Evaluation of failure mechanism of pile under pullout test in loose sand by PIV method

Abstract

In order to ensure safe design of structures we need to study on behavior of structure’s components before and after failing. Consequences effects of failing are important in some structural cases. For instance, piles as a member of structures can be failed because of structural collapses or soil’s body failure. Extensive experimental investigations have been carried out to study the behavior of failure mechanism of piles in sand subjected to axial compressive, inclined, or lateral loads. However, studies regarding piles subjected to uplift load are limited. This study reports a series of small scale physical modeling test designed to investigate the uplift resistance of piles with diameter of 5cm and with slenderness ratio L/D=1,2,3 and 4 in loose sand with unit weight of 14.2 kN/m2. A close photogrammetric technique and Particle Image Velocimetry (PIV) were employed to observe the failure patterns due to uplift force on pre formed concrete piles with a different slenderness ratio. The results from the laboratory tests were verified with a Finite Element Method software (PLAXIS 2D and 3D) and analytical method proposed by B. C. Chattopadhyay1et.al (1986). It was found that, the depth of the failure surface increases with the increase of the slenderness ratio. An acceptable agreement has been observed between the measured and predicted values of uplift capacities (PLAXIS 2D and 3D)