Pipe Ramming in the Thin Air: BTrenchless Goes Large Diameter

I N N O V A T O R S
IN TRENCHLESS
ON LOCATION PIPE RAMMING GRUNDORAM TAURUS
Pipe Ramming in the Thin Air:
BTrenchless Goes Large Diameter
Pneumatic pipe ramming continues to prove that it is one
of the most versatile and effective trenchless methods.
With much of the attention being placed on pipe
ramming’s effectiveness for assisting directional drilling
operations, it is easy to overlook pipe ramming in its
more traditional role of casing installation. BTrenchless
(a division of BT Construction), Henderson, Colo.
recently showed just how effective pipe ramming can
be for large diameter casing work.
According to Mark Wellensiek, BTrenchless Boring
General Superintendent, the company has progressed
from smaller diameter pipe rams to tackling large
diameter projects. He said, “We’ve done about six
pipe rams so far. We started with 24-inch and 30-inch
diameter casings, then completed several 42-inch
diameters and worked our way up to this 84-inch ram.”
For the 84-inch diameter, 80-foot pipe ram under
Highway 160 in Pagosa Springs, Colo., BTrenchless
used a 24-inch diameter Grundoram Taurus pneumatic
pipe rammer from trenchless equipment manufacturer
TT Technologies, Aurora, Ill.
to successfully
c o m p l e t e
projects on time
and on budget.
The company’s
t r e n c h l e s s
c a p a b i l i t i e s
i n c l u d e :
microtunneling
tunnel boring,
hand tunneling,
guided (pilot
tube) auger
b o r i n g ,
h o r i z o n t a l
auger boring,
pipe ramming,
h o r i z o n t a l
d i r e c t i o n a l
drilling, pipe
r e a m i n g
and vacuum
excavation.
For the 84-inch diameter, 80-foot pipe ram
under Highway 160 in Pagosa Springs,
Colo., BTrenchless used a 24-inch diameter
Grundoram Taurus pneumatic pipe rammer.
Company Background
BTrenchless is one of Colorado’s largest trenchless
contractors, offering a variety of trenchless construction
techniques for utility system installations and
replacement of water, storm, and sanitary sewer lines
and conduits. As a division of BT Construction, Inc.,
BTrenchless has over 25 years of utility construction
experience. By maintaining a large inventory of
equipment and employing a large number of skilled
professionals, BTrenchless has the resources necessary
The project in Pagosa Springs drew heavily on the
company’s construction experience and trenchless
expertise.
Project Background
According to Wellensiek, the original CMP multi-plate
culvert installed in 1958 had collapsed. In addition, a
sinkhole was developing on the northeast side of the
intersection of US 160 and 8 th Street. The drainage
casing is part of a larger drainage system that directs
PROJECT PROFILE:
Contractor: BTrenchless
Location: Pagosa Springs, CO
Equipment Used: Grundoram Taurus pneumatic pipe rammer
Specifications: For the 84-inch diameter, 80-foot pipe ram under Highway 160
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un-off from the San Juan Mountain Range, through
town of Pagosa Springs and into the San Juan River.
Continuous flow through the culvert has made the
sinkhole a significant problem. The edge of the sinkhole
was only 25 feet from the north shoulder of west bound
US 160 and the portion of the existing culvert under
Highway 160 was so deteriorated that the Colorado
Dept. of Transportation (CDOT) determined that the
pipe needed to be replaced.
with repeated percussive blows. A cutting shoe is often
welded to the front of the lead casing to help reduce
friction and cut through the soil. Bentonite or polymer
lubrication can also be used to help reduce friction
during ramming operations. Ramming tools, in general,
are capable of installing 4- through 147-inch diameter
pipe and steel casings.
Ramming can be used for horizontal, vertical, and even
angled applications. It is often used under roads, like
the Pagosa project, and rail lines because it displaces
the soil without creating voids or slumps.
According to TT Technologies pipe ramming specialist
Rick Melvin that is a key benefit of pipe ramming. He
said, “Some installation methods can jeopardize the
integrity of roads or rail lines because they remove soil
from underneath to allow for the new pipe installation.
