Breakout Session: Understanding Ground Bearing Capacities Ground stability is one of the most important factors to be considered with crane set up. This session will review the underlying physics and reaction forces, as well as group pressures. Learn best practices in ground stabilization methods and techniques including crane pads and mats; cribbing and shoring; crawler crane pads and more. Speakers: Jeff Steiner, Owner, Bigfoot Construction Equipment Mike Walsh, President, Dearborn Companies

1. STRENGTH STABILITY
SAFETY
JEFF STEINER
Owner, Bigfoot Construction Equipment

2. STRENGTH, STABILITY & SAFETY
• STRENGTH
The capacity of an object or substance to
withstand great force or pressure
• STABILITY
The state of being stable, firmly fixed, not to
give way or overturn
• SAFETY
The condition of being protected from
danger, risk or injury.

3. ABOUT ME
• U.S. Veteran – Army 82nd Airborne
• Journeyman Lineman (18 years)
• Certified Crane Operator (OSHA 20)
• Built, tested and designed outrigger pads
for Bigfoot since 1991

4. GROUND BEARING CAPACITY (GBC)
In geotechnical engineering, bearing
capacity is the capacity of the soil to
support the loads applied to the ground.
The bearing capacity of soil is the
maximum average contact pressure
between the foundation and the soil which
should not produce shear failure in the soil.

5. 4 SOIL CONDITIONS
1. SOLID ROCK
2. GRADE A SOIL CONDITION is cohesive and has a high unconfined
compressive strength; 1.5 tons per square foot or greater. Examples:
sandy clay, and clay loam. Soil can not be classified as type A if it is
been previously disturbed, if it has water seeping through it, or if it is
vibration from sources such as heavy traffic or pile drivers.
3. GRADE B SOIL CONDITION is cohesive and has often been cracked or
disturbed, with pieces that don't stick together as well as Type A soil.
medium unconfined compressive strength; between 0.5 and 1.5 tons
foot. Examples: angular gravel, silt, silt loam, and soils that are
sources of vibration, but could otherwise be Type A.
4. GRADE C SOIL CONDITION is the least stable type of soil. Type C
includes granular soils in which particles don't stick together and
a low unconfined compressive strength; 0.5 tons per square foot or
gravel and sand. Because it is not stable, soil with water seeping
automatically classified a Type C soil, regardless of its other

6. POINT LOADING
• A base of an outrigger measures 12” X 12”
• It’s holding 30,000 pounds
• The weight per square inch would be:
30,000 LBS / 144 sq. inches of base =
208.3 PSI

7. DISPLACING PSI
• Add a 36” X 36” outrigger pad
• The BIG FOOTPRINT will now be 1,296 sq. inches
• Now the weight per square inch would be:
30,000 LBS / 1,296 sq. inches of base =
23.1 PSI

8. OUTRIGGERS PADS DISPLACE LOAD
• Make A BIG FOOTPRINT
• Transfer PSI or load from
outrigger to outrigger
pad to the ground

9. STACKING, CRIBBING & DUNNAGE
• The bottom layer will always
carry the load or displace PSI
to the ground
• The top layer is the cushion.
This broadcasts the PSI
through the cribbing and base
outrigger pad
THE RIGHT WAY

10. NOT THIS…
• Point loading at the base—which is
carrying the load
• Gaps in cribbing
• Improper height compared to base

11. OSHA 1926.1402
OSHA 1926.1402 states: Cranes must be assembled on ground that is firm,
drained and graded sufficiently, in conjunction with supporting materials, such as
blocking, cribbing, pads or mats, to provide adequate support and levelness.

12. ASME B30.5-3.2.1.5(i)
FOR THOSE NOT IN CONSTRUCTION
• Blocking under outrigger floats, when required, shall meet the following requirements:
• SUFFICIENT STRENGTH to prevent crushing, bending, or shear failure.
• Such thickness, width and length, as to completely support the float, transmit the load to the
supporting surface, and prevent shifting, toppling, or excessive settlement under load.

13. SETTING UP LEVEL
• Follow manufacturer’s
instructions on crane set up
• Must be within 1% of
tolerance/grade

14. GRAVITY ONLY WORKS ONE WAY
• 50% crane failure, including
collapse, is from improper use
of outriggers & outrigger pads.
• Proactive safety approach
should be using outrigger pads
on any and every set up

15. USING THE RIGHT MATERIALS
• USE MATERIALS WITHOUT BRITTLE FAILURE