On July 15, the "Central Enterprises Marine Engineering Technology Innovation Consortium," led by China Communications Construction Company Limited, was established in Beijing.

At the founding conference that day, Jian Zhimin, an academician of the Chinese Academy of Sciences; Ou Jinping, an academician of the Chinese Academy of Engineering; and Zhang Xigang, an academician of the Chinese Academy of Engineering, delivered keynote reports titled "Deep-Sea Engineering and Technological Development," "FRP for Offshore Floating Buildings, Towns, and Energy and Other Infrastructure," and "Bridge Engineering—From Shallow Sea to Deep Sea," respectively. They analyzed the current state of deep-sea exploration around the world and, from their respective fields, introduced China's **research and fruitful achievements in deep-sea exploration.

　　Installing Human Eyes on the Seabed

Oceans cover 71% of the Earth's surface, of which the deep sea accounts for 60%, with an average sea depth of 3,700 meters. Since the 20th century, scientists have been exploring the deep sea, examining such matters as the deep sea's impact on global climate change, deep-sea metal minerals, and the biosphere deep within seabed strata.

There are three major technological means of exploring the deep sea: deep drilling, deep diving, and deep networks. "Ocean drilling has a history of 56 years so far, with 22 countries participating jointly. It is the largest, longest-running, and most accomplished international big science program in the fields of Earth science and marine science and technology, bringing together the world's highest level of marine scientific and technological strength," Jian Zhimin said in his report "Deep-Sea Engineering and Technological Development." At present, there are more than 4,000 boreholes across the world's major oceans, with more than 400,000 meters of core samples recovered.

According to the introduction, China joined ocean drilling in 1998 and designed and led four South China Sea ocean drilling expeditions, establishing China's international scientific leadership in deep-sea research in the South China Sea and providing important theoretical support for the exploration and development of deep-sea oil and gas resources in the South China Sea.

Jian Zhimin disclosed that Chinese scientists are currently building a seabed scientific observation network, constructing thousands of kilometers of submarine optoelectronic hybrid cables, feeding high-voltage electricity to the seabed, charging through seabed optoelectronic nodes, and transmitting information back through a combination of wired and wireless methods.

"We compare this project to installing human eyes on the seabed," Jian Zhimin said.

　　Building Floating Cities at Sea

In the report "FRP for Offshore Floating Buildings, Towns, and Energy and Other Infrastructure," Ou Jinping described offshore corridors, spatial expansion, and land-sea coordination as marine civil engineering.

In 2019, UN-Habitat proposed the concept of future floating cities at sea. In 2020, the annual report of the American Society of Civil Engineers mentioned two major future world trends: one is supercities, and the other is floating cities.

"Many countries already have corresponding concepts and plans and are gradually putting them into practice," Ou Jinping said, mentioning the "Blue Estate" floating city project of the U.S. company Ocean Estate. Located between Miami and the Bahamas, the project uses high-performance concrete modules and measures 1,500 meters long and 1,000 meters wide, with an area about half that of Monaco, and is expected to accommodate about 15,000 people. South Korea's "Busan on the Sea" city demonstration model, sited in Busan, South Korea, will have a total area of 62,700 square meters. In addition, to cope with sea-level rise, the Maldives' "floating city" has designed 5,000 floating units capable of housing 12,000 people.

In 2016, Ou Jinping set up a marine civil engineering team at Harbin Institute of Technology (Shenzhen) and has produced some floating offshore platform structures. Ou Jinping disclosed that the team is exploring and testing engineering challenges such as large offshore load-bearing floating body modules, how floating bodies are fixed to the seabed, and how seawater-sea sand concrete can resist corrosion.

　　Researching Deep-Sea Bridges with Longer Spans

In bridge construction, bridges in water depths of less than 60 meters are shallow-sea bridges, and bridges in water depths greater than 60 meters are deep-sea bridges.

According to the introduction, China has successfully built a number of sea-crossing bridge projects at home and abroad in water depths of less than 60 meters and with spans of less than 2,000 meters, achieving a series of technological advances in deep-water foundations, structural systems, disaster prevention and mitigation, longevity assurance, construction technology, and health operation and maintenance.

"As the throat project for realizing intercontinental and land-island connectivity, building deep-sea bridges is of great significance, but it also faces harsher construction conditions. To break through to larger bridge spans, the requirements for safe, long-life, and healthy operation and maintenance are higher," Zhang Xigang believes. These will all become technical challenges that future deep-sea bridges must face.

In the report "Bridge Engineering—From Shallow Sea to Deep Sea," Zhang Xigang disclosed that, for future cable-stayed bridges with a single span of 1,500 meters and suspension bridges of about 3,000 meters, the relevant team has begun researching new composite technologies suitable for water depths approaching 100 meters.

It is reported that the "Central Enterprises Marine Engineering Technology Innovation Consortium" was formed under the guidance of the Science and Technology Innovation Bureau of the State-owned Assets Supervision and Administration Commission of the State Council, with 10 leading marine engineering central enterprises as the core, together with 24 universities and research institutes with strengths in marine disciplines, including Tsinghua University, and 12 large enterprises and institutions and leading private enterprises, pooling superior resources.