Geomechanical Musings

Seattle imposes a local requirement for verification testing of shoring tiebacks in addition to proof and performance testing. Because the required test load is 2.0 times the design load, and our design safety factor is 1.5, the test is almost certain to fail the anchor on the soil/grout interface.  At least, if our design achieves the target conservatism, the verification test ought to fail the soil/bond interface; otherwise our strength estimate is low and our design is pointlessly conservative.

One charming aspect of such high test loads is that verification anchors need additional strands in order to safely transfer the test load down to the bond zone. (We prefer to test a typical bond length with extra strands rather than use a typical strand count and shorten the bond length.) that means that the test anchors look really robust. The anchor below is only a 180-kip anchor, but it has 9 strands because it’s going to be tested to 360 kips.

Another fun aspect of testing sacrificial anchors is that they need to be installed in between soldier piles so they don’t take up the pocket for a production anchor. That means that we get to use a cool reaction frame for the test. Setting the frame is an extra step, but I think it makes the test setup look super old-school.

Really, though, the point of this post is just to share the photo that Wes sent down from the jobsite. The test results, to be honest, were disappointing.  The setup is really clean and efficient, though. We’ve already installed a similar anchor and then post-grouted it looking for higher capacity. I expect that later today we’ll have a similar photo of a great looking verification test and also proof of the high strength we used in our design.

Is it just us, or does it seem like earthquake activity has been particularly high this summer? Even while I’m writing to talk about a fascinating photograph of slope failures in Hokkaido, but also this morning was another major event near Fiji.

For those of you just interested in the photo, here’s a quick link:

Mudslides in a wide range by magnitude 6.7 earthquake(Atsuma, Hokkaido, Japan) from CatastrophicFailure

Here’s the link to an article about the Hokkaido event and also, I believe, the photo’s source:

None of those failure are on the scale of the Oso landslide in Washington, but the cumulative volume is quite considerable. Thankfully the terrain is so steep that the area is sparsely populated.

So far this summer damage has been generally modest despite some of the earthquakes being quite large. Let’s just hope that it continues that way.


It’s been an interesting week here at Atlas Geotechnical World Headquarters. Our project in Seattle is standing down while Equipment Operators Local 302, who struck last week, continue negotiating a fresh labor agreement with the Associated General Contractors. Three timezones to the left, our project supporting new friends WW Clyde Company in Hanapepe is shut down by Hurricane Lane.

The hurricane, and attendant drenching rains, are on my mind because this afternoon’s task is analyzing hydraulic rise caused by installing bulkhead walls that allow driving access out to the in-water bents. Crane loads during demolition and foundation drilling are legitimately heavy, and the site is crowded, so getting equipment into position has turned into a significant effort.

I include some snapshots from my visit to the site last week. The existing bridge is a graceful reminder of classic Corps of Engineers construction. Built in 1938 for the Territory of Hawaii government, it’s provided reliable service for more than 8 decades.  The replacement bridge will be higher, wider, and safer.  Plus it’ll be free of the weight restriction that is causing difficulties for the re-opened aggregate quarry just a couple of miles up the road.

The temporary bridge is already in place, courtesy of Hawaiian Dredging Company, though the connecting diversion embankments remain for WWC to install.  Our good friend Gary Coover at Pryzm Consulting has the lead on geometric roadway design and utility relocation onto the temporary bridge.  We’ll lend a hand with a very narrow MSE embankment design, but we’ve also got our hands full with crane access designs for demolition and construction.

One last note:  The pipe piles in the photo at right, which support the temporary bridge, were intended to drive 40 or 50 feet into the “compact mud-rock” stated on the 1937 boring logs (I do so love the very effective diction in older plansets). The existing bridge is supported on untreated timber piles 35 to 40 feet long.  Surprisingly, PDA testing during of the pipes showed very low capacity through that known bearing layer.  The pipe pile in the photo is 140 feet long, as long as the planned new bridge shafts. Work in the Islands is just filled with surprises.

Everyone stay safe through the storm, please, and we’ll pick up where we left off once the floodwaters recede.

I had an excellent week with TransCanada up in Fort Hills, north about an hour’s drive from Fort McMurray. We were working in the tank containment of their Northern Courier Project (NCP) terminal, the north end of the pipe that conveys hot bitumen south to Hardisty terminal, from where it makes its way to refineries in southern Canada and the US. I had a chance to support the hydrostatic tests on these tanks back in 2016, and it felt great to be back in Fort Mac, and the hospitality I received could not have been more appreciated.

I’m used to fielding sincere questions about how I feel working in the oil-and-gas industry, and this trip led me to reflect more carefully on my reasoning. There’s a valid argument about the side-effect consequences of making this energy available to American consumers who are not particularly skilled at using mass transit and not motivated to purchasing energy efficient vehicles. I acknowledge the merit of arguing that cutting off the supply of oil would accelerate the inevitable adoption of renewable and other lower-impact energy sources. If only it could be accomplished so easily…

What’s lost, though, in this (sometimes heated) discussion is the extraordinary commitment pipeline companies make to operating safely and maintaining containment integrity. And since a company is really just a group of engineers and operators united by management and culture, it’s not surprising that the oil-and-gas industry is home to the most diligent and thoughtful engineers with whom I’ve ever had the pleasure to work. They are, each of them, resourceful, bright, collaborative, safe, and well-trained. This past week in Alberta was a great reminder of engineering excellence under sometimes difficult conditions. It’s astonishing, and I can’t relate how much I enjoy working with them.

We completed our work safely and effectively, and I departed with the Operations group fully in control of a situation that, honestly, was never particularly challenging.  The idea of diligence is fully ingrained in their culture; they understand the consequences of a problem and are diligent in investigating every anomaly to assure that no issue escalates into a problem. I look forward to my next opportunity to support this excellent organization.

I spent a very pleasant Saturday morning with the GeoStabilization crew as they wrapped up shotcreting the face of their Lower San Antonio Road landslide repair while I ran the nail capacity performance test.  The site is surprisingly far east to still be in Santa Clara County, past Lick Observatory by almost an hour on a beautifully scenic winding road. The test setup is pretty simple, as you can see above, and the loads are modest enough that simple cribbing on soil provides enough reaction force.  We’re really enjoying this on-call collaboration with GSI and I’m angling for a way that I can cover the next testing assignment.