Maintenance of Pier and Abutment Foundations

The purpose and task of maintaining the piers and abutments of masonry, concrete, and reinforced concrete bridges are to keep the structures intact, stable, free from tilting, reduce traffic vibration, and mitigate foundation scouring. Adhering to the principle of "prevention first, combination of prevention and control", bridges should be regularly inspected and maintained to ensure safe use. According to the regulations of relevant maintenance technical specifications, the main work contents of pier and abutment maintenance are as follows:

• The surfaces of piers and abutments must be kept clean, and moss, weeds, thorns, and dirt should be removed in a timely manner.

• When the mortar joints of masonry structures fall off due to long - term exposure to the atmosphere and rain erosion, re - pointing should be carried out.

• When the concrete surface suffers from erosion, spalling, honeycombing, and pitting, the surrounding area should be cleaned in time and smoothed with cement mortar.

• When the facing parts of masonry structures are severely weathered and damaged, they should be replaced. Repairs with stone or precast concrete blocks are required to have a color and texture basically consistent with the original masonry.

• If the top surface of the pier and abutment of a beam - type bridge has no drainage slope, or the slope is uneven and cracked, cement mortar or concrete should be laid in time to form a transverse slope for drainage.

For the enlarged foundations of medium - and small - sized bridges made of concrete or grouted rubble, their defects often include scouring under the foundation and loose and cracked foundations. When there is displacement or inclination of the bridge piers and abutments, or when the end - top displacement under live loads is relatively large, the foundation may often be diseased and needs to be inspected by excavation. When the cofferdam can prevent water or the riverbed is dry, the foundation can be directly dug for inspection. For shallow - water piers and abutments in water with a low flow rate, inspection can be carried out by pumping water after setting up a cofferdam, and laser detection methods can also be used to inspect diseases such as scouring, cracking, and fracture of pier and abutment foundations.

Reinforcement of Pier and Abutment Foundations

Common methods for foundation strengthening include the enlarged foundation method, the supplementary pile foundation method (driven piles or bored - cast - in - place piles), and artificial foundation strengthening (improved foundation method), etc. Common methods for strengthening piers and abutments include strengthening piers and abutments with through - cracks using reinforced concrete hoops or sheaths, dealing with pier and abutment slippage by building additional retaining walls, and strengthening bridge structures with excessive settlement by jacking - up methods. This article explores the enlarged foundation strengthening method, which is applicable when the foundation bearing capacity is insufficient or the embedment is too shallow, and the piers and abutments are rigid solid - type foundations made of masonry or concrete. The enlarged foundation bottom area should be determined by checking the foundation strength. When the foundation strength meets the requirements but the defect is only manifested as excessive uneven settlement deformation, the enlarged foundation bottom area for strengthening is mainly selected based on the calculation of foundation deformation. The enlarged foundation strengthening method can be carried out in the following order:

1. Usually, sheet - pile cofferdams are first driven within the necessary widening range. If the soil at the pier and abutment foundation is poor, necessary reinforcement should be carried out.

2. Excavate the soil inside the cofferdam until the necessary depth is reached (pay attention to the safety of the piers and abutments).

3. After draining the water inside the cofferdam, lay stones (grouted) or make a concrete foundation.

4. Pay attention to the firm combination of the new and old foundations. During construction, tie - bar (anchor) reinforcement can be added or steel pins can be inserted to firmly integrate the strengthened and enlarged foundation with the old foundation into a whole.

Conclusion

Piers, abutments, and foundations are important components of a bridge. The maintenance of the bridge substructures should be further enhanced. Great efforts should be made to do a good job in the maintenance of the bridge substructures, actively discover the disease defects of the bridge, analyze the possible causes at the same time. On the premise of mastering the causes, take effective reinforcement and maintenance countermeasures to reduce or eliminate the diseases.