Influence of the Carbonate Content on CPT-Results and Practical Relevance for the Soil Improvement Works on Major Land Reclamation Projects

This paper describes the challenges that arise during quality control of deep vibro-compaction works on land reclamation projects realized in the Middle East. The aim of deep vibro-compaction is to densify the fill to a certain relative density D_r and thereby assure certain minimal criteria related to the soil behavior such as stiffness and resistance against liquefaction. For quality control of the compaction works, the achieved relative density throughout the hydraulic fill can be measured indirectly by performing Cone Penetration Tests (CPT). The targeted relative density is linked to a cone resistance curve calculated with well-known and established correlation methods like Schmertmann [1] or Baldi [2]. However, the use of these empirical correlations in calcareous sand is questionable because they are not suitable to reproduce the characteristics of these sands. Almeida et al. [3] have shown that carbonate sands show significantly lower q_c-values than silica sands under similar conditions which can lead to unattainable target cone resistance values demanded by the client.

In this paper, the Karlsruhe Interpretation Method (KIM) is used as an alternative approach to traditional CPT interpretation methods in sands that contain a high carbonate content. The KIM has shown to be able to accommodate the intrinsic characteristics of calcareous sands and more reliable in establishing a correlation between the cone resistance q_c and the relative density D_r.