Effects of Large-Diameter Shield Tunneling on the Pile Foundations of High-Speed Railway Bridge and Soil Reinforcement Schemes

In order to study the effects induced by large-diameter shield tunneling on the internal force and displacement of adjacent high-speed railway bridge pile foundations, symmetrical element analysis models for the whole process of large-diameter shield tunneling through the high-speed railway bridge were established. The protective effects of various soil reinforcement schemes such as isolation piles' protection, Metro Jet System (MJS) reinforcement, and the addition of isolated piles' crown beams were investigated. The numerical results show that the maximum bending moment and the maximum lateral displacement of the bridge piles appear at the piles' body of the central elevation of the tunnel and the piles' top, respectively. Without any soil reinforcement measures, the maximum lateral displacement and settlement of the piers top were 7.1 mm and -7.2 mm respectively, which could not meet the displacement control requirements of +/- 2 mm for the piers of the existing bridge under the condition of the normal operation of high-speed trains. The isolation piles' protection effect was better than that of MJS reinforcement alone. Two or more soil reinforcement measures could be adopted simultaneously to further control the displacement of piers within +/- 1 mm. The validity of the numerical simulation results was verified by comparing them with the field monitoring results.