Tipping on an Unprotected Stockpile Edge
You are tipping a 25-tonne articulated dumper on a stockpile of excavated clay. The stockpile is about 4 m high, with a soft edge and no stop block or barrier. The excavator operator waves you back to within about 1 m of the edge, which is closer than the 3 m you normally keep. Recent rain has left 300 mm deep ruts, and you can see cracks in the ground parallel to the edge. There is no banksman in view. The wind is gusting to 25 mph, and dust is blowing across the pile. Your load is wet clay that may stick in the body. The site rule says tipping must be supervised where the edge is not protected. You have tipped here before in dry weather, but conditions have changed.
1. What checks and positioning decisions should you make before raising the body?
Read the worked answer
Stop before the edge and do not follow the excavator operator’s wave. The cracks parallel to the edge and the 300 mm ruts show the crest is unstable. Keep back to a firm, level area, ideally against a stop block, and use a banksman. Check for overhead lines and the wind effect on dust and stability. The 1 m position is too close for a 25-tonne machine on soft clay with an unprotected edge. If no safe tipping point or banksman is available, do not tip; ask the supervisor to establish one.
2. What is the correct discharge sequence, and what would you do if the load sticks?
Read the worked answer
Position squarely and level, apply the parking brake, select neutral, check behind and around, then raise the body smoothly. Discharge downwind if dust is an issue, but keep clear of the edge. Lower the body fully before moving. If the wet clay sticks, do not bang the body up and down, do not climb under a raised body and do not reverse with the body raised. Lower it and use the excavator or a safe cleaning method agreed with the supervisor.
3. The ground begins to crack and the machine leans. What now?
Read the worked answer
Lower the body immediately and keep it down. Do not raise it further to ‘empty quickly’. If the machine is stable enough, drive straight back away from the edge with gentle steering; sharp articulation could trigger a slip. If it is already leaning or the ground is moving, stop, apply the parking brake, radio for help and leave the machine only if it is safe to do so. Keep others away and report the unstable crest.