It's certainly possible to carve a mile-long tunnel through rock with fire, but it will take you more than 15 years to do it!
Thousands of years ago, ancient Romans built tunnels by heating rocks with a fierce fire, then cooling them with a splash of cold water. The temperature change caused rocks to split and break off in chunks. This technique was called fire-setting.
Thousands of fire setters died in mountain tunnels from the toxic fumes and scorching heat, so you might want to consider another technique!