Advertisement

Origine de la sensibilité des sédiments marins de grande-baleine, Québec, Canada

  • Jacques Locat
Article

Résumé

Les sédiments de la rivière Grande-Baleine furent déposés dans une eau saumâtre, il y a environ 7 000 ans; la salinité n'était pas moins de 8 g/l. Ces dépôts argileux ont été soulevés plus de 150 m au-dessus du niveau de la mer. Le sol est extrêmement sensible (St plus grand que 200 tel que mesuré au cône suédois). L'indice de liquidité est souvent au-dessus de 2. A l'oedomètre, ce sédiment est très compressible et présente un rapport de surconsolidation de plus de 2 et ce, avec peu de signes d'érosion. Les travaux de recherche ont donné un modèle qui comprend différents processus tels que: une cimentation précoce durant ou tôt après la déposition et le lessivage jusqu'à l'actuelle salinité interstitielle de 0.5 g/l. Les deux procédés ont résulté en un sédiment à une teneur en eau anormalement élevée (par rapport aux contraintes effectives) et un indice de liquidité élevé dû en partie au lessivage. Des travaux sur le terrain et en laboratoire ont démontré que les processus responsables de la structuration de ce sol sont le lessivage et la cimentation (ou quoi que ce soit qui ait empêché ce sol de se consolider complètement). Aucune évidence n'a pu étre trouvée qui suggèrerait l'action du processus de consolidation retardée. Aujourd'hui, ce sol est géologiquement normalement consolidé (i.e. aucune érosion ou surcharge), et physico-chimiquement sous-consolidé (i.e. une teneur en eau plus élevée que celle normalement retrouvèe pour une même pression sur un sol resédimenté).

On the origin of structuration of the grande-baleine marine sediments, Quebec, Canada

Abstract

Sediments of the Grande-Baleine River were deposited in a brackish sea about 7000 years ago; the salinity was not less than 8 g/l. This fine-grained sediment was uplifted more than 150 metres above sea level. The soil is extremely sensitive (St greater than 200 as measured by the fall cone), the liquidity index is often above 2. In the oedometer, this sediment is highly compressible and presents an overconsolidation ratio greater than 2 and this with signs of little erosion. Research work has yielded a behavioral model that includes different processes such as early cementation during or soon after deposition and leaching to the actual porewater salinity of 0.5 g/l. Both processes have resulted in a sediment with abnormaly high water content (with respect to effective stress) and a high liquidity index in part due to leaching. Field and laboratory work demonstrate that for this soil, processes responsible for its structuration are leaching and cementation (or anything that has prevented the soil from consolidating completely). No evidence could be found that would suggest the action of delayed consolidation. Today this soil appears geologically normally consolidated (i.e. no erosion or surcharge), mechanically overconsolidated (O.R.C. more than 2), and physico-chemically underconsolidated (abnormally high water content).

