March/April 2022 - 78

A modulus load test program was
performed on the GCCs to confirm the
design assumptions. Sacrificial test
piers and uplift reactions were installed,
allowed to cure for at least 14
days, and then tested at up to 200% of
the design load. The GCC test pier was
installed to a depth of about 65 ft
(19.8 m) to penetrate the marine deposits.
During the test, the GCC exhibited
acceptable stiffness and creep
behavior to up to 200% of the design
load, with a deflection of 0.52 in
(13.2 mm) at the pier design stress of
140 ksf (6.72 MPa). Comparison with
the DIP deflection of 0.69 in (17.5 mm)
indicated the GCC and DIP systems
would be compatible at the design
loads.
Sonic drilling and ductile iron pile installation
The test pile deflected 0.69 in
(17.5 mm) at the design load of 85 tons
(756 kN), and 1.50 in (38.1 mm) at the
200% load. The pile rebounded almost
entirely, with a net downward movement
of 0.14 in (3.6 mm) after the full
load test cycle was complete. The load
test results showed the pile successfully
supported the full test load, and that
more than 150% of the design load
reached the bearing layer.
Based on the successful load testing
program, a total of 61 pile locations were
designed for the area characterized with
the debris fill. During production
installation, as the sonic drilling advanced
through the debris, two modular
16.4 ft (5 m) DIP sections were immediately
installed within the predrilled,
cased hole. The first two sections
were rapidly installed, followed by
backfilling of the annular space within
the cased hole. The sonic tooling was
then removed to be used at the next hole
location. At the conclusion of all sonic
drilling, Helical moved back to each pile
location, rapidly advancing the DIPs to
their final depths, which ranged between
65 and 70 ft (19.8 and 21.3 m). The
self-coupling bell and spigot ends of the
DIPs made it easy to start and stop the
system installation. The completion of
78 * DEEP FOUNDATIONS * MAR/APR 2022
the pre-drilling and setting of initial
DIPs took about 3 weeks, while the
ductile iron pile installation to final
depth was completed in 5 days.
Ground Improvement Steps
Based on the structural loads and geotechnical
conditions, Geopier Foundation
Company recommended using 16 in
(0.41 m) diameter GCC for support of the
foundations. To support the slab-ongrade,
20 in (0.51 m) diameter rammed
aggregate piers were used. Foundations
were designed to limit settlement to 1.5
in (38 mm) or less and to be compatible
with the deflections of the DIPsupported
foundations (i.e., that they
would not result in excessive differential
settlements as a result of differences in
elements' stiffnesses).
In addition to the modulus load tests,
several QC systems were implemented
during production, including concrete
slump testing, concrete cylinder collection
and breaking, GCC mandrel
calibration, concrete pump calibration,
bottom-stabilization tests, crowdstabilization
tests, and monitoring of
concrete pumping pressures. For each
element's construction, Helical electronically
logged the installation
process, including installation length,
concrete volume, driving resistance and
pump pressures. Haley & Aldrich also
provided a full-time representative to
confirm installation was in accordance
with the design submittal.
An ABI MOBILRAM TM 18/22 was
mobilized for installation of the ground
improvement system, taking about 5
Sonic drilling core of buried foundation wall
March/April 2022

Table of Contents for the Digital Edition of March/April 2022
