A plan to cancel weekday trains on the Grange line in Adelaide has been modified, and shuttle trains will now run to and from Woodville.

The daytime weekday services will be affected by platform closures at Adelaide Railway Station during work above the station to expand the city's Convention Centre.

A shuttle train between Grange and Woodville will operate in conjunction with buses, possibly for a year from February 27.

The Tonsley rail line in Adelaide's south is also to face disruption because of the city work, but South Australian Transport Services Minister Chloe Fox says a shuttle cannot be operated on the Tonsley line.

"The Tonsley line has a different engineering issue in that there is nowhere for that train to turn around," she said.

"There's no depot, so while we can do it on the Grange line we physically can't do it on the Tonsley line."