Determination of lifting force and displacement control method for active underpinning of pile foundation of super statically indeterminate bridge

Abstract

Disclosed is a lifting-force determination and displacement control method of active underpinning of statically indeterminate bridge pile foundations. The method includes: determining the underpinningdesign of a statically indeterminate bridge and setting ground pre-supported roof measures at the position of a pier corresponding to an underpinning bridge pile; determining the required lifting force in underpinning; during underpinning, digging earthwork downward to the bottom elevation of an underpinning bearing platform, performing mechanical construction of pile underpinning at the positionof the bottom elevation of the underpinning bearing platform, and after completion of the pile underpinning, performing construction on the underpinning bearing platform; arranging a jack for activelifting between an existing bearing platform and the underpinning bearing platform; after lifting force is determined for active underpinning, cutting off the underpinned bridge pile between the bearing platform and the underpinning bearing platform, and pouring and sealing concrete to complete active underpinning. Therefore, the size of the lifting force during the active underpinning process ofthe statically indeterminate bridge pile foundations can be determined accurately, deformation of the statically indeterminate bridge pile foundations during active underpinning is effectively controlled, and more accurate force conversion and deformation control is realized.

Description

technical field [0001] The invention relates to the technical field of pile foundation underpinning of super-statically indeterminate bridges, in particular to a method for determining jacking force and displacement control in the process of active underpinning of super-statically indeterminate bridge pile foundations. Background technique [0002] With the vigorous development of urban rail transit, there are more and more cases where interval tunnels cross railways, highways, municipal bridges and building pile foundations, and it is necessary to underpin the pile foundations within the influence range of the interval. Pile foundation underpinning can generally be divided into active underpinning and passive underpinning. Active underpinning means that before the original piles are unloaded, loads are applied to the new underpinning piles and the underpinning system to partially eliminate the space-time effect of the long-term deformation of the underpinned system, and the...

AI Technical Summary

Problems solved by technology

Therefore, the active underpinning method is generally adopted. The active underpinning process can be controlled by two methods: jacking force control and jacking displacement control, but the actual operation of jacking displacement control is very difficult. There is a certain displacement, but because of the vehicle load on the bridge surface (including impact), the self-weight of the bridge deck structure, the self-weight of the bridge pier, the self-weight of the cap, the self-weight of the bridge pile, and the negative friction resistance between the bridge pile and the soil are very large, resulting in the jacking The underpinning force required for displacement control is very large, which may easily lead to problems in the punching and local pressure bearing of the old cap, so the active underpinning of pile foundations in actual projects is generally based on jacking force control

[0004] For statically indeterminate bridges, due to factors such as uneven settlement of bridge piles and concrete creep during the long-term use of the bridge, the internal forces of the superstatically indeterminate bridge will redistribute, so that the load value transmitted from the bridge deck to each pier and Theoretical calculations are quite different. If the theoretically calculated jacking force is used for active underpinning of the pile foundation, it is easy to cause the bridge force to be inconsistent with the actual situation, so that the internal force redistribution of the statically indeterminate bridge will be redistributed again, and this time the internal force redistribution The process is short, and it is very easy to cause large deformation or cracks in the bridge structure

Therefore, for statically indeterminate bridge structures, it is difficult to accurately determine the jacking force during active underpinning of pile foundations.

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