Soil arching effect is an important basis for theoretical research of pile-soil interaction. But due to less research on the soil arching effect mechanism of anti-slide piles with different cross-sec- tions， the traditional cross-section is mostly used in the design of anti-slide piles. Considering the shortcomings of traditional rectangular anti-slide piles in forming soil arching effect， the trapezoidal cross-section was proposed to optimize the design of the anti-slide piles. Based on the theory of materi- al mechanics， the stress state in the compression zone at the foot of the soil arch on the side of the trap- ezoidal piles was deduced by using the oblique section stress calculation model of the axial compres- sion bar， and the ultimate bearing capacity of the trapezoidal piles was obtained by combining the Mohr-Coulomb strength criterion. The ultimate bearing capacity of the soil arch on the side of the trap- ezoidal and rectangular piles was analyzed by a numerical example， and the theory and calculation re- sults were verified by a numerical simulation analysis. The results show that the ultimate bearing ca-pacity of the trapezoidal piles is significantly improved compared with that of the rectangular piles， and the maximum bearing capacity is about 2.5 times that of the rectangular piles； Under the same condi- tions， the increment of soil displacement and shear strain between trapezoidal piles is smaller， while the stress concentration is more obvious. The trapezoidal sectional pile is more favorable to the forma- tion and development of soil arching effect.
