September/October 2021 - 112

foundation for five water storage tanks.
These drilled, full displacement, cast-inplace
concrete rigid inclusions were
installed by powerful, fixed-mast drill
rigs capable of applying high rotational
torque and crowd forces to the unique
tool. Installation with this system was
performed in a safe, simple and rapid
single-pass process that densified the
soil, improved shaft friction and increased
overall pile capacity. Use of DDP
RI also eliminated the removal of spoils.
As the innovative DDP tool advanced
Reinforcement cage positioning into concrete CFA pile
The CFA tool was removed without
rotation to minimize disturbance to the
upper, soft soils. Hydraulic auger
cleaners were used to remove soil
cuttings from the auger and eliminate
the possibility of spoils falling and
injuring workers on the ground. Fulllength
steel cages were installed in
these piles with a service crane.
DDP Construction: SBM was granted
a license to install Morris-Shea's
patented DeWaal Drilled Displacement
Pile System at the PEMEX Dos Bocas
Refinery Predio 1 jobsite as the deep
Steps of DeWaal Drilled Displacement Pile System
into the ground, the partial-displacement
auger transported soil to the fulldisplacement
element. This action
thrusted 100% of the cuttings laterally
against the side walls of the borehole,
causing densification of the soil profile. A
centralizer at the bottom of the drill mast
maintained horizontal control of the
tooling. The heavy wall drill stem served
as a temporary casing that followed the
tool and stabilized the borehole.
Prior to lifting the tool, the drill stem
was filled with a self-consolidating, high
slump, coarse aggregate concrete. It
functioned as a tremie pipe from which
pressurized concrete flowed while the
DDP tool ing was wi thdrawn. A
sacrificial endplate was left behind in
direct contact with the soil. The reverse
flight located on the top side of the
displacement element assisted with the
extraction by cutting and recompacting
any loose soils. This added soil
densification helped to minimize
concrete overc
o n s ump t i on .
Drill tenders finished
by inserting
a prefabricated
reinforcing steel
cage into the concrete
pile. Overall,
the DDP system
was ideal for installation
as rigid
inclusions in the
liquefiable soils
found at the south
end of the Predio 1
jobsite.
112 * DEEP FOUNDATIONS * SEPT/OCT 2021
Conclusion
The PEMEX Dos Bocas Refinery deep
foundation projects, Predio 1 and Predio
2, presented unique concerns regarding
liquefiable soils, irregular jobsite
availability and site size.
Mitigating liquefaction at the five
water tank sites required that Shea
Brothers Mexico develop a designbuild
solution that addressed the
problem created by loose sands in the
south area of Predio 1. SBM worked
with geotechnical engineers to design
rigid inclusions, based on the DeWaal
Drilled Displacement Pile System, that
mitigated liquefaction inside each
water tank's footprint.
SBM utilized production efficiencies
at both Predio 1 and 2 that were
developed over decades by its and
MSB's experienced geotechnical professionals.
These efficiencies were
employed at the Predio 2 project site,
yet SBM crews were often required to
create workarounds as a result of the
delays of other contractors on site.
Consequently, SBM teams shifted drill
rigs to and from distant drill sites as
they became available.
SBM developed new site-specific
soil solutions for the unique concerns
of the Predio 1 and Predio 2 projects
and successfully drilled more than
9,000 RI and piles at the PEMEX Dos
Bocas Refinery.
Gordon King is an engineer manager with
Morris-Shea. He received a bachelor's degree
from the University of Dundee, Scotland, and a
master's in geotechnical engineering from the
University of Durham, England. King has more
than 30 years of geotechnical consulting and
specialist foundation contracting experience, and
is currently a member of the DFI Augered Castin-Place
and Drilled Displacement Pile
Committee.
September/October 2021

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