Study of formation of stress arches in open-ended pipe pile

Plugging of pile happens mainly due to the internal side wall friction, which in turn depends on the vertical stress, which increases sharply at the bottom end of the pile at the time of plugging. This supports the idea of formation of stress arches at the bottom end of the pile. Extensive FEM analysis of axially loaded pipe-piles has been performed to simulate the formation of stress arches. Very clear stress arches are seen at the bottom end of the open-ended pipe pile. The depth of formation of those stress arches increases with the increase in pile length to diameter ratio. A comprehensive laboratory tests scheme is undertaken to find out the minimum length to diameter ratio of the open-ended pipe-pile for the start of plugging as well as the increase in its bearing capacity. Five different length to diameter ratio of pipe pile are used to validate the findings from numerical simulation using the same sand. Formation of stress arches is also verified experimentally by measuring stresses on the inner surface of the pile.