Franz Tschuchnigg

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 Dr 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 qc-values than silica sands under similar conditions which can lead to unattainable target cone resistance values demanded by the client.

Estimation of Relative Density in Calcareous Sands Using the Karlsruhe Interpretation Method

The paper describes the challenges that arise during execution and quality control of deep vibro-compaction works on land reclamation projects realized in the Middle East. For quality control, the achieved relative density throughout the hydraulic fill can be measured indirectly by performing Cone Penetration Tests (CPT). Commonly used empirical correlations between the cone resistance qc and the relative density Dr are not suitable to reproduce the characteristics of carbonate sands, because these sands show significantly lower qc-values than silica sands under similar conditions. An alternative to traditional correlation methods to derive the qc-requirement is the use of the semi-empirical Karlsruhe Interpretation Method (KIM) which is based on numerical analyses of spherical cavity expansion (SCE) problems and results of calibration chamber tests. This paper explains the general procedure when applying the KIM with a focus on the specific characteristics of carbonate sands.

Investigations on Existing Concrete Cantilever Walls Subjected to Reinforcement Corrosion

Recently fatal collapses of reinforced cantilever walls occurred in the Alpine Region. Investigations on the collapsed walls showed that these constructions suffered from corrosion damage along the horizontal construction joint between the foundation and the vertical concrete wall, which is also the most sensitive region with respect to stresses. The detection of corrosion is a difficult task, since the critical areas are not easy to access, because they are situated on the backfill side of the structure and detection of corroded reinforcement elements is still a very challenging task.