The 6.7 km undersea tunnel is a key component of the large-scale Hong Kong-Zhuhai-Macau Bridge (HZMB) project, which connects Hong Kong, Zhuhai, and Macau via a system of artificial islands and bridges. Construction of the tunnel was completed in the summer of 2017. HZMB is a 6.7 km long underwater tunnel.
The technical complexity of the structure is considered to be very high. In addition to the issue of ventilation for a long road tunnel, it was necessary to resolve issues related to the manufacture, subsequent assembly, and transportation by sea of large sections of the “tube,” as well as the connection of these sections under high water pressure.
The tunnel consists of 33 cylindrical sections connected by butt joints. Each section is 180 m long, 38 m wide, and 11.4 m high, and weighs about 80,000 tons.
The tunnel was built under the surface of the Lindiangyan Canal, which is part of the Pearl River Delta, or the Pearl River, the third largest river in China. The purpose of including a deep underwater tunnel in the transport chain is to ensure the passage of 300-ton tankers, which often travel along this sea route for economic reasons.
This circumstance causes additional difficulties in the design process. In particular, specific impacts on the construction site are possible, such as the fall of a tanker anchor weighing up to 22 tons. The speed at the moment of impact will be 9 m/s. The tunnel must even withstand the weight of a sunken ship. Protection against the effects of seismic activity and explosions is also provided.
The tunnel is located at a depth of 48 meters and must withstand large amounts of water and soil. Taking into account the very difficult unstable soft soils and aggressive marine environment, only the most advanced projects that met all safety requirements were allowed to participate in the competition. At the same time, the estimated service life is set at 120 years.
In addition, a new comprehensive system for regulating and organizing road safety in tunnels was created for this project, which will be applied in the construction of other projects.
Today, HZMB is one of the world’s largest infrastructure projects—the bridge has become the longest bridge over the sea, with a total length of 29.5 km, including 22.9 km of the bridge itself and 6.7 km of a double six-lane underwater tunnel connecting the artificial islands.
The construction of this part of the transport link was officially completed on July 7, 2017. The total length of all transport links, including the beam bridge, cable-stayed bridges, islands, and tunnel, was 55 km. The construction was completed in December 2017, and the project was put into operation in early 2018.
The project took almost seven years to complete, but thanks to its implementation, travel time within one of Asia’s most economically active regions has been significantly reduced. For example, it now takes half an hour to get from Hong Kong to Zhuhai instead of three. In today’s world, such time savings cannot be overestimated.