Compaction control and related stress–strain behaviour of off-shore land reclamations with calcareous sands

AbstractWhen constructing off-shore land reclamations, one aims to ensure that the final soil mass fulfills certain minimal criteria related to shear strength, stiffness and resistance against liquefaction. In general, these characteristics improve with increasing density of the soil mass, which means that the above criteria are usually condensed into a single one: ‘adequate densification’.Quality control of reclamation constructions therefore focuses on the latter. Technical requirements are written based on one single parameter: the relative density Dr. On the site, this parameter is commonly determined indirectly using correlations with the cone penetration resistance qc, making the CPT the main tool for quality control.The paper presents data gathered during the design and construction of an off-shore land reclamation using calcareous sands. For this specific project, density control had to be done through the use of CPT.Calibration chamber tests were performed to establish the CPT qc–Dr correlation for the specific soil material. This correlation was used to analyse CPT results during construction of the site in order to determine the quality of compaction.In a further stage, an elaborate laboratory study was performed to establish additional correlations between soil parameters and the stress–strain parameters. Furthermore, seismic CPT tests were executed on the site to test the relevance of the laboratory correlations and the ‘relative density approach’ in general.It is shown that off-shore land reclamations have a very erratic stress-history, due to the different processes of depositing the soil material and the various densification methods. This stress-history is of great importance in the stress–strain behaviour of the site. Results also suggest that the CPT does not provide enough data to reliably predict soil stiffness when dealing with crushable materials. Specifically, in situ measurements show that there is no direct correlation between the small strain shear modulus G0 and qc

Barrières d'étanchéité dans les sites de décharges : développements récents

Depuis le début des années 80 la mise en décharge des déchets est devenue un domaine particulièrement sensible. Ceci a conduit à la promulgation de nouvelles réglementations au sein de la Communauté européenne et internationale. La conséquence immédiate a été l'apparition d'une multitude de règlements régissant la construction des barrières d'étanchéités des sites de décharges. Ce texte passe en revue les récents développements dans ce domaine avec une attention toute particulière aux problèmes liés au transport des contaminants, sols non saturés et le contrôle de qualité de la barrière argileuse. Finalement un cas d'étude concernant l'utilisation d'un matelas bentonitique est présenté

Most wiszący przez Cieśninę Messyńską Geotechniczne rozwiązania inżynierskie

Inżynieria Morska I Geotechnik