English：

To investigate the safety and stability of the bridge after the shield tunnel underpasses throughthe pile foundation underpinning reinforcement, taking the shield crossing sequence and the shield tailgrouting pressure as the key parameters, the numerical model is established by Plaxis3D software toexplore the influence of the two on the settlement of the bridge. The effect of train vibration load on thesettlement of the bridge and the soil under the bridge during the subway operation period was simulated.The results indicate that the settlement of double⁃line crossing is the largest, and the single⁃line crossingis more conducive to controlling the settlement, and the effect of crossing the left line first is the best. Thegrouting pressure is negatively correlated with the settlement. The maximum settlement of the bridge is only0. 86mm when the left line is first crossed with a grouting pressure of 300kPa. During the operation periodof the subway, the single settlement peak of the train vibration is 3. 85 × 10-3 mm, and the maximumsettlement of the soil under the pile cap during the 30 years operation period is 39. 86×10-3 mm, and theinfluence is controllable.