Laos tunnel completed following severe deformations

27 July 2020

Excavation has been completed on the 7km Houay Phoulai Tunnel in northern Laos following a difficult bore which saw daily deformations of supporting steelwork in excess of 100mm.

Some 400km north of the capital Vientiane, the tunnel was mined through difficult geological conditions which made its construction ‘highly risky’, according to China’s Xinhua news agency.

Located in the Luang Prabang geological suture zone, the tunnel crosses multiple large faults and geological fracture zones, in overburdens of up to 645m. In addition to the severe soft-rock deformations, the excavation encountered unfavourable geology in the form of karst, rockbursts, water inrushes and mudflows. The severe deformations of the initial supporting steel framework experienced in soft rock resulted in badly twisted and deformed steelwork which crews overcame with enhanced support.

Throughout the construction process, China Railway No. 8 Engineering Group (CREC-8) undertook real-time monitoring of gas and other toxic and harmful gases, allied with various geological forecasting methods to ensure the safety of tunnel crews.

Forming a part of China’s strategic Belt and Road Initiative, the China-Laos Railway will also help Laos become less landlocked and more a land-linked hub. With 75 tunnels totalling 198km in length, the 422km railway extends from Vientiane northwards to the Boten gate on the Chinese border. The project is expected to be completed in December 2021.