Network Rail engineers stabilised a slope on the south side of Harbury near Leamington part of a £9 million investment.
The major improvements started in December 2019 and workers left the site on March 5.
From start to finish the major earth moving project work took 15 months to carry out.
The underground conditions in the area have caused problems for the railway ever since it was built in 1852*.
Most recently in 2015, 300,000 tonnes of earth moved on the north side of Harbury tunnel forcing the important passenger and freight railway route between the Midlands and London to close for six weeks.
Emma Gray, scheme project manager at Network Rail, said: “This significant investment to secure this part of the Chiltern main line will ensure reliable journeys for passengers between Birmingham and London for many decades to come.
“The ground here, made up of layers of limestone and shale, can be unstable and could potentially cause issues for the railway running through it. This preventative work will stop future slips and make it much more secure.
“We know Harbury very well after the huge landslip in 2015 and I want to thank the local community for their patience while we carried out this important work to protect the railway.”
Large nails and piles have been dug into the slopes beside the tracks to make them stronger.
A new retaining wall has also been built at the bottom of the railway cutting to prevent soil movement.
The project has been carried out during the daytime while passenger and freight trains continued to run below, meaning no disruption to services and no noisy overnight work.
Eleni Jordan, commercial & customer strategy director for Chiltern Railways, said: “The work that Network Rail have carried out at Harbury will ensure that we can continue to run reliable and punctual services for our customers for many years to come.”
For more information on how Network Rail carries out this type of work visit www.networkrail.co.uk/earthworks-cutting-slopes-and-embankments.