Pipe ramming’s ability to install various sized casings
without putting the topside structures in danger makes
it a very attractive option. Also pipe ramming works in
difficult soil conditions. Boulders and rocks, as large as
the casing itself, can be swallowed up as the casing
moves through the soil and can be removed after the
installation is complete.”
During the pipe ramming process, a pneumatic hammer is attached to
the rear of the casing or pipe.
Wellensiek said, “As the main artery between Pagosa
Springs and Durango, Colo, Highway160 is a very busy
two lane highway and CDOT did not want to impact
traffic by open cutting the highway to install a new
culvert. Open cutting was really never an option. We
would have had to perform that type of work late at
night when traffic levels were as low as possible.”
Ultimately, plans were drawn up to ram an 84-inch
diameter steel casing over the deteriorating 60-inch
CMP culvert and encase it. The existing CMP would
then be removed from the steel casing and a new 60-
inch RCP line installed. The BTrenchless crew would
face many challenges in order to make that happen.
Pipe Ramming 101
During the pipe ramming process, a pneumatic
hammer is attached to the rear of the casing or pipe.
The ramming tool, which consists of a piston within a
casing, drives the pipe or casing through the ground
An entire length of pipe can be installed at once or,
for longer runs, one section at a time can be installed.
In that case, the ramming tool is removed after each
section is in place and a new section is welded on to the
end of the newly installed section. The ramming tool is
connected to the new section and ramming continues.
Several methods can be used to remove spoil from the
casing including compressed air, water, an auguring
system or other types of earthmoving equipment.
High and Not So Dry
One of the first challenges Wellensiek and the
BTrenchless crew faced was elevation. Wellensiek said,
“Pagosa Springs sits at an elevation of 7,100 feet above
sea level. That has a direct impact on the capacity of
your air compressor system.”
Another difficult aspect of the project was maintaining
drainage flow through the existing culvert while
ramming. Wellensiek said, “At times there was really
low flow. Twice during this project we were completely
flooded out because of rain and there was no way to
handle that amount of water. So basically we stopped,
and got out of the way. There was nothing else we
could do.”
On the Job
BTrenchless crews excavated a ramming pit on the
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south side of the road and prepared a ramming pad
by layering approximately 18 inches of inch-and-a-half
rock in the bottom of the pit. Once complete crews
assembled the 60-inch jack and boring machine. The
rails of the machine were used to support and guide the
new 84-inch casing during the pipe ramming process.
Once the casing was placed in position, crews made
the connection between the 84-inch casing and the 24-
inch pie rammer. Melvin explained, “The connection
between the tool and the casing is made through a
tapered ram cone and 84-inch cotter segments. This
configuration ensures that the maximum driving force
is transferred to the pipe. In the past, ramming a casing
of this diameter would have required a fabricated
ramming adapter, but as the demand for larger and
large diameter ramming equipment has increased, we
(TT Technologies) now offer standard ramming gear for
casing diameters as large as 96 inches. This saves
time and money for the contractor.”
According to Wellensiek, removing the existing CMP
pipe was a challenge once the ramming was complete.
He said, “When the new casing was hammered over
an existing pipe we encountered some 30-inch minus
rock during the process. These rocks were pushed
into the existing CMP. In addition, as the casing was
hammered, the ground was compressed around the
existing CMP multi plate. We needed use an acetylene
torch to cut the CMP into 10-foot sections. Then, we
pulled out those sections with the boring machine.”
After the old CMP pipe was removed and all the spoil
cleaned out, the new 60-inch RCP culvert was jacked
into place. Fly ash was used to fill the annular between
the new 60-inch pipe and the 84-inch casing.
Wellensiek was impressed with the results. He said,
“I was really pleasantly surprised that that 84-inch
casing went across there as quickly as it did. The real
challenging part was maintaining the water flow through
there. But now that we’ve gotten through that, we know
we’d be able to do it again.”
Melvin said, “The BTrenchless crew really did a great
job on this project. It was very challenging from start
to finish, but these guys know what they’re doing and
do it well.”
Jim Schill
Technical Writer
Mankato, MN
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Specifications subject to change at any time.