A grain bridge forms when grain in poor condition exists throughout a bin. Cavities or pockets of loose grain can form under the crusted level when the auger begins to unload grain from the bin. Grain bridges are not stable, and if you are standing on top of a grain bridge when it collapses, you can quickly become entrapped in the grain. Once you fall through the grain bridge and are trapped, it may be difficult to locate you because the grain will flow rapidly into the area around you.
The proper way to break up or remove a grain bridge is to use a long pole inserted through an access hole from outside the grain bin.