Physical modelling of helical screw piles in sand
Résumé
Empirical correlations between installation torque and uplift capacity of helical screw piles are frequently employed as a procedure for on site quality control of this type of foundation. In this work a theoretical relationship between uplift capacity and installation torque of deep helical screw piles in sand is proposed. The component of this relationship related to the contribution of helical plates to the uplift capacity was verified by centrifuge modelling in the Laboratoire Central des Ponts et Chaussées (Nantes). Twelve model piles with different number of helices and diameters were tested in reconstituted sand samples with different relative densities. The pile installation and pull-out tests were carried-out in flight. Direct shear interface tests were conducted to characterize the interface between soil and pile. The experimental results were compared with the values predicted by the suggested theoretical approach. This comparison showed good agreement between the measured and calculated uplift capacity.