Tag Archives: Piledriving June 2013

Good friend and Atlas mentor Gary Lee shared this traditional piledriving method with us:

I can’t tell which I like better:

1.  The tambourine used to set the cadence, or
2.  How the penetration rate increased when that last guy jumps up to increase the effective ram weight, or
3.  How the whole human hammer system knew when the pile had reached the design tip elevation.

Because I’m an irredeemable nerd, I estimated the hammer energy like this:

6 guys x 65 kg/guy x 9.81 N/kg x 0.1 m stroke = 382 N/blow

A western interpretation of a small piledriving arrangement.That’s tiny. Absolutely miniscule. It’s about 2% of the smallest diesel hammer that Delmag can supply.  And it got the job done.  Sure, the piles are 80 mm square and are probably reaching a hard bearing layer, and it looks like there several per column.  But that’s exactly the point: compatibility. The site and the foundation and the column loads and the available construction equipment are all compatible, part of a system that is getting the job done.

1.0 m stroke drop hammer with HP14 cap

It reminded me of MacDow’s (http://www.macdow.com.au/) choice to use a drop hammer instead of a modern hydraulic hammer to drive some bridge abutment piles in American Samoa. Simpler definitely is better when working far from a source of spare parts. The drop hammer was slow.  There were some frustrating days.  And it got the job done at a difficult remote site.

This is a project where the design team wasn’t allowed the option of offering a locally compatible design. The funding agency for the bridge insisted that the design comply with North American design standards, which assume essentially unlimited access to the most modern construction equipment in the world. And it was MacDow’s clever and diligent engineers that translated the design, as best could be managed, back to something locally compatible. They used an ancient technology, basically one step up from the “six guys and a tambourine” method, to bridge the gap between our developed-world pile bearing requirements and the actual site location.

The lesson here, the one that amazes me with its rich complexity, is that local engineers and builders already have a compatible system that includes architecture, building materials, construction systems, and life cycle maintenance. Our projects are best when they leverage, rather than supplant, these existing systems. Just because you don’t see a pile hammer on the island, for example, don’t assume that the local builders can’t drive piles to put a building on a soft site. Consider, at least as an alternative, aligning your designs with the local system rather than assuming the project needs you to import a crane, a pile hammer, skilled technicians, and the full logistics train stretching back to New Zealand to build something that, while better or safer, has not been necessary in the community up to the moment you got your contract.

Our friends at Orion Marine Group won a fun little project improving the old Weyerhaeuser waterfront facility for the Port of Everett. The project includes rebuilding the tops of the two existing dolphins and adding a third dolphin close to the wharf.  The photo below (from the Port of Everett website) shows the site, with the two dolphins visible between the two ships that are berthed parallel to shore.

Atlas’ role is pretty minor, just running wave equation analyses, but there’s some really great aspects to the work that I find really satisfying:

  1. The existing dolphins had excellent pile monitoring back in 1994 (by Gary Henderson’s crew at GeoEngineers Tacoma) and so we know a lot about how the new piles are going to drive. I was able to calibrate the new WEAP model to the old driving records before switching hammers and pile types for the predictive runs.
  2. It’s always a treat to work in new terrain.  I have a rudimentary understanding of marine stratigraphy in Puget Sound, but I would not have guessed that the soils are as deep and as soft as I see on the logs.  So I leave the project just a little bit smarter than I started it.
  3. The guys at Orion are always coming up with innovative ideas, and Atlas does our best work for innovative contractors. They have an idea for avoiding a tide-related schedule impact that I’m not sure any other contractor would have suggested, and it’s requiring a very innovative analysis to confirm that it’s feasible.  There’s real money on the line too, which makes the work more engaging.

We’ll wrap up our computations over this weekend and then, if all goes as expected, propose a change to the dolphin modification drawings that could be really beneficial to the Owner and Contractor both. Smart and diligent contractors should always be successful, and it’s a real pleasure to be a part of Orion Marine’s continuing growth.