Experimental and Numerical Study of Braced Retaining Piles with Asymmetrical Excavation

In this study, asymmetrical and symmetrical pile length model tests were performed to investigate the interaction between retaining piles with asymmetrical excavation. The deformation, earth pressure, and bending moment of the retaining pile on both sides were measured during asymmetrical excavation. The numerical analysis using PLAXIS 2D was validated by comparing the results with experimental data. Through numerical studies, the horizontal displacement, bending moment, and earth pressure of the piles were studied with asymmetrical excavation in terms of three design factors: asymmetrical pile length, pile stiffness, and bracing stiffness. Results show that asymmetrical excavation induces a “push-back effect”, and the pile-top displacement on the shallower side decreases from 0.54 mm to 0.49 mm and from 0.47 mm to 0.42 mm for asymmetrical and symmetrical pile lengths, respectively. The deformation, earth pressure, and bending moment of the retaining pile develop asymmetrically during asymmetrical excavation. The lateral earth pressure distribution was closely related to pile deformation, while the pile bending moment was related to the lateral earth pressure and the axial force of the bracing. With a decrease in the retaining pile stiffness and an increase in the bracing stiffness, the deformation mode of the retaining pile transitioned from a cantilever type to a bulging type, which further influences the distribution of earth pressure on the retaining pile and the distribution of the pile bending moment. For asymmetrical excavation, a deformation-based asymmetrical design for the retaining pile length is recommended to make good use of the push-back effect.