November/December 2022 - 97

* Design codes and owner construct
ion pract ices, or other
requirements, may have changed or
been updated since the time of
foundation installation, and inplace
foundations may have been
" conservatively designed " and could
have excess or reserve capacity to
perform adequately even with
updated design requirements. As an
example, projects where piling is
driven to refusal to bedrock are
likely to have the necessary geotechnical
capacity for re-use as long
as there is available structural
capacity. Static load testing of
existing foundations, not bearing on
a hard layer, routinely finds the
nominal resistance to be significantly
larger than the design value
listed on old plan sheets.
* Foundation reuse could be a viable
option when considered in a risk
registry (applied more frequently in
in construction manager general
contractor/construction manager at
risk projects) with thoughtful
probabilities of realization and
consequences.
* While new construction may
involve added weight or forces to
foundations, original designs can be
reexamined with respect to strength
and serviceability. Effects such as
time-dependent strength gain of
soil may help support new loading.
* For projects over water or where
large structural demands are
supported, foundation construction
(including temporary works) can be
a large cost component; while there
could be savings associated with
installing new foundations and
using longer span lengths, a
thoughtful comparison of costs and
benefi ts can, and should, be
conducted. If sustainability is
included, reuse may become a more
favorable option.
* Inspection can be used to investigate
the integrity of in-place
foundations systems for deleterious
impacts of corrosion and or erosion
of surrounding materials.
* Alternative procurement methods
with a value component may make
sustainability and the related
project benefits more attractive to
owners and contractors alike.
* While some perceive existing
foundations as " risky, " it is important
to note that installation of new
foundations is not risk free: construct
ion qual i ty, equipment
problems, weather, obstructions,
material delivery and multiple
other construction risks apply to all
new construction. They don't apply
to a foundation that already exists.
Building the Future from the
Bottom Up
Within the geotechnical industry, it
would be a worthwhile exercise to
reconsider the costs and risks of
current construction practice, which is
by default building new, with an
increased focus on nonrenewable
resource consumption, emissions,
wastes, cost, time and a more complete
life-cycle impact assessment. While
obviously not suitable for projects with
new alignments or necessary changes
in foundation location, there are likely
benefits and opportunities that many
owners, designers and alternative
delivery project teams have not
previously explored. Those working in
the areas of revision and renewal of
codes and standards should also
consider encouraging sustainable
construction, in this case, the effective
reuse of previous construction.
In the near term, it is likely that
there will need to be industry, professional
organization, owner and
project champions to take the lead.
Awareness of foundation reuse is
certainly an issue for owners, designers,
contractors, regulators and other project
stakeholders. While foundation reuse,
as an element of sustainable construction,
could be considered an
obvious approach, there are both
general and site-specific considerations
that need to be addressed.
Guidelines, codes and standards
need to be reviewed to permit, if not
encourage, foundation reuse, where
viable and appropriate, such that it is
considered at the early planning stages
in project development or when project
requirements are established. As noted
above, development of local guidance is
a practical and likely effective approach
as local guidance can be tailored
to local foundation practices, geology
and integrity threats. Geotechnical
engineers will need to help inform their
structural and other design and construction
colleagues that reutilization
of existing foundations is an option
where it is practical and appropriate,
which may introduce a new type of
field investigation.
There are development needs in the
areas of codes, guidance, best practices
and case history documentation to
support improved industry familiarity
with the practice as well as owner
Static load test of an existing pile
DEEP FOUNDATIONS * NOV/DEC 2022 * 97
November/December 2022

Table of Contents for the Digital Edition of November/December 2022
