When blocking is needed under outriggers, what determines the size of the block?

When blocking is needed under outriggers, what determines the size of the block?

• A. Ground bearing pressure generated by crane
• B. Crane weight
• C. Operator experience
• D. Weather conditions

Answer: (A)

Blocking under outriggers is about keeping the ground reaction within what the soil can safely bear. The size of the block is chosen so the pressure on the ground under each outrigger does not exceed the soil’s allowable bearing capacity. In practice, you determine the needed block area by dividing the load borne by the outrigger by the ground’s allowable bearing pressure. So heavier loading or weaker ground means you need larger blocks; stronger ground or a wider outrigger spread reduces the required size. Weather can affect soil strength and may push you to use larger mats, but the determining factor for block size is the ground bearing pressure generated by the crane. Example: if each outrigger carries 20,000 lb and the soil can safely bear 2,000 psf, you’d need about 10 ft² of block area per outrigger.

Blocking under outriggers is about keeping the ground reaction within what the soil can safely bear. The size of the block is chosen so the pressure on the ground under each outrigger does not exceed the soil’s allowable bearing capacity. In practice, you determine the needed block area by dividing the load borne by the outrigger by the ground’s allowable bearing pressure. So heavier loading or weaker ground means you need larger blocks; stronger ground or a wider outrigger spread reduces the required size. Weather can affect soil strength and may push you to use larger mats, but the determining factor for block size is the ground bearing pressure generated by the crane.

Example: if each outrigger carries 20,000 lb and the soil can safely bear 2,000 psf, you’d need about 10 ft² of block area per outrigger.