At the starting point of the Maritime Silk Road, a “dragon” – the Hong Kong-Zhuhai-Macao Bridge (HZMB), stretches into the distance, dividing the ocean into two parts.
Reputed as “the eighth wonder of the 21st century", the HZMB officially opened on the morning of October 24th. The bridge links three areas, making it much more convenient to travel from one area to another. Since opening, the three-hour drive between Hong Kong, Zhuhai and Macao has been shortened to 30 minutes.
The project involves more than 400 new patents, breaking 7 world records, including the overall design and key techniques which were independently developed. In 8 years, the Hong Kong-Zhuhai-Macao Bridge has fulfilled the dream of generations and amazed the whole world with the perfection and the Chinese standard of 120 years of service life. From the Belt and Road Initiative to "Created in China", there is always a group of people behind the scenes providing strong technical support for the country. From the beginning of the construction in December 2009 to the day of the official opening, a large number of Tianjin University people, TJU teachers, students and alumni, have participated in the design and construction of the HZMB, contributing the "Wisdom of TJU".
The floor plan of the artificial island
Professor Wang Yuanzhan on HZMB
The main bodies of the HZMB project consist of the cross-sea bridges and one undersea tunnel, as well as artificial islands connecting the bridges and tunnel, which are the key projects in the HZMB construction. Engineers faced a daunting task with the design and construction of the bridge-tunnel section of the project when taking into account the transitions between above ground and undersea areas. The stability of the island wall under the influence of hydrostatic pressure and waves and the seepage analysis for the island pit were the main problems to be solved in the construction of the bridge-tunnel. The CCCC-FHDI Engineering Co., Ltd was in charge of the design of the artificial island, adopting an embedded steel large cylindrical structure in building the island wall. This structure is a new type of coastal engineering structure for which China has not yet formulated norms. Entrusted by CCCC-FHDI Engineering Co., Ltd, the team led by Professor Wang Yuanzhan analyzed the stability and seepage in the artificial island pit, solved such technical problems as the weakening of the soft soil under the wave load and the simulation of the failure process of the embedded steel large cylindrical structure and carried out calculations to analyze the stability and seepage under various load cases, providing technical support for the artificial island design.
The photo of the installation ship and the immersed tubes for shipment after being connected to each other in the deep-water dock
The three-dimensional fine finite element simulation consisting of the installation ship, immersed tubes, cables and water system
Associate Professor Xiao Zhong
The undersea tunnel of the HZMB consists of 33 immersed tubes, the weight of each being nearly 80,000 tons, which is the same as the weight of a medium-sized aircraft carrier, and the cost being up to 100 million yuan. Having been prefabricated in the deep-water dock, the immersed tubes need to be connected to the installation ship with cables, which then towed it to the construction site during the appropriate period with acceptable wave and load conditions. The safe floating and sinking of the immersed tubes was crucial to the safe construction of the whole project. In order to assist the design and construction unit in solving this problem, the engineering team launched a research project “the numerical simulation of the floating of the sinking tube under the combined actions of wave and flow” under the charge of Associate Professor Xiao Zhong of the School of Civil Engineering of Tianjin University, establishing for the first time the 1:1 three-dimensional fine finite element simulation model consisting of the installation ship, immersed tubes, cables and water system taking the viscidity and turbulent characteristics of the water and the coupling among the installation ship, immersed tubes, cables and the water into consideration in the calculation model.
In order to make the simulation model better serve the project, the research team went to the engineering site to conduct on-site inspection of the final floating scheme of the immersed tubes, carried out numerical simulations for dangerous conditions, and offered instructions to ensure safety, provided guidance for safe construction during the floating and sinking process. The research results of this project can provide theoretical guidance for subsequent similar projects, and the economic benefits are remarkable.
The prefabricated pier of the HZMB fixed to the semi-submerged barge
The prefabricated pier of the HZMB transported by the semi-submerged barge
The parts for the piers of the HZMB were prefabricated separately on land and installed on water; the largest part weighed 3510 tons and was over 22m in height. The prefabricated piers were transported to the construction area by semi-submerged barge. The long towing distance, the complicated sea conditions, the tall and slender structure of the piers and the high center of gravity of the system led to a problem — the semi-submerged barge and the pier joint moved under the influence of the wind and waves during the transport process, and the trolley wheels supporting the piers were subjected to heavy loads. To ensure the safety of the semi-submerged barge and bridge piers, the team led by Professor Bie She'an of the School of Civil Engineering of Tianjin University carried out the calculation of hydrodynamic property of the whole system and the analysis of the towing stability of the bridge piers. Based on this, the team also put forward a scheme of fixing the piers on the transport ship so as to ensure the safe transportation of the piers.
Many alumni of Tianjin University have contributed to the design and construction of the HZMB, overcoming a number of difficult problems and completing many tasks—solving the sinking of the immersed tubes and silting problems; pioneering multiple methods of rapid sinking of steel cylinders; successfully finishing the design of the Guishan Plant to prefabricate the immersed tubes of the HZMB; calculating the stability of the embedded steel large cylindrical structure by the Plaxis 3D software; completing the task of designing the track on the fabrication yard for the immersed tube.
