Sand state from cone penetrometer tests: a framework considering grain crushing stress

• Published in: Géotechnique
• Main Author: Konrad, J.-M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Thomas Telford Ltd. 1998
• Subjects: Beaufort Sea
• Online Access: http://dx.doi.org/10.1680/geot.1998.48.2.201; https://www.icevirtuallibrary.com/doi/pdf/10.1680/geot.1998.48.2.201

Thekey factors that control the value of cone penetrometer tip resistance in cohesionless soils were assessed in order to develop a rational framework for interpreting the results of cone penetrometer tests (CPTs) that would allow confident determination of thein situ sand state. Using the University of Laval calibration chamber, measurements were made of the response of an instrumented cone tip in Ticino sand, Kenamu sand and Québec sand placed at various densities and subjected to different initial stress levels. Triaxial compression tests were also performed on the same sands to define the relevant parameters at the critical state. It was established that it is important to consider the characteristics of a sand at which shear-induced grain crushing occurs, hence the bi-linear nature of the critical state line. The complete characterization of a sand by interpretation of CPTs is given by the void ratio, the mean effective stress at grain crushing and the slopes of the critical line (λ for stresses smaller than the stress corresponding to shear-induced grain crushing; λ, for larger stresses, at which grain crushing is predominant). The results of a CPT are best interpreted in terms of the normalized tip resistance, the normalized state parameter, the initial mean effective stress and the stress at the critical state. Using Ticino sand as a reference, it was possible to obtain a unique normalized CPT response for all the sands studied, including a sand from the Beaufort Sea. The usefulness of the proposed approach under field conditions is explored. L'article examine les principaux facteurs qui influent sur la résistance de sols sans cohésion à la pointe ďun cÔine de pénétration, en vue ďďtablir un cadre rationnel ďinterprétation des résultats ďessais de pénétration au cône qui puisse offrir une détermination fiable de ľétat des sables en place. Ľauteur a effectué des essais en laboratoire dans la chambre ďétalonnage UL pour examiner la réaction ďune pointe de cône instrumentée dans du sable du Tessin, du sable ...