The deformation of retaining piles and ground surface under various support systems during deep excavation

Background: Since the high-rise buildings and deep underground structures dramatically increases in urban area, the decent design and construction of deep excavations is essential before these structures are actually built up. The building area is very susceptible to the changes of their geo-environment, and even minor insecurity of a deep excavation may lead to a catastrophic failure of structures and deformation of the ground. Therefore, the adverse influence of deep excavation on the surrounding environment should be monitored and controlled stringently. Results: Based on the real case of deep excavation in Xuzhou, China, a FDM numerical model, which was accomplished by FLAC-3D, was developed to evaluate the deformation of retaining piles and ground surface under various excavation support systems. The original pile-anchor support system was simulated as well as the proposed quincunx double-row piles support system. For the original support system, the deformations were discussed by comparing the numerical results with monitoring data. For the proposed support system, orthogonal tests were designed to evaluate the influence of multiple factors on the effectiveness of excavation support. The optimum solution for the proposed support system was obtained through orthogonal tests. Conclusion: Results show that the pile space is the primary factor for the excavation-induced deformations, which can be reflected by the lateral displacement of retaining piles and the settlement around the excavation, while the row space has insignificant influence on the deformations. The conclusions of this paper can contribute to the design of similar projects and avoid excessive deformation of the ground during excavation in the future.