Geomechanical Musings

My good friend Phil called this week looking for geotechnical engineering support on another one of his interesting tank projects. Phil is an international expert in tank design, maintenance, and operation, and the projects that we’ve worked together have all been career highlights for me.

Storage tanks have the most interesting foundation issues of all structures. On the one hand, a structure completely full of liquid is orders of magnitude heavier than a structure full of air and people and office furniture. Only steel mills have higher loadings. On the other hand, though, the structures are extraordinarily flexible, at least in many ways, and can often accommodate settlements that the heavy loads induce. So deflection management, rather than avoidance, is the design goal. I’ve been inside tanks in Mississippi that look like skateparks on the inside, and where the interior support columns have threaded rods sticking through the roof so the columns can be lengthened with a torque wrench while the bottom plate and foundations settle.

These particular tanks, the ones that Phil called about, are being retrofitted to allow higher interior pressure. Even a couple of lb/in2 inside a tank 200 feet in diameter creates a huge force. The bottom plate is flexible, which is a good thing, but in these tanks the shells and annular rings are not anchored to the ringwall foundations. So adding pressure to the tanks will inflate them like a very stiff, very expensive balloon and lift the shell off the foundation. The engineering task is to design reliable, economical anchorage to resist uplift forces around the tank shell caused by increasing the tanks interior operating pressure. It’s not a large project, but the people that I get to work with and the practical solutions that I get to develop make these small projects some of the most rewarding.

We’ve been slammed this past month here at Atlas Geotechnical World Headquarters with two interesting and completely different dispute resolution projects.

The first, and more conventional, involves piledriving problems on a highway bridge project. (The photo on the left is not from this project. These piles are in Diego Garcia. I just like pictures of pile cushions burning). The highway job was big and the problem very well documented, and my involvement started with the customer DropBoxing me about a hundred PDA and CAPWAP reports. Yes, I did in fact do a brief joyful dance when presented with all that gorgeous data.

One fascinating aspect was that the project changed delivery methods, from Design/Build, to Bid/Build, but the B/B contract retained the D/B design. Reviewing the data offered me an unusually clear view of how engineers, appropriately, alter their design approach depending on the level of involvement they expect to retain during construction.

The assignment was straightforward: read all the materials, do a bunch of analyses, and figure out why piledriving was so difficult. It culminated in a report, which I was able to prepare on an accelerated but still manageable pace.

The second project could not feel more different. It’s a rainstorm-induced slope failure that closed a road and damaged both public and private property. (And no, it’s not the landslide on the right. That one is on Highway 1 and is a much bigger problem.) Mediation was not successful, and Superior Court rules move us rapidly to trial. While I support prompt resolution of failure issues, the pace makes thoughtful analyses challenging because none of the experts have produced reports. All parties are learning about findings and conclusions through depositions, and the deposition process does not facilitate coherent narrative. I’ve been attending the sessions that have geomechanical topics so that I can digest the verbal description of other expert’s assumptions, methods, and conclusions before immediately translating from jargon to legal so that my client can ask insightful questions. While the pace of the work is similar to the piledriving problem, producing expert advice without mulling over a written draft, even briefly, completely changes the feel of the work. A completely different skill set is needed, the ability to simplify and reduce, as opposed to the ability to carefully and thoroughly explain.

Interestingly, Atlas’s fees on the this landslide issue are roughly comparable to the fees on the piledriving matter, but the piledriving damages are more than two orders of magnitude higher. It seems like a direct comparison of efficiency: the piledriving issue has hugely more data that was neatly summarized in a group of generally similar reports. The slope failure project is dribbling out technical data in no particular order in the course of daylong question-and-answer sessions.

