Final 250 Meters of Vietnam Hydropower Tunnel Completed by Drill and Blast
The Thượng Kon Tum hydropower project in Vietnam has a water conveyance tunnel more than 17 kilometers long. A collapse in the fourth quarter of 2018 stopped its tunnel boring machine about 250 meters from the connection point. The remaining section was completed by drill and blast in the fourth quarter of 2019. The project connected to the national grid in 2021.
Construction of the Thượng Kon Tum hydropower project began in September 2009, with investment from CTCP Thủy điện Vĩnh Sơn – Sông Hinh. Its water conveyance tunnel is more than 17 kilometers long, including about 12 kilometers of circular tunnel with a diameter of 4.5 meters. The contractor used a tunnel boring machine supplied by Robbins, which began excavation in 2012. The original contractor’s work did not meet requirements, and it subsequently left the project.
In 2016, a consortium of Robbins and CTCP Xây dựng 47 took over repairs to the machine and construction of the remaining tunnel. Robbins said the equipment had deteriorated because of inadequate maintenance and the high temperatures and humidity inside the tunnel. Repairs began that March; the machine underwent trial runs in April and resumed excavation in June.
Image related to tunnel construction at the Thượng Kon Tum hydropower project. Photo: Robbins.（VietVance）
The rock encountered during construction was harder than earlier surveys had indicated: surveyed granite had a compressive strength of about 120 MPa, while the rock encountered averaged 270 to 290 MPa, with some samples reaching 300 MPa. Robbins said hot water flowed into major fault zones at rates that at times reached 600 liters per second. By spring 2018, about 2.8 kilometers of tunnel remained unfinished.
Image related to tunnel construction at the Thượng Kon Tum hydropower project. Photo: Robbins.（VietVance）
In the fourth quarter of 2018, when the boring machine was about 250 meters from the connection point with a section being built by drill and blast, a collapse occurred in a fault zone ahead. An estimated 1,200 cubic meters of water and collapsed material entered the tunnel. The contractor used more than 22 tonnes of foam material to fill and reinforce the area, but the work encountered difficulties and the collapse continued to expand. The machine was then withdrawn, and the remaining roughly 250 meters was completed by drill and blast in the fourth quarter of 2019.
The project had a total investment of more than VND 9.4 trillion and an installed capacity of 220 MW. It connected to the national grid in 2021. In the first nine months of 2026, the project company recorded net revenue of VND 1.613 trillion, down 4% year on year, and after-tax profit of VND 628 billion, down 3%. Công ty TNHH Năng lượng REE holds 52.58% of the company’s charter capital.
Source: VietVance
