March/April 2023 - 84

range from 18 in (45mm) up to 10 ft (3 m)
depending on the anticipated equipment,
loading conditions and soil
properties. While working pads are
typically a temporary element of the
construction workplan, with proper
designing and construction phasing they
can be successfully incorporated and
used as a permanent element of the
design. The gross weight ground
pressure of the equipment alone should
never be used to design the working pad.
The solution lies in a much more
complex analysis of the operating
maneuvers under differing loads.
Quicklime and cement are the two
most common reagents used for
working load transfer pads. Some soils
work best with a blended combination
of the two reagents. The choice depends
completely on the soil. Quicklime is
permanent foundation systems. High
moisture contents and variable soil
conditions including 1906 earthquake
debris layers intermixed with bay mud
created challenging conditions for this
high-profile project.
U.S. Government Veterans Administration
Hospital, Yountville, CA
Emergency stabi l izat ion was
required on this project. The steel crane
mats started to yield during crane
positioning. Three weeks of heavy rains
compromised the crane pad area. A 24
in (610 mm) thick cement stabilized pad
was constructed along with three other
pads in the building footprint area. A
total area of 20,000 sq ft (1,860 m2) was
treated in one day with minimal
schedule impacts.
generally used on lean to highly plastic
clays, while cement is appropriate for
gravelly, sandy and silty materials.
Intermediate soils (i.e., soils containing
sand, clay and silt) may require a
combination of quicklime and cement.
Laboratory testing will determine the
appropriate reagent type. The percentage
used is based on the dry soil weight
of the soil being treated. Test specimens
are prepared per ASTM D1633 for
cement and ASTM D5102 for lime.
The compaction effort used for the
specimens follows ASTM D1557
procedures. This compaction effort
better matches the actual field
compaction and equipment used.
Overall the goal is to build it first in the
lab and then replicate the recipe in the
field. These testing guidelines are well
documented from established agencies
including Portland Cement Association,
Public Works Standards, Inc.'s
Greenbook, American Association of
State Highway and Transportation
Officials, Asphalt Recycling & Reclaiming
Association and many state Departments
of Transportation.
Construction
Once the design is complete and
approved, the construction of the
working pad or load transfer pad can
begin. The process includes three main
pieces of equipment, the spreader, the
reclaimer (mixer) and the compactor.
Supporting equipment includes water
trucks, which are hooked up to the
mixer and supply water necessary for
hydration and compaction. In saturated
soil conditions water trucks typically
are not needed because the in-situ
Warriors Arena mixer crew
Warriors Arena pad area
84 * DEEP FOUNDATIONS * MAR/APR 2023
March/April 2023

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