Objective: Build a form clamp that enables single-lift injection of jacketed H piles.

Highlights:

  • Designed, tested, and used new extrusion
  • Enjoyed easy underwater use of new lightweight clamps
  • Performed 240 successful pumps in one job with new clamps, without a single jacket blowout
Project Details:

FRP jackets utilized for H-pile encapsulation cannot be injected without reinforcement.  In order to successfully inject an H-pile encapsulation, a rigid clamping mechanism that applies force to all sides needs to be installed.  Substructure has developed a series of high quality form clamps to fill this need.

The main difficulty in epoxy pumping H-piles is jacket bulging.  On round piles, a consistent loop tension at each elevation prevents blowouts, however the same forces acting on the flat surfaces of H-pile jackets deflect the jacket at different rates for the size of each of the 12 flat surfaces.  Such inconsistent deflection frequently result in “blowouts,” the loss of jackets, and excessive use of epoxy.  Before Substructure designed and built H-pile form clamps, one of the only ways to combat this was through multiple lifts per jacket, slowing productivity and creating an inferior encapsulation.

Substructure engineers developed two custom extrusions that would be used as the main components of the clamps, and then conducted finite element analysis testing to demonstrate the clamp’s structural integrity.  Expansion bolts in the H-pile web provide appropriate force to the smaller extrusion to maintain the jacket’s shape.  The larger extrusion, which was designed to have greater strength in the center of the flange, maintains the structural integrity of the jacket on its largest faces.  Specific supports were fabricated by Substructure welders to reinforce areas where jacket “blowouts” statistically would occur most frequently.  All voided areas of the clamp were completely sealed to produce a semi-buoyant finished component.  In designing, simplicity of use was a high priority to facilitate rapid installation underwater.

All of these design elements resulted in a rigid form clamp that produces consistent encapsulations.  Due to the rigid and encompassing nature of these jackets, H-piles could be injected in a single lift, creating a monolithic structure.  Substructure successfully pumped 240 steel H-piles with these form clamps over a four-month period without a single jacket blow out or failure.