One of the oldest debates in the pile driving
industry has been the use of hot-rolled
sheet pile or cold-formed sheet pile. Hotrolled
sheet piles typically have a ball and socket (i.e.,
PZ or PZC) or Larssen-type interlock (i.e., AZ, NZ
or Hoesch) while cold-formed sheet piles have a bent
plate type interlock (i.e., SKZ, XZ or MSZ). Each
type of sheet pile offers advantages depending on your
application. Here’s our list of the advantages of each
type of sheet pile:
Hot-rolled sheet pile advantages
1. Interlocks are more durable
In order to make a hot-rolled sheet pile interlock, the
steel is heated to more than 2,100 degrees Fahrenheit,
which is then sent through a rolling mill. By having
the steel malleable, the hot-rolled mills are able to
manufacture more complex interlock shapes (i.e., ball
and socket or Larssen interlocks) than the simple plate
bending of a cold-formed sheet pile. This manufacturing
process produces an interlock that is more durable,
which allows for driving and pulling the sheet pile multiple
times before the interlocks are worn out.
2. Better suited for hard-driving
Hot-rolled sheet piles have tighter and thicker interlocks
than cold-formed sheet piles. These interlocks
have greater steel thickness and are better suited to
handle the driving stresses of harsh ground environments.
Due to the loose interlocks of cold-formed sheet
piles, manufacturers like Skyline Steel do not recommend
their use in extremely hard-driving conditions.
3. Higher recycled steel content
LEED requirements sometimes dictate the use of recycled
materials. Hot-rolled sheet piles have 100 percent
recycled content while cold-formed sheet piles typically
consist of 80 percent recycled material.
4. More watertight
Hot-rolled sheet piles perform better in seepage tests
than cold-formed sheet piles. This is because the hotrolled
sheet pile interlocks have more and tighter pointsof
contact when driven. Also, hot-rolled sheet piles are
produced from forged steel at very high temperatures,
which makes the interlocks tighter. However, both
types of sheet pile interlocks tighten up over time as
sediment builds up in the interlocks. Additionally, sealants
can be added to both hot-rolled sheet pile and coldformed
sheet pile to increase water-tightness.
STEEL
Cold-formed sheet pile advantages
1. More readily available
Cold-formed sheet piles are produced by more mills
than hot-rolled sheet piles, due to the cheaper investment
in equipment. This increases the number of rolling
dates to choose from. Typically, cold-formed sheet
piles can be available within two weeks from the time
ordered.
2. Cost-effective
Due to cheaper equipment investment required to
manufacture cold-formed sheet pile, they are typically
30 to 40 percent more economical than equivalent hotrolled
sheet piles.
3. Cheaper transportation
Since there’s a greater number of cold-formed sheet
pile manufacturers, there is a better chance that a mill
will be located closer to your job than if you were to
purchase hot-rolled sheet piles. In addition, there are a
larger variety of cold-formed sheet pile sizes, allowing
you to get a sheet pile with a section modulus closer
to your design without having a substantial increase
in weight.
4. Greater flexibility in positioning sheets
Cold-formed interlocks allow the sheet piles to be rotated
up to 25 degrees instead of the 7 to 10 degree rotation
allowed with the ball and socket interlock. This
can eliminate the need to purchase extruded pile connectors
to round corners.
5. Complementary interlocks
The radius of the bent interlock is hinged upon the
steel thickness, which means most cold-formed sheet
pile of similar section will interlock – regardless of
manufacturer. In comparison, if you have a Larssen
interlock sheet and a ball and socket sheet, the only
way you will be able to connect them is by purchasing
or fabricating a special connector.
As you can see, there are certainly advantages for
using both types of sheet pile. Oftentimes, it comes
down to the preference of the engineer or field personnel
driving the piling that will be the determining
factor on which type of sheet pile is to be installed. t
Andrew N. Norman is chief operating officer and
co-founder of Eiffel Trading, LLC. Contact him at
anorman@eiffeltrading.com.
There are certainly advantages for
using both types of sheet pile.
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