Operator of the Komatsu WA500 Front End Loader parked the FEL parallel to the Loadout face of the stockpile. The Operator dismounted the FEL to go to the restroom inside the pivot area of the FEL. As the operator unfastened their bib overalls, the stockpile sloughed hitting the miner in the back of the legs, knocking them down to their knees, pinning the against the FEL.