January/February 2023 - 83

Because the construction sequence
for the adjacent bui ldings was
uncertain at the initial phase of the
design, the Facility 610 system had to be
designed such that all structures could
be excavated at the same time, which
was extremely challenging due to the
complex interaction between the
adjacent excavations.
Monitoring and Performance
Criteria
Movement of the top of the slurry wall
was monitored on a weekly basis using
optical survey techniques.
The contract specifications set
threshold horizontal deflection limits of
the diaphragm wall at 0.5 in (12 mm)
with a maximum movement limit of
1.0 in (25 mm). The baseline measurements
were established prior to excavation,
and monitoring will be continued
until the structure is constructed
to grade.
At the time of preparation of this
paper, build-out of the basement was
underway and lateral deflections had
been limited to approximately 0.5 in
(12 mm) or less. The as-built deflection
numbers were comparable to estimates
made during the design process.
Mobilization and Site
Utilization
Logistics was a primary challenge for
the construction of this project due to
multiple concurrent activities to meet
the project schedule. In addition to the
diaphragm wall construction, the
foundation partner also installed 290
each 3 ft (0.9 m) and 4 ft (1.2 m) diameter
auger cast piles, 233 each 4 ft (1.2 m)
diameter cased drilled shafts and 526
each 1 ft (0.3 m) diameter tie down
anchors. For three shallower structure
excavations (up to 26 ft [8 m] in depth),
the foundation partner installed a
temporary CSM shoring wall that was
supported by one level of internal
bracing. More than 50 dewatering wells
were installed to manage and treat the
groundwater at the various excavations.
The site configuration, including
access/egress, installation sequence
and support equipment layout, was
carefully planned prior to mobilization.
Onsite daily meetings included all
d r i l l i ng s up e r i n t end en t s and
subcontractors to plan the next day's
activities, and a unique coordination
map was created each day to reflect the
new work areas . Thi s l eve l of
Primary panel concrete placement with simultaneous excavation in background
coordination was required to manage
the large site and ensure that spoils
were efficiently off hauled and readymix
concrete made on time deliveries to
drilling locations. At the peak, 80 trucks
of spoil were being loaded out while 80
trucks of concrete were being delivered
to the jobsite daily.
The equipment used to install the
diaphragm wall included a Bauer BC40
hydro cutter mounted on a Bauer MC96
crane, one hydraulic grab mounted on a
MC64 crane, one mechanical grab
mounted on Liebherr HS 885, one 300T
support crane, one 150T support crane,
a Bauer BE550 desander unit, a
centrifuge, and twenty-two 21,000 gal
(80,000 L) open top mixing tanks.
Diaphragm Wall Construction
Temporary reinforced concrete guide
walls were constructed along the
alignment of the diaphragm wall to
be utilized as a guide for the excavation
equipment and the setting of the
rebar cages.
Qual i ty cont rol of the panel
excavation is critical for the water
tightness of the diaphragm wall
system. Prior to concrete and rebar
placement, the panel excavation is
independently checked via a Koden
drilling monitor, which uses ultrasonic
waves to measure a precise profile of
the panel excavation to confirm it
meets dimensional tolerances.
Panel reinforcing cages were
assembled horizontally on the ground
at the project site and lofted to a vertical
position for installation. Bracing
embeds with shear studs and tieback
blockout pipe sleeves were all installed
in the rebar cage prior to lifting and
installation.
P l acemen t o f t he 5 , 000 ps i
(34,475,000 MPa) design strength
concrete was achieved via tailgate
placement into multiple gravity tremies.
In total approximately 25,000 cu yd
(19,000m3) of structural concrete were
placed for the slurry diaphragm wall.
DEEP FOUNDATIONS * JAN/FEB 2023 * 83
January/February 2023

Table of Contents for the Digital Edition of January/February 2023
