Abstract: The evaluation of compression index of soil is of great significance to the settlement of foundation soils which will have an impact on the size and dimensions of foundations. This paper analyses the correlations among three physical parameters of soil, namely void ratio, moisture content, and liquid limit. An empirical formula is then developed. The results show that there is a good linear relationship among the void ratio, moisture content, liquid limit, and compression index. Coefficient of Determination (R²) values are 0.837, 0.823 3, 0.691 0, respectively. At the same time, special attention is paid to the cone penetration test with pore water measurement (piezocone) method for the soft soil in-situ testing. Based on the piezocone data obtained from an economical housing project in Nanjing city, and combined with soil laboratory test data, the compression index of soil is analyzed and the accuracy of predicting it through the piezocone testing is evaluated. The results show that the cone tip resistance is correlated with the compression index, and the correlation coefficients of different soil layers vary (clay > silty clay > sandy soil). When the correlation coefficient takes a specific value, the compression index of each soil layer could be predicted accurately by a formula and the compressibility of each soil layer can be evaluated.

Key words: Piezocone Penetration Test, Compression Index, Vois Ratio, Moisture Content, Liquid Limit