Axial load capacity for an instrumented pile model: A review of Alpha and Beta methods

Miguel Rufiar, Manuel J. Mendoza, Enrique Ibarra

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Laboratory Testing

ABSTRACT: The instrumented model of a tubular friction pile, 2.64 cm in diameter and 90 cm long, was tested under axial loading. Some compression testing results are shown and discussed in this paper. The pile was driven making use of a hammer in a soft marine clay, recovered from the Sonda de Campeche sea bed, that was reconstituted in an oedometer with almost 1 m diameter. For two vertical pressures applied on the surface of the soil mass, compression pile tests were conducted under different displacement velocities. Different theoretical solutions for load capacity of friction piles, given by a and b-Methods, are compared with experimental results. The convenient approach established by the American Petroleum Institute (API) has been verified, that even for a total stress analysis, the a-value is a function of the effective stress, through the resistance ratio y = cu/sv.

RESUMEN: En este artículo se presentan algunos resultados de los ensayes de carga estática de compresión monotónicamente creciente, practicados en el modelo tubular instrumentado de un pilote de fricción de 2.64 cm de diámetro y 90 cm de longitud. Los ensayes fueron realizados después de hincar a golpes los modelos en la masa del suelo reconstituido en un odómetro de casi un metro de diámetro. Las pruebas se efectuaron variando la velocidad de deformación, y bajo dos presiones verticales diferentes aplicadas en la superficie del suelo. Se llevaron a cabo determinaciones de resistencia al esfuerzo cortante del suelo reconstituido, y se revisaron diversas soluciones teóricas que proporcionan los métodos a y b para predecir la capacidad de carga por fricción. Se confirma la pertinencia del enfoque del American Petroleum Institute (API) en el que incluso en una solución en términos de esfuerzos totales, para definir el factor a se hace intervenir el esfuerzo vertical efectivo, sv, a través del cociente de resistencia y =cu/sv.

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