‘4000-Day Undersea Journey’ Hyundai Construction Completes Korea’s Longest Boryeong Undersea Tunnel

World's 5th Longest & Korea's Longest 6.9km Boryeong Undersea Tunnel Opens After 11 Years
Total Construction Period About 4,000 Days, Battle Against Seawater Inflow 80m Undersea Tunnel

Interior view of the completed Boryeong Undersea Tunnel / Provided by Hyundai Engineering & Construction.

[Asia Economy Reporter Jo Gang-wook] Hyundai Engineering & Construction announced on the 30th that it will open the ‘Boryeong Undersea Tunnel,’ the longest domestic tunnel of approximately 6.9 km connecting Daechun Port in Boryeong City, Chungnam Province, and Wonsan-do in Ocheon-myeon, Taean-gun.

The Boryeong Undersea Tunnel is a project worth 488.1 billion KRW, involving about 4,000 days of construction and approximately 800,000 person-days of labor. With a total length of 6,927 meters, it is the longest tunnel in Korea and the fifth longest tunnel in the world. This tunnel is a two-lane road that passes about 80 meters below sea level from Taean (upbound lane) to Boryeong direction (downbound lane).

The tunnel construction began in December 2010 with the purpose of connecting the disconnected National Route 77 near Daecheon Beach to Yeongmok Port on Anmyeon-do. The upbound lane was completed in February 2019, and the downbound lane was connected by aligning the centerline in June 2019.

The NATM (New Austrian Tunneling Method) involves drilling holes into solid rock and blasting explosives to excavate the rock. Hyundai Engineering & Construction enhanced excavation accuracy by applying this method along with advanced robot drilling machines controlled by computer positioning.

To effectively control the biggest risk of undersea tunnel construction, seawater inflow, Hyundai Engineering & Construction applied the blasting-type NATM method for the undersea section and optimized the excavation method through geological analysis using 3D computing, successfully tunneling through the center without a single seawater leakage.

The 3D geological analysis revealed many hazardous sections requiring caution, such as weak coal-bearing layers and folds (bent geological structures). To ensure safety, special waterproof doors with a thickness of 1 meter were installed throughout the tunnel to allow workers to evacuate in emergencies, along with continuous monitoring of these sections.

Additionally, to minimize damage to surrounding facilities caused by construction, the IMG (Intelligent Multi Grouting) method was applied. This method precisely controls the optimal pressure, flow rate, and timing of cement slurry during tunnel wall concrete construction, fundamentally blocking seawater inflow inside the tunnel.

To enhance the durability of the Boryeong Undersea Tunnel, Hyundai Engineering & Construction increased the original wall thickness from 30 cm to 40 cm and upgraded the concrete strength from normal (24 MPa) to high strength (40 MPa). Corrosion-resistant rock bolts were applied at connection sections to further improve safety.

Exterior view of the completed Boryeong Undersea Tunnel / Provided by Hyundai Engineering & Construction.

With the opening of the Boryeong Undersea Tunnel, the travel time from Boryeong Daechun Port to Taean Yeongmok Port, which previously took 1 hour and 30 minutes, has been reduced to 10 minutes. This will facilitate smoother logistics processing and enable sufficient supply of electricity, telecommunications, and water, thereby improving the regional economy and living conditions for nearby residents.

A Hyundai Engineering & Construction official stated, "Undersea tunnel construction is a 24/7 battle against seawater. Without the accumulated know-how and experience from civil engineering projects completed worldwide by Hyundai Engineering & Construction, we would not have overcome the challenge of seawater inflow." He added, "Just as we completed the longest domestic Boryeong Undersea Tunnel with the highest quality contributing to the revitalization of the West Coast economy, we will do our best to satisfy customers in future projects."

Meanwhile, the opening ceremony of the Boryeong Undersea Tunnel held on the same day was attended by political and government figures including the Prime Minister, the 2nd Vice Minister of the Ministry of Land, Infrastructure and Transport, the Governor of Chungcheongnam-do, and the Director of Daejeon Regional Land Management Office, as well as Hyundai Engineering & Construction executives, partner company representatives, and local residents. The event proceeded with a project progress report, a welcome speech by Prime Minister Kim Boo-kyum, congratulatory remarks by Chungnam Governor Yang Seung-jo, and an opening ceremony led by Hyundai Engineering & Construction President Yoon Young-joon and other distinguished guests.

This content was produced with the assistance of AI translation services.