The saturated loess foundation with sand lens is mostly distributed along the railway project of Lanzhou to Zhongchuan Airport,so the cement mixed pile foundation is applied.The strength properties of cement mixing sand are studied by experiment in different lime-fly ash in-corporation ratios,curing time and stirring uniformity,and the variation of unconfined compres-sive strength of the cement mixing sand is analyzed.The results show that the unconfined com-pressive strength of cement mixing sand increases with the increase of lime-fly ash incorporation, whose increasing from 7% to 20% makes the unconfined compressive strength of cement mixing sand increase by 160.1%,and it increases with the growth of curing period;it grows rapidly dur-ing 7 d to 28 d,and still grows much after 28 d;the compressive strength of age 90 d has good cor-relation with that of 28 d,so the strength of 28 d can be predicted from that of 90 d,thus to short-en the test cycle;furthermore,the unconfined compressive strength of cement mixed soil increases obviously with the increase of stirring uniformity,and the unconfined compressive strength of uni-form specimen increases by 238%~263% than that of uneven specimen.%兰州至中川机场铁路工程沿线大多地段为饱和黄土地基，设计采取水泥土搅拌桩复合地基加固；该线部分地段饱和黄土地基中含有呈透镜状分布的砂土．对水泥搅拌砂土在不同的水泥和粉煤灰（以下简称“二灰”）掺合比、养护龄期、搅拌均匀程度下进行强度特性试验研究，分析了水泥搅拌砂土无侧限抗压强度的变化规律．试验表明：水泥搅拌砂土无侧限抗压强度随二灰掺量的增加而增加，二灰掺入量从7％增加到20％水泥搅拌砂土的无侧限抗压强度增长了160．1％；随养护龄期的增加而增大，7～28 d 增长较快，28 d 以后仍有较大程度的增长，龄期90 d 抗压强度与28 d 强度有较好的相关性，可以用28 d 强度预测90 d 强度，缩短试验周期；随着搅拌均匀程度的提高，水泥搅拌砂土的无侧限抗压强度显著增大，搅拌非常均匀的试件无侧限抗压强度比搅拌极不均匀的试件增长了238％～263％．
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