Underground Construction - May 2019 - 26

Hidden Beneath the Bed
option would be to fabricate a tool to cut the
wooden pier out of the casing's path, then
continue ramming operations.
Future construction plans required the line's
path to remain as specified. The owner and general contractor favored cutting away the pier
to continue as planned. Carter and Wafer modified a standard rock-cutting head to make it
an efficient wood-cutting tool for the augering
machine. The tool's design included the ability
to expand once it exited the 12-inch casing
and retract again to facilitate its retrieval. It
worked perfectly, cutting a hole wide-enough to
permit the casing to easily pass through. Crew
members backed the tool out of the casing and
resumed pipe ramming operations.

Not long after they had started, they ran
into a second pier. Once again, they pulled
the ramming tool away and repeated the
cutting process.
When they resumed pipe ramming
operations for the third time, advancing the
pipe to 80 feet, they were stopped again. This
time the sounds coming from the pipe were
different than before. They backed away the
ramming tool and collet once again to set
their auger on the rails, remove spoil from
the casing and send a video camera down to
inspect the obstacle. This time the hole was
blocked by a discarded manhole cover. Not
far from it, they learned, was an abandoned,
reinforced-cement manhole.

Kinnan modified a standard rock cutting tool to cut through wood. The tool's cutters expanded once
past the pipe end to cut a hole wide enough for the casing to pass through.

Railway traffic continues completely unaffected by the pipe ramming operation.

MAY 2019 | UConOnline.com

Starting over
If they were to stay on the specified bore path,
the only option left was to dig the manhole
out. They had advanced the pipe clear of the
track above it by 15 inches, but the railway
would not permit them to excavate through
the bed's formation.
That left just one alternative. Kinnan must
offset the bore path and begin again, staying as
close as possible to the original specification.
The crews left the 12-inch casing in place, filled
it with grout, and moved ramming operations
two feet to the side to miss the steel obstruction and the wooden piers. As an extra precaution to avoid a submerged pipe associated with
the abandoned manhole, they modified their
pit, giving it a downward grade of 3 percent.
Kinnan crews sent the dummy pipe across
this time without any issues. They pulled
the pipe back using their auger-boring
machine, completing the gas line installation
for their customer despite the repeated
complications, entirely within the daily work
window and without ever interrupting railway
or commuter traffic.
It isn't the first time Kinnan found hidden
surprises beneath the tracks, many posing
daunting obstacles for those less-familiar with
railroad applications. Mike Walk, a pipe-ramming application expert with HammerHead
Trenchless, said even the use of ground-penetrating radar (GPR) cannot adequately identify
whether an object in the pipe path would stop
a pipe-ramming operation. Nor is it a common
practice to employ GPR in railway crossing jobs.
Regardless of the preliminary documentation they receive and their own routine
exploration of a planned bore path, trenchless
pipe installers around the country have found
everything from discarded appliances to entire
buried boxcars. "You just never know what
you'll find beneath tracks," Carter said.
While these may pose formiddable obstacles
for those less familiar with railroad applications, in over 20 years of trenchless installation, the obstacles that Kinnan crews have
encountered have never resulted in failure to
complete an installation.
Carter said that Kinnan may, indeed, one
day encounter subsurface obstacles that may
prove impossible to overcome. However, he is
confident that any pipe-installation contractor
competent in a wide variety of trenchless
methods and using quality equipment
matched to the specific job will find a way to
complete almost any pipe-ramming project.
Experience and capability of on-the-spot
innovation boost expectations of success. *

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Underground Construction - May 2019

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