The US$5.5 billion project will extend the life of the 100-year-old mine for many decades and see it produce 140,000 tonnes of copper a year following a seven-year transition from open-pit operations.
"Chuquicamata is not just another project; it is unique. Its complexity and magnitude have no equal in the Chilean market; there has never been a project with this scope," said VP projects Gerhard Von Borries.
Having taken 15 years since the first engineering works were completed, Chuqui underground has seen the development of three levels underneath the open pit to a depth of 989m below the pit floor, with some 142km of tunnels built.
The pit is some 5km long and 3km wide, and produced 320,744t of copper in 2018.