Assessment of Earth Retaining Performance for Long-Short Piles Composite Structures from Field Experiments and Numerical Analysis

Retaining pile structure is commonly utilized in excavation maintenance design. In recent years, the long-short combined retaining piles have received more and more attention. According to the actual deep excavation engineering, the working mechanism of the long-short, long-double-short, and long-triple-short combined retaining piles was tested in the field. Based on the field test parameters, the finite element model of the test area was established and the simulation results were verified, and the effects of short pile length and pile spacing on bending moment, horizontal displacement of piles, surface settlement, and excavation bottom heave were further investigated. The results show that the bending moment of the long pile is larger than the short pile. The bending moment of the long pile and short pile increases gradually with the increase in the number of short piles. When the combination changes from combination 1 to 3, the peak moment of the long pile and short pile increases by 15.8% and 15.2%, respectively. The maximum displacement is near the pile top, combination 3 has the largest horizontal displacement, and the peak displacement of the long pile and the short pile is 17.21 mm and 17.87 mm, respectively, but almost no effect exists on the horizontal displacement below the excavation bottom. In addition, reducing short pile length and increasing pile spacing will increase bending moment and horizontal displacement of the long and short piles to a certain extent, and this phenomenon is mainly concentrated above the excavation bottom, the influence of short pile length and pile spacing on surface settlement and excavation bottom heave can be ignored.

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