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The HongKong-Zhuhai-Macau Bridge-Island-Tunnel (HZMB) Project

The HongKong-Zhuhai-Macau Bridge-Island-Tunnel (HZMB) Project The HongKong-Zhuhai-Macau Bridge-Island-Tunnel (HZMB) Project

The HongKong-Zhuhai-Macau Bridge is a super giant sea crossing linking Hong Kong, Zhuhai and Macau.  It is a 55-kilometre bridge tunnel system, including the 35.578-km Main Bridge- the largest part of the HZMB project, and a 6.75-km undersea tunnel. It is the longest sea crossing fixed link on earth.
We, Rapid Scaffold, are proud of being one of the contractors of the HZMB project: formwork installation and demolition in the thrust section.

Project Review

The western artificial island is situated at the waters of Lingdingyang. The thrust section was set by submerging immersed tunnel at the junction of island and tunnel in order for pipe docking conditions and construction working surface at sea. Starting and ends stake was K12+588~K12+639.700, and longitudinal gradient 2.98%. Due to structural and functional differences, the thrust section was divided into two parts: 23.7m CW1 & 28m CW2. Between the two parts set a 0mm-width wall expansion joint. The thrust section adopted single-box-double-chamber gallery box and single-box-four-chamber gallery box structure: 150, 130cm-thick for roof, 150cm for floor, 150cm side wall and 80cm middle wall.

Natural conditions

Situated in the western artificial island, the construction area was less affected by winds and waves under the cover of steel cylinders and wave proof walls. It was also less influenced by geology: before formwork installation and support erection, the western artificial island pit was carried out by the combined preloading of dewatering and loading while the foundation was well consolidated, C20 concrete hardening was performed after excavation of foundation pit of tunnel.
However, it was mainly affected by disastrous weather including tropical cyclones, rain storms, tornadoes, lightning strikes, short thunder storms. Intensive, frequent and disastrous, tropical cyclone was one of the most threatening natural disasters that influenced the process of engineering construction.

Analysis of engineering characteristics and difficulties

1. Interference factors:

The western artificial island thrust section tunnel was designed to last for 120 years. Hence structural waterproofing is extremely demanding. There in the buried structure should be many waterproof, water stopping ancillary facilities, and various embedded parts. In the process of template design, each interference factor should be considered therefore.

2. Large-scale formwork:

The external side wall molding reached maximum height 815cm, a quite high height. The maximum span of the thrust chamber is 14.55m, clearance height 8.4m, roof thickness 1.54m (max), load 4T per square meter. The design of formwork and support system should meet the requirements of construction scale to ensure the safety of the construction process.

3. Difficult installation:

The thrust section is a cast-in-place tunnel structure of deep foundation pit in offshore area. Due to the narrow working surface in the foundation pit, the effective working space is very limited. Therefore, the convenience of disassembly needs to be taken into consideration in ringlock scaffolding formwork design, especially for the overall assembly and overall disassembly.