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Références

  1. ANOUSHIRAVAN R. (1973): A theoretical and experimental study of one-dimensional consolidation of clays. Ph. D. thesis, University of Illinois, 217 p.Google Scholar
  2. BJERRUM L. (1967): Engineering geology of Norwegian normally consolidated marine clays as related to settlement of buildings.Géotechnique, 17, 81–118.Google Scholar
  3. — (1973): Problems of soil mechanics and construction on soft clays. State-of-the-art report to session IV, Comptes Rendus de la 8th International Conference on Soil Mechanics and Foundation Engineering, Moscou, vol. 3, p. 11–159.Google Scholar
  4. BJERRUM L. and ROSENQVIST I. Th. (1956): Some experiments with artificially sedimented clays.Géotechnique, 6, 124–136.CrossRefGoogle Scholar
  5. BUMRUNGSUP T. and MOH Z. (1972). Research on artificially sedimented clays. Asian Institute of Technology, Research Report, no. 28, 123 p.Google Scholar
  6. CASAGRANDE A. and FADUM R.E. (1944): Application of soil mechanics in designing building foundation.Transaction of the American Society of Civil Engineers, 109, 463–490.Google Scholar
  7. DENISSOV N.Y. (1965): Pore pressure and strength of underconsolidated clay soils. 6th International Conference on Soil Mechanics and Foundation Engineering, Paris, p. 208–212.Google Scholar
  8. HOUSTON W.N. and MITCHELL J.K. (1969): Property interrelationships in sensitive clays. Journal of American Society of Civil Engineers, 95: 1037–1062.Google Scholar
  9. LEFEBVRE G. and POULIN C. (1979): A new method of sampling in sensitive clay.Revue Canadicane de géotechnique, 16, 226–233.CrossRefGoogle Scholar
  10. LEONARDS G.A. and ALTSCHAEFL A.G. (1964): Compressibility of clays.Journal of the American Society of Civil Engineers, 90, 133–156.Google Scholar
  11. LOCAT J. (1982): Contribution à l'étude de l'origine de la structuration des argiles sensibles de l'Est du Canada. Thèse Ph. D., Département de Génie Civil, Université de Sherbrooke, Québec, Canada, 512 p.Google Scholar
  12. LOCAT J., LEFEBVRE G. and BALLIVY G. (1984): Mineralogy, chemistry and physical properties interrelationship of some sensitive clays from Eastern Canada.Revue Canadienne de Géotechnique 21, 530–540.CrossRefGoogle Scholar
  13. LOCAT J. and LEFEBVRE G. (1984): The compressibility and sensitivity of an artificially sedimented soil: the Grande-Baleine marine clay, Québec.Marine geotechnology, 6, 1–28.CrossRefGoogle Scholar
  14. MESRI G., ROKSHAR A. and BOHOR B.F. (1975): Composition and compressibility of typical samples of Mexico City clay.Géotechnique, 25, 527–554.CrossRefGoogle Scholar
  15. MONTE J.L. and KRIZEK R.J. (1976): One-dimensional mathematical model for large-strain consolidation.Géotechnique, 26, 495–510.CrossRefGoogle Scholar
  16. MURAKAMI Y. (1979): Excess pore-water pressure and preconsolidation effect developed in normally consolidated clays of some age. Japenese Society of Soil Mechanics and Foundation Engineering,Journal of Soils and Foundation, 19, 17–29.CrossRefGoogle Scholar
  17. OLSEN R.E. (1962): The shear strength property of calcium illite.Géotechnique, 12, 23–43.CrossRefGoogle Scholar
  18. QUIGLEY R.M. (1980): Geology, mineralogy, and geochemistry of canadian soft soils: a geotechnical perspective.Revue Canadienne de Géotechnique, 17, 261–285.CrossRefGoogle Scholar
  19. RICHARDS A.F. (1976): Marine geotechnics of the Oslofjorden region.In: Laurits Bjerrum Memorial Volume, Oslo, Norwegian Geotechnical Institute, N. Janbu, F. Jorstad and B. Kjoernsli, editors, pp. 41–63.Google Scholar
  20. RICHER D. (1980): Etude de quelques types d'essais de consolidation œdométriques. Mémoire M. Sc. A., département de Génie Civil, Université de Sherbrooke, Québec, Canada.Google Scholar
  21. SKEMPTON A.W. (1970): The consolidation of clays by gravitational compaction.Journal of the Geological Society of London, 125, 373–412.CrossRefGoogle Scholar
  22. SKEMPTON A.W. and NORTHEY R.D. (1952): The sensitivity of clays.Géotechnique, 3, 30–53.CrossRefGoogle Scholar
  23. SNEDDON R. (1967): One-dimensional consolidation of floculated clays. Ph. D. thesis, University of Wisconsin, 147 p.Google Scholar
  24. TORRANCE J.K. (1974): A laboratory investigation of the effect of leaching on the compressibility and shear strength of Norwegian marine clays.Géotechnique, 24, 155–173.CrossRefGoogle Scholar
  25. VAN OLPHEN H. (1977): An introduction to clay colloid chemistry. 2nd edition, Wiley, N.-Y., 318 p.Google Scholar

Copyright information

© International Assocaition of Engineering Geology 1985

Authors and Affiliations

  • Jacques Locat
    • 1
  1. 1.Groupe de Recherche en Géologie de l'Ingénieur, Département de géologieUniversité LavalQuébecCanada

Personalised recommendations