According to the time-settlement data of an expressway in Taihu Lake region and the laboratory test results

the compression characteristic of alluvial lacustrine soft soil and the variation of settlement for subgrade are analyzed. The effect of engineering geological conditions and depth of fill on settlement of subgrade are investigated. The normalized index is used to estimate the settlement of subgrade. Meanwhile

two kinds of commonly used whole process subgrade settlement prediction methods are compared. The results show that the alluvial lacustrine soft soil in Taihu Lake region is a strong structured soil. The settlement of subgrade at similar geological conditions is quite different and soil structure is one of the important factors affecting the settlement of subgrade. A simple formula for estimating settlement is obtained with the analysis of normalized index. The whole process settlement prediction methods commonly used for the final settlement prediction have certain deviation; a more accurate estimated value of settlement can be got by comprehensive analysis.