Work has begun to repair a 40m stretch of railway near Ockley station that was damaged by a landslip on Christmas Eve.
The stretch of embankment collapsed following ‘intense and prolonged rain’, Network Rail said, pitching more than 1,000 tonnes of spoil down a slope.
Network Rail added engineers are on the site and are ‘doing all they can do’ to mend the stretch of railway.
Tim Robinson, route managing director at Network Rail, said: “It has been a considerable challenge just to get to this stage, as we’ve had to build a new road to bring our plant to the site of the slip.
“Now we are underway things are going well, and we’ve begun to install a wall of sheet piles. These are partly buried in the ground, to form a new base to the embankment.
“We will then need to deliver between four and five thousand tonnes of new material to fill the gap before we can begin to run trains again.”
The site of the landslip is not accessible by road, making it difficult for Network Rail to send their machinery to the scene.
Services have been disrupted across the county due to storm damage through December and January.
Mr Robinson added: “This has been a difficult time for passengers on this line and we appreciate their patience.
“The weather over Christmas really was unprecedented and we are gradually getting the railway back to where we want it.”
A limited service of peak-hour trains has been operated by Southern Rail over the undamaged line furthest from the slip.
Network Rail hopes to return the line to full service between early February and the middle of the month.
After that, the former footpath will be returned to its previous location and the area will be replanted.