The rapid removal of three level crossings during a round-the-clock construction blitz in Melbourne's south-east has led to serious injuries of workers on the site.

The John Holland Group is removing level crossings in Bentleigh, McKinnon and Ormond, as part of a half-billion-dollar project also involving removal of a fourth set of boom gates in Glen Iris.

To complete the three Frankston line level crossing removals, the railway has been shut for 37 days, and will open again next Monday, August 1.

Trains are being substituted with buses while an estimated 250,000 cubic metres of soil is removed from the railway line and new infrastructure is built.