Abstract: To reveal the longitudinal mechanical behavior of void concrete pipes and the resilience improvement of self-expanding polymer external grouting, three full-scale tests and 3D finite element numerical simulations of dense, void, and polymer-repaired concrete pipes were performed, and the numerical models were verified by the test results. Selecting the longitudinal bending moment of the pipe section and the vertical displacement of the crown under different bedding conditions as analysis objects, the impacts of void length and void width on the mechanical behavior of concrete pipes were discussed, and the ξ_M and ξ_U referring to the longitudinal bending moment and vertical displacement repair indices were introduced to quantitatively characterize the resilience improvement effect of the repaired pipes. The results show that the positive and negative longitudinal bending moments of the void pipes are distributed in the adjacent pipe sections and joints on both sides of the void, and the peaks are located at SgL2, SgR2 and SgL3, SgR3, respectively. The longitudinal moments of void pipes decrease with the increasing void width at SgL1 and SgR1, increase with the increasing void width at remaining measuring points, and increase with the increasing void length in the whole longitudinal length. The longitudinal moments of pipes with different void widths and void lengths are higher than those of the dense pipes except for SgL1 and SgR1. Compared with the dense pipes, the maximum increases in vertical displacement and joint shear displacement of the void pipes are 155% and 230%, respectively; the longitudinal bending moments of the repaired pipes are slightly lower and the vertical displacements are slightly higher than those of the dense pipes, and the maximum repair indices of longitudinal bending moments and vertical displacements are 76.5% and 83.7%.