An overall active underpinning structure and underpinning method for large-tonnage multi-pile foundations of bridges

Abstract

The invention provides an overall bridge large-tonnage and multi-pile-foundation active underpinning method. According to the method, an overall active underpinning structure needs to be provided. The method specifically comprises the steps that new piles, a longitudinal apron piece and a transverse apron piece are built, and a later-pouring node position is reserved on the longitudinal apron piece; a hoop is poured on an underpinned pile; ejecting and lifting force is exerted by the hoop so that the underpinned pile can be unloaded to zero axial force, and the underpinned pile is cut off; the underpinning node of later-poured reinforced concrete is built between the longitudinal apron piece and the underpinned pile, and stress conversion is finished; the steps are repeatedly carried out on each underpinned pile, and the overall active underpinning of all bridge pile foundations is finished. The invention further provides the overall bridge large-tonnage and multi-pile-foundation active underpinning structure. The number of the new piles needing to be arranged is small, and the difficulty that the piles cannot be arranged under the limitation of space is avoided. Differential settlement among the underpinned piles can be adjusted conveniently, and the stress performance and durability of the underpinned piles are reliable.

Description

technical field [0001] The invention relates to a pile foundation underpinning technology, in particular to an integral active underpinning structure and an underpinning method for a large-tonnage multi-pile foundation of a bridge. Background technique [0002] At present, the construction of rail transit projects represented by the subway in my country is in the ascendant, and in the process of subway construction, the spatial intersection of the section tunnels and the existing municipal bridges often occurs. At this time, the following two schemes are adopted: 1) Demolition and reconstruction of the bridge, so that the pile foundations of the new bridge are arranged to avoid the shield tunnels to be built; 2) Underpinning of several bridge pile foundations that have spatial intersections. The bridge demolition and reconstruction plan has a large investment and seriously affects the surrounding environment, and is rarely used at present, while the pile foundation underpinn...

AI Technical Summary

Problems solved by technology

[0005] 1) The traditional underpinning scheme adopts the structural form of two new piles plus a flat pole bearing platform beam for stress conversion, and the number of new piles required is twice the number of underpinned piles. If multiple pile foundations need to be underpinned at the same time , due to space constraints, it is often impossible to arrange the plane position of new piles

[0006] 2) The traditional underpinning scheme is used to underpin the multiple pile foundations of the bridge structure. If the upper loads borne by each underpinned pile are quite different, after the force transfer is completed, it is easy to produce a fault between the underpinned piles. Differential settlement, and then lead to adverse consequences such as cracking of the bridge superstructure

[0007] 3) The tonnage of the upper load borne by the bridge pile foundation is usually relatively large, and the underpinning node structure (whether passive or active) in the traditional underpinning scheme adopts tooth keys and planting bars to transfer between the old and new structures. The shear force has a small safety factor, which is very unfavorable to the durability of the bridge structure

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