November/December 2021 - 18

piles were clay, alluvium, boulders
and cobbles, glacial till and bedrock.
To accommodate excavation of the
southeast area of the stadium for
field-level structures, the work
started there and progressed
clockwise. Installation of the 653
primary and secondary piles was
completed over five months while
running two shifts at five days a
week. To drill at the sizes and depths
needed and tackle cobbles and
boulders, the subcontractor used its
largest rigs: Bauer BG40 and BG45
drilling rigs. The approach helped
maintain the fast-track schedule
and cost effectiveness.
The 46.5 in (1,180 mm) diameter
collaborated with Osborn and TSJV to
explore other deep foundation
options, such as driven piles.
Selecting large diameter ACPs was
found to save time and money.
In December 2019, a month after
the secant pile wall construction
began, Goettle was awarded the
contract to drill large diameter ACPs
for the stadium's foundation. To carry
out the scope of work, a third drill rig
- a Bauer BG28 - was added to
accompany the larger rigs. It was
used to drill a total of 506 piles,
ranging in depth from 50 ft to 75 ft
(15.2 mm to 22.8 m), with diameters
of 24, 36 or 48 in (61, 91 or 122 cm).
A string of 80 ft (24.38 m) CFAs
primary piles were installed using
continuous flight auger (CFA) drilling
methods with the Bauer BG45 and
averaged 80 ft (24.38 m) in depth. The
secondary piles were installed using sectional casing with the
Bauer BG40. Although the rig for the primary piles had
software to record information for quality control reports
(including pile depths and volume of auger cast grout placed),
secondary pile reports were recorded by hand in the field. The
total grout poured in this phase was 27,000 cu yd (20,643 cu m).
Stadium Foundation Construction
The stadium foundation system, designed by Osborn
Engineering, consists of reinforced concrete pile caps
supported by auger cast piles (ACPs), which are quite often
used for stadiums. In its design assist role, Goettle
Completed stadium foundation piles at field level
Sectional casing installation in secant wall secondary pile
was used, with drilling taking four
months. Drilling conditions were the
same for the ACPs as for the secant
piles: clay, alluvium, boulders and
cobbles, glacial till, and finally, bedrock. Due to numerous
other subcontractors on the job site by then, space was
limited, and it became challenging to shoehorn the huge
machines into many tight spaces to drill and pour.
Foundation pile installation wrapped on time in June
2020, despite the added impact of contending with COVID-19
protocols and effects on the supply chain. Precautions such as
masking, hand washing and sanitizing stations were
introduced all over the site, as well as disinfecting surfaces,
and following safety team updates on the latest infectious
disease control protocols. Work continued without
interruption and with no positive tests or lost time.
Pitch Access Tunnel
The final, most challenging phase of
construction was the pitch access
tunnel for vehicle access to and from
the field, and the tunnel entrance's
retaining walls. The base slab is 6 in
(15.2 cm) reinforced concrete to
accommodate vehicular loading. The
walls provide separation from the
seating bowl at pitch level, and double
as retaining walls for the elevation
change from the playing field bowl to
the tunnel base. As the tunnel passes
under the main concourse level, the
slab above it is supported by the
retaining walls below.
18 * DEEP FOUNDATIONS * NOV/DEC 2021
November/December 2021

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