January/February 2021 - 77

The presentation was followed by a
discussion moderated by Silas Nichols,
P.E., where he asked panel members
questions (it included audience interaction through the virtual conference
platform):
Question 1. On the value of
including geophysics:
With several widely used subsurface
investigation techniques available for site
characterization (SPT, CPT, DMT, rock
coring) that can give vertically continuous
profiles and some of which provide samples,
albeit at discrete locations, why should we
routinely incorporate geophysical methods
into our site characterization, and what is
the motivation for owners, developers,
regulators and engineers?
Geophysics can be used to select the
best location or alignment for a project
at early stages, before much is known
about the subsurface conditions. The
geophysical results can be used to focus
where to conduct other subsurface
characterization techniques, and the
geophysical methods can be used to
provide results between the locations of
discrete tests. In situations where
current structures cannot be

demolished or disturbed until a later
phase of the project, geophysics can
provide a nondestructive means to
investigate the existing structures or
subsurface conditions below the
structures. Some geophysical methods
can also be conducted in locations
where access is limited for larger
equipment like drill rigs and excavators
needed for borings and test pits.
Geophysical methods can also be
used in a focused manner during
construction to continue to fill data
gaps, detect changes in subsurface
conditions during construction and
monitor structures once they are
constructed. Geophysical results that
are integrated with standard
characterization methods throughout
the project engineering life cycle can
add significant value to a project by
reducing the need for a more
conservative design to account for
unknowns, can allow for fewer claims
from unexpected conditions during
construction, can improve the ability to
keep projects on schedule, and can
reduce risks for the owner, regulators
and engineers.

Question 2. What is the biggest
obstacle to routine incorporation of
geophysical methods?
With the members of the panel having
different roles on engineering project teams,
what is the biggest obstacle in routine
incorporation of geophysics methods as you
see it?
Educating owners, regulators and
engineers on how geophysics can be
used to benefit projects is an important
step to furthering the routine use of
geophysics for geotechnical
investigations. It is also important for
the project team to include a
geophysicist early in the project to
communicate where geophysical
methods are capable of adding value, to
discuss the limitations of the geophysical techniques so that realistic
expectations are set, and to ensure that
the appropriate methods are selected to
successfully meet the project objectives
during the many phases of the project.
Bad prior experience using geophysics
can also be a significant hurdle in the
routine use of geophysics by some
owners, regulators and engineers. Again,
communication with a qualified

Optical televiewer (OTV) images of fractured Massachusetts bedrock (credit: Hager-Richter)
DEEP FOUNDATIONS * JAN/FEB 2021 * 77
January/February 2021

Table of Contents for the Digital Edition of January/February 2021
