Broken struts are a common occurrence in the Motherlode Mine. When both waterwheel struts break, no more Pay dirt can be processed until they are repaired.
The broken struts can be repaired by clicking on them, as long as you have a hammer in your inventory. Doing so grants 1.5 times the Player's current Smithing level in Smithing experience.
If the player constantly hops worlds to repair struts, they can gain anywhere from 18k-30k Smithing experience/hr. This can be useful for Ironman players.