May/June 2021 - 17

filled steel pipe piles) at Pier One. The goal was to support the
new apartment buildings and parking garages to save
Massport significant project costs. CDM Smith and McLaren
teamed to develop an innovative pier retrofit and pile load
testing program to meet this goal. The purpose of the load
testing program was to determine if the existing piles could
support design loads of 240 kips (1,068 kN) for project financial
feasibility, and of up to 300 kips (1,334 kN) to significantly
reduce future foundation costs.
value of the supporting soil, or by performing load testing or
redriving on representative foundation elements.
Because of limited information regarding initial design
and installation of the piles, the geotechnical engineer
determined that a detailed pile load test program was required
for the project. The pile load testing program on representative
foundation elements would determine whether the existing
piles could be reused to support the new structures.
Prior to the pile load testing, the structural engineer
developed a pile repair plan to address
corrosion issues within the splash zone
and mean-low-water zones where
corrosion had reduced the steel thickness
to less than 1/8 in (3 mm) from the original
1/2 in (13 mm). The underwater repair
utilizing licensed divers consisted of
grouting an 18 in (46 cm) diameter, 0.5 in
(13 mm) thick steel pipe (sleeve) over the
existing piles and the annulus. The steel
sleeve repair plan permitted a structural
transfer of up to 300 kips (1,334 kN) per
pile to the foundation-bearing strata.
Subsurface profile across the Pier One footprint
Pile Load Testing
Financial feasibility of the project
depended greatly upon the results of this load testing
program. Therefore, the developer and owner required a
cost-effective evaluation of the existing pile capacities to
limit financial impact should the required pile capacities not
be satisfied. Three types of pile load tests were evaluated as
part of the geotechnical design: static pile load testing,
dynamic pile load testing and statnamic pile load testing.
The static pile load test is the most common pile load test
Proposed Pier One building layout and test pile location plan
Reviewing Existing Piles
The geotechnical and structural team initially reviewed the
Massachusetts Building Code to determine if the existing
piles could be reused. Per the code, existing piles can serve to
support new structures if the piles have not been adversely
impacted by the demolition, are structurally sound, have
adequate load-bearing capacity to support the proposed
design loads and meet all code requirements.
As part of the design, the team developed a pile repair plan
to address building code requirements. The code requires that
the capacities of deep foundation elements are evaluated in
one of the following ways: by determining the actual
sustained load that the foundation satisfactorily supported in
the previous structure, by conducting analyses on
documented foundation geometry and presumptive bearing
DEEP FOUNDATIONS * MAY/JUNE 2021 * 17
conducted in geotechnical practice. However, its use was
excluded for numerous reasons: A static pile load test would
require four additional piles to serve as reaction piles, which
would require removing the existing pier deck and a pile
repair at each reaction pile location,
significantly increasing costs and time
involved. And although this test could
have been conducted instead using a
Right: Splash zone-damaged pile at Boston's Pier
One before repair. Below: Prerepair conditions
underneath Pier One (credit: McLaren)
May/June 2021

Table of Contents for the Digital Edition of May/June 2021
