Abstract: As a new bracing structure, the portal double row piles have some advantages such as larger rigidity, less displacement in the top of the piles and large anti-force, which leads to the restriction of piles deformation. The key problem is concentrated on the determination of the action of soil between the double piles. On the basis of combining the front and the back row piles as well as connecting beams and soils as a whole structure, and simplifying the forces for the double row piles from the soils as elastic bearing, a new analytical mode and a new calculation model are proposed. From the viewpoint of the authors, the front row piles sustain not only the active earth pressure but also the additional one due to the press of the soils between the double piles. The ratio of the active earth pressure for the double row piles to the active earth pressure for the single ones is a parabola function of the ratio of interval of the piles to the diameter of the piles. The action of the soils to the back row piles is considered as elastic bearing; its mathematical and mechanical model for the internal force of portal double-row piles is established by finite element method and Winkler beam on elastic foundation method. The application of the models to the water supply reconstruction project from Dongjiang to Shenzhen shows that the new mode and the calculation model is reasonable and can be used in the similar engineering.

Key words: portal double row piles, interaction model of piles and soils, finite element analysis, reinforcement of a slope, new mode