Mechanical Behavior Analysis of Excavation and Retaining Piles in Gravel Formation along Adjacent Railways: A Comparative 3D FEM Study with Monitoring Data

Carrying out underground excavation work with retaining pile supports adjacent to a running railway is a risky and cautious job. To evaluate the safety and practicability of underground excavation, a three-dimensional finite element program was developed and used in this study to simulate and analyze the mechanical behavior of the gravel layer in response to excavation to serve as the design for retaining piles as supports. Monitoring instruments (such as inclinometers and subsidence observation points on railway track surfaces) were installed during construction to provide immediate monitoring of the excavation area and information for safety assessments. The calculation process in the numerical analysis included the execution of programs such as pre-processing, central calculation, and post-processing, as well as the simulation of construction steps, such as the initial stress of gravel layer, railway vehicle load, layered excavation, and support installation. By comparing the results of 3D finite element analysis with monitoring data, it was found that the construction method of excavating the gravel layer near the adjacent railway and supporting it with retaining piles provides a reliable engineering technology. The results of the comparative analysis were all within a safe range and showed a consistent trend.