The main part of Queen Street station in Glasgow will be shut in 2016 while worn concrete slabs in its tunnel are replaced.
Network Rail said the work could not be done safely while trains were running.
It plans to divert as many services as possible to Queen Street low-level station and Glasgow Central.
Project director Rodger Querns said: “The tunnel will close for three to four months. The work will undoubtedly be disruptive and we are looking at options to divert traffic.”
The news came as the rail firm unveiled plans for the £104 million expansion of Queen Street for longer and faster trains on the main line to Edinburgh.
Network Rail launched a public consultation yesterday so it could seek powers to demolish two adjoining buildings to make way for the scheme by compulsorily purchasing them.
The project, to start in April 2015 and be completed by 2019, is part of the £742m Edinburgh Glasgow Improvement Programme (Egip) to electrify the line. It will also enable the station to handle an anticipated 40 per cent increase in passengers from 20 million to 28 million by 2030.
The tunnel work is not part of Egip, but will coincide with it.
Passengers on the line are already facing disruption, with the Winchburgh tunnel in West Lothian due to close for six weeks for Egip work, with no date set.
The station overhaul includes a new glass frontage on to George Square, longer platforms and an enlarged concourse with twin-level cafes and shops on the current east-side car park.
There will also be links with an extension of the Buchanan Galleries shopping centre, which is due to start being built in October.
The new facade will require the removal of part of the Millennium Hotel, which has shrouded the station since the late 1960s, and the neighbouring Consort House office block, which is headquarters of Strathclyde Partnership for Transport.
Labour transport spokesman Mark Griffin said: “The failure to publicise the planned closure is worrying. These works are necessary repairs and, as a service user myself, I would expect clarity on why this has to happen, what services will be affected and how it will alter people’s journeys.”
Independent watchdog Passenger Focus said the redevelopment was “absolutely necessary”, but called for ticket discounts during the disruption. Manager Robert Samson said: “Most passengers will benefit in the long-term from the improved station. However, passengers won’t be happy about the disruption this project will cause.
“The rail industry will need to work hard to give passengers plenty of notice of changes to timetables and be on hand to provide them with the necessary help and information.
“The industry should also consider offering discounted tickets and compensation for passenger inconvenienced by this engineering work.”
Transport minister Keith Brown said: “Egip has already delivered the stunning new-look £25m Haymarket station in Edinburgh, and this complete transformation of Queen Street means passengers will benefit at both ends and at all points in between.”
A Network Rail spokesman said: “Significant portions of the slab track within Queen Street tunnel have deteriorated and require replacement. This is not unexpected and it was included in our track renewals budget for the 2014-2019 period.
“We anticipate that this work will happen during 2016 and, to deliver it as safely and efficiently as possible, we will need to close the tunnel for around three to four months. We are still assessing how best to deliver this work and also considering options for services including diverting trains to the low level station and to other locations, such as Glasgow Central.
“Every effort will be made to deliver the renewal as quickly as possible and to keep disruption to passengers to a minimum. We will also assess if the track renewal work and station redevelopment can be aligned to further reduce disruption for passengers and potentially create efficiencies for the projects.”