Only the alliance captain and vice-captains can build the alliance mines after completing at least one alliance fort, and you can only build two Alliance Super Mines at the same time within the alliance territory.

To build a mine, you must follow these steps:
-Click on the “Alliance” icon in the bottom right corner of the screen.
-Choose (Alliance Territory)
-Click on (Alliance Mines).
-Choose the mine that you want to build, check the requirements to build it, and then start the building process