Abstract: For the socketed piles under vertical load, pile-rock joint shear dilation effect has a great influence on side friction. This issue is based on a nonplanar failure model of pile-rock joint. Firstly, the value of shear force is solved when asperity fails by means of the slip-line field theory, and the corresponding shear displacement is obtained. A shear function is established based on the shear dilation mechanism, and the comparison with the experimental results shows a good correspondence. Secondly, based on the derived shear function, the load transfer equations for the pile are established considering the dilation effects, and the expression for load transfer of the pile is deduced. Furthermore, the effect of several parameters on plastic shear force is analyzed, such as joint roughness and rock strength and normal stiffness. Finally, a project is taken as an example, and the load transfer curve of the pile is calculated and compared with the measured one. The results are in good agreement with the measured data, which verifies the availability of the proposed method.