上海黏性土与水泥混合后强度增长特性试验研究

Characteristics of strength increase of cement treated Shanghai clayey soils

对于使用水泥与上海黏性土进行混合加固的土体,其强度增长特性与水泥含量、加固土的初期pH值、养护时间有关。以上海4类黏土为研究对象,对加固土的强度增长特性进行了试验研究;探讨了加固土的养护时间、水泥含量、初期pH等与加固土强度的关系。试验结果表明,当上海黏土中水泥含量或者加固土的初期pH值大于某一临界值时,水泥加固土的强度将迅速增加,对于上海黏土,该临界pH值为11.7,对应的水泥含量为17%～20%。但当水泥含量达到一定值后,它对土体的pH值的影响开始变小,而且水泥土的强度趋于稳定的时间变长。

For soft clayey soil in Shanghai, the relationship among the strength of stabilized soils, cement contents, initial pH value and curing time is investigated experimentally. The strength obtaining mechanism of cement mixed clayey soil of Shanghai with curing time, cement contents and initial pH value is presented at first. Then, the strength obtaining mechanism of some typical Japanese clay compared with Shanghai clay is discussed. Limited laboratory test studies show that the strength obtaining of Shanghai clay is abruptly increased with the cement content larger than 17%-20% or the pH value is larger than a critical value（pile） immediately after mixing. For Shanghai clayey soils, the critical value pHc is 11.7. If the cement content is higher, it will take a long time for the strength of cement mixed Shanghai clayey soils to reach a steady value. This phenomenon is much different from that of cement mixed Japanese clay, of which strength is gradually obtained with the cement content.