The system of Sheet piling, in which Steel
sheet sections with interlocking edges are used in earth retention and
excavation support retaining soil, has been in practice for many years now.
Sheet pile walls have been used to support excavations for basements,
foundations, below grade parking structures, pump houses, and to construct
cofferdams, seawalls and bulkheads. The technique is simple – sheet piles are
installed in a sequence to design depth along the planned excavation perimeter
or seawall alignment. These sheet piles, interlocked at the edges, form a wall
for lateral earth support with reduced groundwater inflow. For additional
lateral support, anchors also are included sometimes.
The installation of sheet piles is achieved
using vibratory hammers. Depending on the soil, an impact hammer can be used to
complete the installation if it is too hard or dense. If vibrations are a
concern at certain sites, the sheets can be hydraulically pushed into the
ground. The geometry of the sheet pile section and the soils it is driven into
play an important factor in contributing to the performance of the section.
This is because the pressure is transferred from the high side of the wall to
the soil in front of the wall.
Depending on the necessity of the project,
sheet piles can be temporary or permanent. Permanent steel sheet piles are used
in providing a long service life, they remain in the ground to serve as
retaining structures for as long as they can. The temporary sheet piles are
designed to retain only until the project’s end, like in constructions.
Steel sheet piles can also be categorized
based on their manufacturing method. Sheet piles that are formed in a molten
state and rolled flat while still hot are known as Hot Formed Sheet Pile. Sheet
piles that are formed by pressing steel into a sheet in a cold state are known
as Cold Formed Sheet Pile. Hot
formed sheet piles have a variable metal composition and hence are a little
difficult to machine. They are of lesser quality when compared to Cold formed
sheet piles which have a more homogenous composition allowing better heat
conductivity and are easier to machine. Hot formed sheet piles are larger in
size and have a wider range of strengths than cold formed sheet piles.
The interlock at the edges of the sheet
piles is another important distinction between a hot formed sheet pile and a
cold formed sheet pile. Since hot formed sheet piles are produced from steel at
high temperatures, the interlock tends to be tighter than that in the cold
formed steel piles. On the other hand, cold formed steel piles have looser
interlocks. Hence, they are not recommended in extremely hard driving
conditions or for walls requiring low permeability.
Steel sheet piles, both hot formed sheet
piles and cold formed sheet piles, are a sustainable option because recycled
steel is used in their construction and at the end of the project, the piles
can be extracted and the steel can be reused.
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