“Billion-Dollar Mountain Tunnel Wonder Ahead of Schedule by 6 Months: World-Leading Special Techniques by Son Hai”

Doc San Tunnel Ahead of Schedule by 6 Months

The Nha Trang – Cam Lam section of the North-South Expressway officially opened on May 19, 2023, recognized as one of the earliest completed projects nationwide. Among its key components, the Doc San Tunnel stands out, finishing six months ahead of schedule. This achievement symbolizes the exceptional organizational and technical innovation capabilities of Vietnamese contractors.

Spanning over 49 km, the Nha Trang – Cam Lam expressway, with a total investment of 7.6 trillion VND, passes through Dien Khanh district, Cam Lam district, and Cam Ranh city (Khanh Hoa province). The early completion of the tunnel has significantly reduced travel time, enhancing regional connectivity and tourism in the South Central Coast region.

The Doc San mountain tunnel, part of construction package No. 3 with a total investment of 1.2 trillion VND, is managed by the Ho Chi Minh Road Project Management Unit, with Son Hai Group as the investor and contractor. Construction began in November 2021, with a total length of 1,480 meters, comprising two parallel tunnels, each over 700 meters long.

To expedite the project, the investor mobilized over 1,500 workers and 500 specialized pieces of equipment, operating at four drilling sites around the clock. The average drilling rate reached 10 meters per day, with the tunnel breakthrough achieved in May 2022, six months ahead of schedule.

Speaking to Khanh Hoa Newspaper, Mr. Nguyen Van Huy, Deputy General Director of Son Hai Group, stated: “The company applied the Austrian NATM tunneling method, a leading global technology, to construct the Doc San Tunnel. To complete this section, we mobilized hundreds of employees and modern equipment, working in three shifts, four teams. As a result, the tunnel was completed in May 2022, six months ahead of the approved schedule.”

Application of NATM – A Leading Global Tunneling Solution

Son Hai Group implemented the Doc San Tunnel using the New Austrian Tunneling Method (NATM) from Austria, renowned as a leading global tunneling technology. NATM is a widely adopted underground construction method, distinguished by its advancements in shotcrete technology.

NATM optimizes the self-supporting capabilities of the terrain, making it one of the most economical and efficient techniques for tunnel construction. It also reduces material and labor costs while shortening project timelines.

Particularly, NATM is highly effective in withstanding geological pressures in high seismic risk areas. This method has become the primary solution for constructing numerous road tunnels worldwide.

The Doc San Tunnel construction team from Son Hai Group, with extensive experience in mountain tunnel construction across various locations, ensured the tunnel’s early completion.

Additionally, the tunnel’s geological characteristics, primarily consisting of hard rock with no soil mixture, facilitated the drilling, blasting, rock removal, and shotcreting processes, adhering strictly to technical procedures.

Notably, unlike other road tunnels (typically paved with concrete), Son Hai Group proposed to the Ministry of Transport to use asphalt for the entire tunnel road surface. This innovation has led to several breakthroughs.