| Mid City Expo, Culver City,
CA
The project consists of:
5 each – 15’ Ø CIDH Pilings
6 each – 11’ Ø CIDH Pilings
12 each – 12’ Ø CIDH Pilings
15 each – 2’ Ø CIDH Pilings
15’ Ø CIDH PILING
Bents 2 through 6
The 15’ Ø Piles have drill depths of up to 112’ deep
and were constructed by stabilizing the surrounding
soil by means of a Cutter Soil Mix (CSM) operation.
The CSM panels were installed in an octagonal pattern
with the ends overlapping to form a compression ring.
The panels were 9’ – 2” long by 39” wide and extended
to depths of 118’ below ground surface.
The CIDH reinforcing steel cages were 14’ 6” Ø
by 100’
long and weighing 170,000#. Malcolm Drilling designed
and built a Tipping Frame that allowed a single Sumitomo
1500 (150 ton) Crane to lift the cage from horizontal
on the ground to complete vertical without damage or
racking of the cage. The cage was then released from
the Tipping Frame and lifted and placed into final location
within the drilled shaft by the Kobelco 250 (250 ton)
Crane. Entire operation from initial lift by the Sumitomo
to the placement within the shaft lasted 90 minutes.
MDCI used the option to complete the CIDH Piles in
two separate concrete pours at Bent 4 only. The first
pour was completed from the pile tip elevation up to
a construction joint (71’ with 480 c/y of concrete).
The construction joint is 29’ below the top of the CIDH
cut-off elevation. The second pour was completed following
the installation of the column cage from the construction
joint elevation to the pile cut-off elevation (29’ with
200 c/y of concrete).
Bents 2, 3, 5 and 6 were completed with one continuous
concrete pour. The CIDH portion was poured to below
the column elevation (-29 feet below cut-off elevation),
the column cage was then placed and secured into the
shaft and the concrete placement to cut-off elevation
was complete. (Total concrete placed on these days was
680 c/y). The column cage extended 27’ into the CIDH
pile and extended 23’ above cut-off elevation. All concrete
was placed using MDCI’s 36M boom pump.
The completion of these 15’ Ø
shafts presented numerous
challenges for MDCI. Among the toughest were the lack
of adequate setup room at each drill location site,
working adjacent to live traffic, the size and weight
of the reinforcing steel cages, subsurface conditions
consisting of a high water table elevation, and sand
and gravel zones, and the Contract Specifications for
Mass Concrete. MDCI eliminated the risk of the caving
ground conditions and ultimately eliminated the Mass
Concrete restrictions by constructing soil stabilizing
panels around the perimeter of the drilled shaft. The
Cutter Soil Mix (CSM) panels allowed the shaft to be
drilled in the dry to tip elevation and provided a cement
liner of the side walls. The Mass Concrete plan provided
by MDCI included the use of Thermal Sensors and Cooling
Tubes within the concrete attached to the reinforcing
steel cage to monitor and control the heat produced
in the center of the shaft during hydration of the concrete.
The concrete (CSM) panels increased the surface temperature
of the shaft walls to 100° F and allowed the placement
of a lower cement volume concrete (6.8 sack with 40%
fly ash at a slump of 5”). Had the shaft been completed
by means of slurry (polymer) displacement, the surface
temperature of the shaft walls would have been much
lower, between 60° F to 65° F, and the concrete would
have had a higher sack content (8.6 sack with 40% fly
ash at a slump of 9”). The lower surface temperature
and higher cement content would have exceeded the allowable
maximum and differential temperature per the specifications
resulting in a rejected pile.
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