Influence of helix geometry on the cylindrical shear resistance of screw piles installed in granular soils based on direct shear tests

Gustavo Padros

In the proceedings of: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Posters - Geotechnical

ABSTRACT: A procedure is presented to compute the Cylindrical Shear Resistance (CSR) of screw piles installed in granular soils subjected to compressive loads using the shear strength and displacements measured in Direct Shear Tests (DST), based on the inferred similarity of the deformation pattern of the soil located between the helices and the deformation pattern observed in soils subjected to DST tests. A geometric ratio is used to establish a correspondence between the screw pile configuration and the shear box size. A correction factor is applied to the shear strength determined in the DST tests to account for differences in the geometric ratio, such that it may be used for CSR computation. The results indicate that for a given helix spacing and a given compressive load, an increase in the helix diameter will produce an increase in the shear strength developed by the soil located between the helices, provided the helix spacing remains constant. However, this increase in soil shear strength requires a larger pile vertical displacement. Similarly, it is postulated that for a given compressive load, the soil shear strength will increase as the helix spacing is decreased, requiring a larger pile vertical displacement to achieve this greater soil shear strength.

RÉSUMÉ: Voici une procédure pour calculer La Résistance Cisaillement Cylindrique (RCC) des pieux helicoidaux soumis a des cissaillement direct (ECD). Ceci, ayant come base la similarite inferée a la forme des déplacements du sol en piux de helicoidaux et les dimensions de la boite cisaillement directe. On applique un facteur por corriger la resistance séparation entre les hélices et une force de compression données, une accroisement du diametre des hélices produira une augmentation de la résistence cisaillement du sol. Ceci, tenant compte que la séparation entre les hélices soit constante. Egalement, on postule que tenant une forcé de compréssion et un diametre des hélices donnés, la résistance cisaillement du sol augmentara en mesure que la séparation entre les hélices diminue. Afin de dévélopper cette majeur

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