Abstract: Y-shaped vibro-pile is a new type of pile, compared with the traditional circular pile, the Y-shaped cross-section pile increases the contact area of the pile and soil, and thus increase skin friction and the bearing capacity. Due to the particularity of the pile cross-section, when Y-shaped pile is driven by pipe with vibration, different area of Y-shaped section have varying degrees of compression on the soil and its skin friction distribution trait is complicated than circular pile. Simplifying Y-shaped pile skin friction as rectangularly distributed along the pile length direction and uniformly distributed along the section perimeter direction does not match with the actual and the engineering experience also shows its inappropriate. Firstly, combining the cavity expansion theory and the analytical equations of Y-shaped section to deduce the nonuniform distribution, it is shown that the maximum skin friction is 1.24-1.75 times larger than the minimum skin friction at the same cross-section; the influences of three variables R, θ, L of Y-shaped pile on skin friction are also analysed. The total skin friction can be calculated by quadraturing the skin friction along nine integral regions of the Y-shaped section and the pile length direction，combined with the tip resistance，the ultimate bearing capability is obtained and consistent with the data of static loading test.

Key words: Y-shaped vibro-pile, skin friction, cavity expansion theory, nonuniform distribution model