The Hong Kong-Zhuhai-Macao Bridge, formerly known as the Lingdingyang Bridge, is a super-large cross-sea passage connecting Hong Kong, Zhuhai and Macao, with a total length of 55 kilometers, of which the main project "bridge and tunnel in the sea" is 35.578 kilometers long, and the undersea tunnel is about 6.75 kilometers long. The designed service life cycle is 120 years, and it will become the world's longest cross-sea bridge after completion. Hong Kong-Zhuhai-Macao Bridge adopted the world's first prefabricated cap pier overall design, lifting construction method, buried cap, steel pipe composite pile design concept.

Second, the structure design of the lower part of the non-navigable bridge in shallow water area

2.1 Prefabricated pier structure design and key structure

The non-navigable pass bridge in shallow water area adopts 85m span block segment composite continuous beams, and the pier body adopts prefabricated assembly scheme. The pier body adopts rectangular hollow pier, the interior is provided with a longitudinal web, and the chamfer is arranged around the pier body. In order to adapt to the separate main beam arrangement of the superstructure, the pier is gradually widened horizontally from 6m below the top of the pier to 23.5m at the top of the pier, forming a winged structure. In order to satisfy the stress of pier cap structure, prestressed steel bundles are arranged horizontally in pier cap. The pier body adopts wet joints, and the piers in the high pier area are provided with 2 joints. The first joint is arranged at elevation +8m, above the splash zone; The second joint is 8m from the top of the pier. The pier in the low pier area is provided with a total of 1 joint, which is set at the elevation +8m and is located above the splash area. The joint of the pier body is connected with the wet joint. Jacks are set at the wet joint to adjust the tilt caused by the installation of the cap and ensure the accurate position of the pier top plane. Construction operability is strong, and the wet joint of the pier is more reliable. The structural durability is strong, the structural dynamic performance is good, and the risk of corrosion or failure of the prestressed steel bundle is avoided due to the prestressed connection scheme. The precast retaining wall is set outside the cast-in-place wet joint concrete, which mainly considers the color difference between precast and cast-in-place concrete to improve the appearance of the pier.

2.2 Prefabricated cap structure design

In order to minimize the water resistance of the foundation, the foundation of the non-navigable pass bridge of the Hong Kong-Zhuhai-Macao Bridge is prefabricated by buried bed method. The prefabricated cap technology reduces the construction difficulty, speeds up the construction progress, and improves the durability of the foundation. The plane size of the bearing table in the high pier area is (16.8*12.1) meters (cross bridge * longitudinal bridge). The thickness is 4.5 meters, and the corners are rounded to facilitate the release of molds. The prefabricated part of the cap is made of C45 Marine durable concrete; The cast-in-situ part is made of C45 micro expansion Marine durability concrete. Base block and cap are prefabricated together. The maximum weight of the cap and the bottom pier in the high pier area is 2650T. The prefabricated cap adopts four-point hoisting, and the lifting points are arranged in the four corner pile holes on the cap. The local structure of the lifting points is reinforced concrete structure, which is made together during the prefabrication of the cap.

2.3 Durability measures for precast pier and cap

High-rise +0.8m, precast pier concrete only external surface with silane impregnation for anti-corrosion coating. The top and sides of the prefabricated cap are coated with silane impregnation, which makes the surface have low water absorption and low C1-permeability. The outer vertical main reinforcement and outer ring stirrup are made of stainless steel reinforcement in the splash area and below (high-rise +0.8m below).

Iii. Concluding remarks

The construction of the bridge will promote the integrated economic development of Guangdong, Hong Kong and Macao, and enhance the comprehensive competitiveness of the Pearl River Delta. The design life of the main project of the Hong Kong-Zhuhai-Macao Bridge will reach 120 years, and the construction of the non-navigable bridge in the shallow water area will adopt the design scheme of "large-scale, industrial, standardized and assembled". At the same time also carried out the prefabricated cap pier overall design, lifting, buried cap, steel pipe composite pile design concept and many other technical innovation, which belongs to the history of bridge construction one of the world's leading topics, rich and perfect our bridge design, construction technology, has important theoretical significance and engineering application value.