Abstract: An improved method for calculating the anti-overturning safety factor of supporting structure with double-row piles is presented. The method takes into consideration the influence of compressive resistance of first-row pile and uplift resistance of back-row pile coupled with groundwater buoyance. The calculation methods for anti-overtur-ning safety factor of double-row piles and gravity retaining structure in different specifications in China are compared. The compositions of overturning force and overturning resistance are also analyzed. The calculation results of engineering cases show that compared with the results calculated by specification formulas, the anti-overturning safety factor calculated by the present method could improve by 20%-55%. The influence factors of anti-overturning safety factor are analyzed by a self-developed software, and the results indicate that with the increase of built-in depth of supporting pile, the anti-overturning safety factor of double-row pile decreased firstly but then increased. The impacts of the torque generated by the coupling between compressive resistance of first-row pile and uplift resistance of back-row pile on the safety factor weakened. Moreover, with the increase of array pitch, the anti-overturning safety factor increased approximately linearly, and impacts of the torque generated by the coupling between compressive resistance of first-row pile and uplift resistance of back-row pile on the safety factor strengthened.

Key words: deep foundation pit, double-row piles, stability against overturning, built-in depth, array pitch