Anti-coal activists have locked themselves to heavy machinery to protest Adani's mega mine in central Queensland.

Three members of the Frontline Action on Coal group have used a sleeping dragon technique - which involves wrapping their arms around equipment then locking their hands inside metal pipes so they can't be removed by outsiders - to attach themselves to a grader, excavator and front-end loader near one of the workers' camps at Belyando.

Protesters have vowed to "do whatever it takes to peacefully stop" the $21.7 billion coal mine and rail project.

AAP