低温条件下水泥搅拌饱和黄土的强度特性研究

Research on Strength Characteristics of Cement Mixing Saturated Loess at Low Temperature

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.由于该地区冬季气温较低,需要探究温度对水泥搅拌饱和黄土强度的影响,以便确定在冬季温度较低的情况下能否施工以及低温环境下水泥搅拌饱和黄土的强度增长规律.通过室内试验研究低温条件下水泥搅拌饱和黄土无侧限抗压强度随水泥和粉煤灰(以下简称"二灰")掺入比、养护龄期、养护方式的变化规律.试验表明:低温条件下水泥搅拌饱和黄土的无侧限抗压强度也随二灰掺入比增加、养护龄期的增长而增大;低温水中养护条件下水泥搅拌饱和黄土的无侧限抗压强度较标准水中养护(20±1℃)的强度低,龄期为28d、掺入比为12%的抗压强度为标准水中养护条件下的36%,掺入比20%的抗压强度为标准水中养护条件下的33%;随着养护龄期的增大,低温水中养护条件下抗压强度与标准水中养护条件下的差距逐渐增大,龄期为60d、掺入比为12%的抗压强度是标准水中养护条件下的26%.

Most sections of railway from Lanzhou to Zhongchuan Airport are saturated loess foun-dation,taking cement soil mixing pile composite foundation to strengthen the sections.Because of the low temperature in winter of this area,it is necessary to study the effects of temperature on the strength of cement mixing saturated loess,so as to make sure whether the construction is fea-sible or not and to study the growth rule of cement mixing saturated loess＆#39;s strength at low tem-perature.The change rule of unconfined compressive strength of cement mixing saturated loess with the change of the mixing ratio of cement,fly ash,curing period and curing ways at low tem-perature is researched by laboratory tests.The research shows that the compressive strength of cement mixing saturated loess increases with the increase of two ash mixing ratio and the exten-sion of curing period at low temperature,and the compressive strength of cement mixing saturated loess conserved in low-temperature water is lower than in standard temperature water（20℃＆#177; 1℃）.When the curing period is 28 d,and the mixing ratio is 12% and 20% respectively,the com-pressive strength in low-temperature water is 36% and 33% respectively of that in standard-tem-perature water.With the extension of curing period,the gap between compressive strength of ce-ment mixing saturated loess conserved in low-temperature and in standard water is gradually en-larged.When the curing period is 60 d and the mixing ratio is 12%,the compressive strength in low-temperature water is 20% of that in standard temperature water.