Study on the Global Deformation of a Combined Pile-Anchor-Strut Supporting System in Foundation Pit Excavations

The combined pile-anchor-strut supporting system is widely employed in deep foundation pit excavations due to its effectiveness in deformation control. However, the complex interaction mechanisms among its various components present significant challenges for theoretical analysis. This study proposes a novel analytical approach to predict the global deformation behavior of this composite supporting system. By establishing the total potential energy expression for the structure, incorporating the capping beam, internal struts, supporting piles, anchor rods, and waling beams—with particular emphasis on the critical effect of prestress loss—and applying the principle of minimum potential energy, an explicit analytical solution for the maximum horizontal displacement at the pile top is derived. The proposed method is validated through a case study of an actual foundation pit project. Comparison with field monitoring data and numerical simulation results demonstrates that the theoretical maximum horizontal displacement at the pile top shows relative errors within acceptable limits compared to both measured and simulated values, indicating high computational accuracy. Moreover, the overall horizontal displacement curve of the supporting system obtained from the theoretical solution shows close agreement with field monitoring data. The results confirm that the proposed method, characterized by clear physical concepts and consideration of prestress loss, provides a reliable and practical theoretical tool for deformation analysis and design optimization of combined pile-anchor-strut supporting systems.