Use of telescoping pile in floating concrete marina design was first conceived by Bellingham Marine in 2006 during the design of a 150 meter long floating wave attenuator for the Royal Sydney Yacht Squadron at Kirribilli near Sydney, Australia.

Since its use at Kirribilli, Bellingham’s telescoping pile has been used on several other projects and is gaining popularity among high end marina owners that are looking for a mooring solution for their floating docks that combines the benefits of a traditional pile system with the clean visual look of a chain anchored dock system.

This distinctive pile features a two part design. The first part is an outer sleeve pile that is secured into the seabed to provide lateral stability. The second part is an inner pile that attaches to the dock below the walking surface to transfer wave and boat loads to the sleeve pile below.

To install the telescoping pile, the sleeve pile is first driven into the seafloor through use of a driving pin. Next, the inner piston pile is lowered by crane into the sleeve pile. The top of the piston pile is secured into a pocket on the pile guide attached to the dock. As the height of the water changes with the tides and storm surges the piston pile moves up and down within the sleeve keeping the top of the pile fixed below the surface of the dock.

Water depth, tidal range and storm surge are critical factors that must be properly accounted for in the design of a telescopic pile. There must be enough of the piston pile inside the sleeve pile at the highest water level to transmit the loads properly. The lengths of the two piles as well as the diameter and wall thickness are extremely important in how the two interact and operate as a single pile.

Although a marina’s decision to opt for telescoping piles is often driven by a variety of factors and may not be a viable solution for all projects, it is a technology that is becoming available to more marinas.  The primary benefit of the telescoping pile is that it performs similar to that of a standard pile system but sits below the deck of the dock.  It can also be used with floating wave attenuators and with dock systems catering to mid to large sized vessels.

If you would like additional information about this innovative pile system and possible applications, please contact Bellingham Marine at bmi@bellingham-marine.

In a future post, we’ll discuss another innovation in pile design that is gaining popularity – the HDPE pile sleeve.