Ultimate Pullout Capacity of Granular Pile Anchors inHomogenous Ground

摘要

Granular piles (GP) well known for their ability to transfer compressive loads to the ground cannot resist tensile or pullout loads because of the inherent nature of granular materials. However, granular pile can be made to resist pullout forces by a simple modification of providing a pedestal/geogrid/metallic plate at the bottom and attaching a cable or a rod to the same to transmit the pullout or uplift load. Granular pile with a plate at the bottom that is connected to the footing through a cable or rod is termed as Granular Pile Anchor (GPA). The paper presents a method for the estimation of the ultimate pullout capacity of GPA in homogeneous (constant undrained strength) ground conditions as the lesser of the two values obtained considering pile and bulging failure mechanisms. The ultimate pullout capacity and the critical length of GPA corresponding to a transition from pile to bulging failure are evaluated as functions of various parameters such as the length to diameter ratio, L/d, of GPA, the ratio of the shear modulus to undrained strength, G/cu, of the ground, the undrained shear strength of soil, Cu, and unit weight, γ_(gp) and the angle of shearing resistance, 4g, of the granular pile material, lateral coefficient of earth pressure, K_0, etc. The predicted ultimate capacities compare well with those obtained from limited available experimental results.