Ground Stability & Outrigger Setup Flashcards
7 cards from real CPO 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 Stability & Outrigger Setup flashcards as text
Ground that has been previously excavated and backfilled presents a unique hazard because:
Answer: Backfilled soil is rarely compacted to original density and has significantly lower bearing capacity than undisturbed ground
Backfilled soil, even when compacted, typically achieves only 85–95% of original soil density, resulting in lower bearing capacity and higher risk of settlement under heavy outrigger loads.
What is a 'void' in the context of ground assessment for pump setup, and why is it dangerous?
Answer: An underground hollow space such as an old utility tunnel, sinkhole, or deteriorated culvert that provides no load support
Underground voids provide zero bearing capacity; when an outrigger is positioned over one, the crib and float can suddenly collapse into it, causing immediate catastrophic tip-over of the machine.
When a concrete pump is set up on a public street or highway, what additional setup requirement is typically mandated?
Answer: Traffic control (cones, flaggers, signage) must be in place per local traffic control plans before setup begins
MUTCD (Manual on Uniform Traffic Control Devices) and local regulations require a traffic control plan with appropriate signage, barriers, and flaggers to protect workers and motorists before any equipment is set up in a roadway.
What information should a CPO operator record or verify from the pump manufacturer's load chart before finalizing outrigger pad sizing?
Answer: The maximum outrigger reaction force at each outrigger pad for the anticipated boom configuration
The manufacturer's load chart provides the maximum force that each outrigger transmits to the ground for various boom positions; this value is used with soil bearing capacity to calculate the minimum required crib area.
Why is it hazardous to set up outriggers directly over or adjacent to storm drain grates, manhole covers, or utility access covers?
Answer: Because these covers typically span hollow underground chambers not rated for heavy point loads and can collapse
Storm drains, manholes, and utility vaults are hollow underground structures; their covers are not designed to support the concentrated loads of pump outriggers and can fail, dropping the outrigger suddenly.
Which formula correctly expresses how to calculate the ground pressure under an outrigger pad?
Answer: Ground Pressure = Outrigger Reaction Force ÷ Outrigger Pad Contact Area
Ground pressure equals the outrigger reaction force (from the load chart) divided by the area of the crib pad in contact with the ground; this result must be less than the soil's bearing capacity.
What action should a CPO operator take if, during the pre-setup walk-around, they notice the ground at the setup location has been recently rained upon and appears saturated?
Answer: Substantially increase crib pad size, probe the ground for depth of saturation, and consult with the site supervisor before setting up
Saturated soil has dramatically reduced bearing capacity; the correct response is to increase crib size to compensate, assess how deep the saturation extends, and coordinate with site supervision — not to simply delay or proceed recklessly.