What is an O-Pile system?
An O-shaped sheet pile is a pipe section with attached connector sections so that one section can be driven into the next to form a continuous steel wall with the same load bearing element.
The connector sections are connected together through an interlocking system. Eurocode 3 BS EN 1993-1995: 2007 Section 1.8.12 defines interlock as:
The portion of a steel sheet pile or other sheeting that connects adjacent elements by means of a thumb and finger or similar configuration to make a continuous wall.
According to BS EN 10248-2 (European version of ASTM), “Interlocks shall have adequate free play, so that the piles can be fitted into each other and they must engage in such a manner that the in service forces can be transmitted.” For non-flat sheet piling such as the interlock connecting system in contiguous o-sheet piling, BS EN 10248-2 also allows for a 4 mm minimum engagement distance in the interlocks in order to effectively transfer forces.
It is important to note that hot rolled sheet piling has this minimum engagement distance of 4 mm while cold formed does not necessarily. This is why cold formed does not always transfer shear forces as effectively as hot rolled sheet piling.
US Army Corps of Engineers Unified Facilities Guide Specifications Document UFGS-31 41 16 page 13 notes: “interlock connections between hot rolled sheets provide much greater strength than cold formed connections. Greater interlock strength improves integrity during driving and allows forces to be redistributed laterally along the wall at changes in wall alignment…”
Why use an O-Pile sheet pile system?
Because we can take readily available pipes and begin a project to meet/exceed virtually any steel sheet piling requirements and begin delivery a ready to install system in days versus months.
How are z sheet pile and the O-Pile system similar?
They are both contiguous walls and hence much easier to install than a combined sheet pile wall.
Can you build an O-Pile wall with grade 80 or higher steel?
Yes, unlike hot rolled or cold rolled sheet pile systems that are limited to aboout grade 65 and most often produced with grade 50 steel, Pipes can be produced in higher grade of steel there-by giving the user is much higher bending moment per pound of steel.
What is bending moment important?
The best method for comparing SSP is via bending moment capacity, which incorporates the strength of the section due to its geometry (section modulus) and takes into account the steel grade: Bending moment capacity = elastic section modulus [m3/m] × minimum yield strength [kN/m2] (without safety factor) The BMC of a sheet pile section with a section modulus of 4019 cm3/m in a Steel Grade of S 355 is: 1427 (kNm/m) = 4.019 (m3/m) x 355 (N/mm2) The BMC of a sheet pile section with a section modulus of 2290 cm3/m in a Steel Grade of X70 is: 1111 (kNm/m) = 2.290 (m3/m) x 485 (N/mm2) Decades ago, when there was predominantly only one steel grade, engineers used section modulus as the main design criteria. But now that many steel grades are available and production technology has evolved, we will likely see more and more higher grade steel options in the future. A higher grade of steel results in a stronger wall for less weight; thus, the best measure of strength to compare SSP systems is bending moment capacity, which incorporates section modulus and steel grade into one number independent of lifespan or safety factor. Incidentally, moment of inertia has no relationship to bending moment and is not typically a stand-alone criteria. Certain steel companies have pushed for moment of inertia to be placed as part of a primary specification and have, as a result, confused the term with the vital bending moment.
Where has the O-PIle system been used?
US, Canada, Japan, Russia, Ukraine, Norway, Finland, Sweden, Philippines and many other places.
Has the US Navy build an O-Pile system?
When should I consider using an O-Pile system?
a) When you need a sheet pile section that is stronger than a Z 40 level under normal soil conditions.
b) When you need to install a wall into rock or boulders and you can not install a z sheet pile.
C) When you have heavy loads where by filling the O-Pile with sand or cement increase the untiliy of the sheet pile system.
D) For temporary applications, as you can reuse the O-Pile system easily.
E) When you would like a sea wall to last a long time and be cost effective. You can make an O-Pile thicking in the zone of high attack the top section of the pile and also eliminate the need to coat the steel.