：在黄土层同为1.0m厚的条件下,毛细阻滞型覆盖层与单一型覆盖层相比,总储水量提高了24.9%？31.8%,有效储水量提高了38.2%-48.9%.现场实测黄土-碎石毛细阻滞覆盖层储水量为116.92mm,而按脱湿和吸湿曲线计算理论储水量分别为137.68和88.30mm.与本次降雨实测的存储量相比,分别偏大17.76%和偏小24.42%.对于黏性黄土分别下衬碎石、粗砂和中砂构建的毛细阻滞覆盖层：若采用黄土脱湿曲线计算初步设计厚度为1.06-1.12m,而采用吸湿曲线初步设计厚度为1.22-1.28m.在黄土毛细阻滞覆盖层厚度设计中,若采用脱湿曲线计算偏于危险,而采用吸湿曲线则偏于安全.

The capillary barrier effect of clayey loess-gravel cover was verified and preliminary design thick-ness was analyzed in order to study the applicability of capillary barrier cover with loess and gravel in the northwest of China. Extreme rainfall test was conducted on the loess-gravel capillary barrier cover at Xi’ an,Jiang Chun landfill. Water storage capacity of the cover was measured. The capillary barrier effect in clayey loess-gravel cover was illustrated and the thickness of loess capillary barrier cover was analyzed. Compared with the monolithic cover with 1 m thick loess layer, the total water and effective water storage capacity for the capillary barrier cover with the same thickness of loss layer were increased by 24. 9 % - 31. 8% and 38. 2%-48. 9% , respectively. The maximum water storage in the loess-gravel capillary barrier cover was measured as 116. 92 mm in the extreme rainfall test. Compared with the field measurement, the theoretical value of water storage calculated by drying SWCC was 10. 91 % greater, and theoretical value of water storage calculated by wetting SWCC was 16. 40 % lower. When using the gravel, coarse sand and medium sand as a coarse soil and using the clayey loess as a fine soil to form a capillary barrier cover, the preliminary design thickness of the loess cover was between 1.06-1. 12 meters calculated by drying SWCC, and it was 1. 22？1. 28 meters by wetting SWCC. In the preliminary design of cover, the thickness calculated by drying SWCC was conservative and it was non-conservative by wetting SWCC.