Abstract:
Under embankment load, subgrade tends to produce large lateral deformation, and it is necessary to adopt reasonable lateral restraint structures. Positive-negative inclined double-row piles have been studied in foundation pit engineering, but are rarely reported in subgrade engineering, and their engineering characteristics remain unclear. Taking the test section of the Huizhou-Zhaoqing Expressway in Guangdong Province as the research object, a 1∶1 numerical model was built with Plaxis
3D software. The positive-negative inclined double-row pile was simplified as a planar rigid frame under lateral uniform load. The influences of the stiffness ratio between the rear positive inclined piles and front negative inclined piles on the horizontal displacement and bending moment of piles under embankment load were analyzed, and the variation of peak bending moment ratio with stiffness ratio was verified by the displacement method. The results show that: (1) When the stiffness of positive and negative inclined piles is equal, the horizontal displacement of piles first increases and then decreases downward from the pile top. The peak displacement of the rear positive inclined pile is 1.2 times that of the front negative inclined pile. The bending moment of positive and negative inclined piles presents an inverted “S” shape with depth. The bending moment of the rear positive inclined pile is significantly larger than that of the front negative inclined pile, and the peak positive bending moment occurs at 1/4 of the pile length. (2) Keeping the stiffness of the front negative inclined pile constant, increasing the stiffness ratio reduces the peak displacement and peak bending moment of the front pile, decreases the peak displacement of the rear pile, and increases its peak bending moment, leading to a larger peak bending moment ratio. Keeping the stiffness of the rear pile constant, increasing the stiffness ratio increases the peak displacement of the front pile and reduces its peak bending moment, while both the peak displacement and peak bending moment of the rear pile increase. (3) When the stiffness ratio of the rear positive inclined pile to the front negative inclined pile is about 9, the ratio of peak bending moment ratio to stiffness ratio is close to 1, indicating the optimal bending moment distribution. Increasing the stiffness of the front negative inclined pile is unfavorable in engineering. It is suggested that the stiffness of the rear positive inclined pile be increased to about 9 times that of the front pile to resist greater bending moment. The research results can provide a basis for the design of positive-negative inclined double-row piles at the slope toe.