5.2.2. Underpinning Pile Unloading Stage

As shown in Figure 12, during the unloading process of C15, the force from the jack becomes smaller, and the load transfer is gradually realized. The settlement of the bridge pier and the underpinning beam gradually increases, but the change of the displacement tends to be stable after the unloading of the jack is completed. There is no sudden change in displacement during the process, indicating that the construction plan is reasonable in the unloading stage. During this period, the maximum change rate of pier settlement is -0.01 mm/h, and the final cumulative maximum value is −0.04 mm. The maximum change rate of pier inclination angle is 0.003◦/h, and the final cumulative maximum value is 0.007◦. The maximum change rate of underpinning beam settlement is −0.04 mm/h and the final cumulative maximum value is −0.09 mm. The settlement and inclination of the bridge superstructure are within the safe range.
