The Adani group had applied for the Northern Australia Infrastructure Facility loan for building the 388-km rail line to connect the Carmichael coal mine to the sea port.
Adani Enterprises recently also inked a pact to buy out Linc Energy's royalty rights from the Carmichael coal project for AUD155 million.
Adani's plan to build one of the world's biggest coal mines has been hampered time and again.
Australia's green political party on Wednesday warned the government for approving India's Adani group's plan to expand a major coal port on the fragile Great Barrier Reef coast, saying it will hasten the death of the natural wonder, a World Heritage site.
"I am proud to announce the project has Final Investment Decision (FID) approval which marks the official start of one of the largest single Infrastructure -- and job creating -- developments in Australia's recent history," Gautam Adani said.
Reports said that Adani took legal action to override the W&J people.
Sources said Adani had not been able to tie up any financing for the coal project
Adani will go ahead with its $15 bn mine, rail and port project.
Was Adani able to clinch this loan merely as a result of his proximity to Prime Minister Narendra Modi?
Adani's $15-billion Carmichael coal mine is stuck since 2010.
Acquisition of stressed infrastructure assets has pushed its debt to over Rs 1 lakh crore, highlighting concerns about its growth strategy.