Ground Bearing Pressure and Outrigger Setup Flashcards
7 cards from real NCCCO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Ground Bearing Pressure and Outrigger Setup flashcards as text
Which soil condition would have the LOWEST allowable ground bearing capacity?
Answer: Soft wet clay
Soft wet clay has very low shear strength and allowable bearing capacity, often less than 1,000 psf compared to thousands of psf for compacted granular soils.
What is the function of a load cell or outrigger force indicator when used during crane operations?
Answer: It provides real-time measurement of the actual load on each outrigger
Load cells at outrigger pads measure actual outrigger reaction forces, allowing comparison against the soil's allowable bearing capacity.
A crane is operating near an excavation. How does the proximity to the excavation affect outrigger placement?
Answer: Outriggers placed too close to an excavation edge can cause slope failure or cave-in
Concentrated outrigger loads near an excavation slope can exceed the soil's shear strength and trigger a slope failure or wall collapse.
Which document would provide the best engineering data on allowable ground bearing pressure for a specific crane setup on a construction site?
Answer: A geotechnical or soil investigation report for the site
A site-specific geotechnical report provides measured soil bearing capacity data from borings or tests, giving the most accurate and reliable values.
What effect does increasing the size of an outrigger float pad have on ground bearing pressure?
Answer: It decreases ground bearing pressure by spreading the load over more area
A larger pad area distributes the same outrigger force over more square footage, reducing the pounds per square foot of pressure applied to the soil.
During a lift, an operator notices one outrigger float has settled noticeably more than the others. What is the correct action?
Answer: Lower the load, re-inspect and re-level the crane before resuming
Differential settlement indicates inadequate ground support or cribbing failure; the load must be set down and the setup reassessed before operations continue.
An outrigger pad rated for 50,000 lbs is placed on soil with an allowable bearing capacity of 2,000 psf. What minimum pad area is required to stay within the soil's capacity?
Answer: 25 square feet
50,000 lbs ÷ 2,000 psf = 25 square feet minimum pad area needed to keep ground bearing pressure at or below the soil's allowable capacity.