Influence of estimation method of compression index on spatial distribution of consolidation settlement in Songdo New City

Abstract

This paper describes the influence of the method that estimates the compression index (Cc) on the spatial distribution of consolidation settlement (sc) for Songdo New City. The spatial distribution of consolidation settlement can be evaluated by using the spatial distribution (Case 1), mean value (Case 2), and probability distribution (Case 3) of soil properties. For Case 1, ordinary cokriging was adopted to estimate the spatial distribution of Cc as it provides more reliable estimates than ordinary kriging. It is observed that the spatial distribution of sc for Case 1 has significantly shorter scale variability than that for Case 2 because the short scale variability of the spatial distribution of Cc and void ratio (eo) affect the spatial distribution of sc for Case 1. It is also shown that the ratio of the area of sc>100cm (design criterion) to the total area for Case 1 (7.7 %) is larger than that for Case 2 (0.5 %) because the ordinary cokriging estimate of Cc is larger than the mean value of Cc in some regions. The probabilistic analysis (Case 3) shows that the ratio of the area of P(sc>100cm)>probabilistic criterion (α) to the total area increases as the coefficient of variation (COV) of Cc/(1+e0) increases and α decreases. For Songdo New City, the area ratio for the probabilistic design criterion (α) of 0.30–0.45 is found to be in the range of 2.9–19.4 %.