This paper presents a new numerical solution for undrained lateral capacity of I-shaped concrete piles in accordance with the Thailand Industrial Standards. Two-dimensional finite element limit analysis with a plane strain condition in the direction of pile depth was employed to determine the stability of this problem. Six sections of I-piles were analyzed while parametric studies of each section were performed for a complete range of adhesion factors at the soil-pile interface, from smooth to rough piles, and two loading directions, where the I-pile was loaded normal to its major and minor axes. Failure mechanisms of the I-pile and its lateral capacity are discussed between different loading directions and compared with those of square piles. Design charts of all I-pile sections following Thailand Industrial Standards are proposed for an accurate and convenient prediction of undrained lateral capacity of I-shaped concrete piles in practice.
