DETERMINATION OF PRECOMPRESSION STRESS OF AN ANDISOL (DURIC HAPLUDAND) USING TWO GRAPHIC METHODS

Abstract

The graphical method of Casagrande (1936) has been widely used in southern Chile to determine the soil bearing capacity, but no evaluation has been conducted to determine whether this method is better than that proposed by Pacheco Silva (1970) which is characterized by its simplicity, objectivity and more appropriability for use in soils with a high deformation capacity such as Andisols. Therefore, both of these graphical methods to determine the bearing capacity were compared using soil samples collected in an Andisol under 4 different types of pasture and applying successive loads to the soil samples during the consolidation experiment. To compare both methods, different graphical scales and the objectivity defined by the determination of the bearing capacity by different users were considered. Additionally, the relationship between this soil property and the penetration resistance measured on the field was determined. The results from both methods were well related when they were compared using a 1:1 graphic scale. The Pacheco Silva method presented lower values than Casagrande method. The latter is more subjective due to the interpretation by the user compared with the Pacheco Silva method; however, mathematically it has a better interpretation of the infection point between the elastic and plastic deformation. Finally, the precompression stress defined by both methods increased with an increase in the penetration resistance of the soil measured in the field.