中文摘要：

黄土作为地基材料时由于其湿陷性容易出现失稳现象,利用固化剂垫层改良黄土地基水稳性和强度的技术被广泛使用.本文主要通过在黄土中分别加入石灰、水泥和粉煤灰固化剂垫层的方法进行加固,测定了在垂直方向上各处的含水率、密度、干密度、土颗粒比表面积（SSA）及阳离子交换能力（CEC）的变化.试验表明石灰、水泥和粉煤灰垫层可以影响10～15cm范围内相邻土层含水率、密度、比表面积和阳离子交换能力,改变土质结构,提高土体的水稳性.改性后的土体越靠近固化剂垫层,含水率、SSA和CEC越小而密度越大.其中,石灰垫层效果最好,它能将黄土中含水率减小超过4%,密度增加1.0～1.5g·c^m-3,粉煤灰作用次之,水泥最弱.此外,试样土颗粒比表面积（SSA）与阳离子交换能力（CEC）存在线性递增的关系,本次试验中,3个试样中SSA与CEC之比均稳定于6.5～7.5之间.

英文摘要：

Loess has the collapsibility characteristic.Loess can have the phenomenon of unstability when it is used as foundation materials.The technique of using strengthening materials cushion to improve water stability and strength of loess foundations has been widely applied.In this test,cushions made of lime,fly ash and cement are added into loess separately.The moisture content,density,dry density,Specific Surface Area(SSA)and Cation Exchange Capacity(CEC)of the loess at different places in vertical direction are measured.Results indicate that the lime,fly ash and cement cushion all have considerable impact on the moisture content,density,SSA and CEC of adjacent loess(1 0~1 5cm),changing the microstructure and enhance the water stability of the loess.The closer to the cushion,the smaller the moisture content,SSA and CEC are and the greater the density is Lime cushion has the best effect.It can reduce over 4%of the moisture content,increase 1.0~1.5 g·cm-3 of the loess density.Effects of fly ash are weaker and cement the weakest.Additionally,the SSA and CEC have a linear increment relationship.In the present test,the rate between SSA and CEC of the three tests is controlled between 6.5~7.5.