The Thames Tunnel, a nearly two-mile railway line that will help connect Reading in Berkshire to Shenfield in Essex as part of the Crossrail project, will be unveiled by the Chancellor today.
Part of the £14.8 billion Crossrail project, it is expected to cut journey times and boost rail capacity in London.
George Osborne said the project will provide a major boost the economy.
"As part of our long term economic plan we are investing in infrastructure around the country to create a more balanced, resilient economy," he said.
"Crossrail is not only providing extra speed and capacity for London's passengers, but also supporting new housing, jobs and businesses."
The project is expected to generate 75,000 business opportunities and support the equivalent of 55,000 full time jobs across the UK, according to the Government.