I think we should all be thankful that our society provides a formal and binding method of resolving disputes. Much like representative democracy itself, the process can seem inefficient and sometimes even unfair. But at least there’s a process with predictable rules, and the inefficiencies seem on the whole acceptable given the alternatives. Offering deposition testimony without having already formulated, refined, and produced a report summarizing my opinions was very different from the piledriving problem, where my written report reduces the possibility of mis-speaking, making a muddle out of a technical explanation, or leaving out important supporting information. In addition to the expected favorable results for both my customers, I’ve grown professionally from the experience of working two projects that should have seemed similar but where differences in pace and process caused them to be completely different.

I had the great pleasure to spend the first part of the week working with Bruce Lane of Precision Measurements, pushing really hard on the ground and measuring really carefully. I was in Portland, Oregon validating a simple but innovative ground improvement design before greenlighting production installation.

The project is a classic Pearl District apartment building, 5 stories of wood-framed residential over 1.5 levels of concrete basement. Soils at the site are pretty soft, but good dense gravel is available shallow enough that driving piles seemed excessive. Working with DeWitt Construction, Atlas Geotechnical designed a system of low-strength concrete shafts that improved the bearing capacity enough to support the building on footings instead of costly piles.

Engineering, especially innovative engineering, is all about getting the details right. All of the details, not just to obvious or convenient ones. Bruce is an indispensable part of confirming that the concrete shafts behave the way that we predicted in the design.

Bruce is one of those rare individuals capable of performing very sensitive work very accurately away from a controlled laboratory setting. This set of skills is slightly more common where we practice, in the heavy infrastructure industry, but is by no means common. You know you are working with professionals committed to quality when they tell you about how they stripped and waxed their hydraulic cylinders because the paint was always chipped and looked shabby in the report photographs. Of course the data needed to be complete and correct, and standard procedures rigorously followed, but taking the time to polish the equipment for photos indicates a commitment to excellence that seemed very familiar to us here at Atlas.

Bruce has the skill, experience, equipment, and patience to get the kind of high-quality data that instills confidence in a design, allowing safety factors to stay in the acceptable range and construction to proceed apace. And if you ever do have an unexpected result, Bruce can identify the cause while it’s developing, often modifying the test procedure to collect insightful measurements, so you know where to focus your attention when revising the design. This is a crucial aspect of the “Observational Method” that forms the backbone of Atlas Geotechnical’s expertise, and in fact is one of the most difficult to obtain.

We had great success with the validation program, demonstrating the necessary strength and stiffness while also seeing real failures that demonstrate we didn’t have excessive conservatism in our design. We even had a failure, but of a reaction element and not the test element itself, that Bruce caught before the reaction frame became unstable and dangerous. Working with Bruce, the DeWitt Crew, and really everyone on The Parker project made for two excellent days of work, and having bright sunshine in February, good friends extending hospitality, and really excellent beer after work made the trip an overall brilliant experience.

I really do work with the best crew in the world.

The most recent reminder is the note I got this afternoon from Peter Jacke at Cooper Testing. Along with notifying me that my results had been posted (ahead of schedule), he wanted to be sure I knew that there were three specific gravity tests that he had assigned on his own initiative and for which I would not be charged.

The tests were necessary, in Peter’s judgment, because some falling head hydraulic conductivity tests were returning low saturation values and the most logical explanation was that the soils from our Maui site were heavier than typical tropical soils. For those of you keeping score at home, the results were 3.05 to 3.09, 15% higher than the typically assumed value.

The point here is not that Peter ran extra tests for free. The point is that Peter and his crew at the lab saw results that didn’t seem right and took unilateral initiative to satisfy themselves that they were delivering results consistent with the quality standards we all expect from Cooper Labs. Their in-house quality checks raised an issue, they resolved it quantitatively to their own satisfaction (upon which I rely), and they sent along the results just in case I could find another use for them.

What a great object lesson for all of us, especially those of us who aspire to the same reputation for quality that Cooper has earned over the past decades. Quality comes standard on every project, and when you need to do a little work to assure that you’re delivering quality, you do the work without expectation. This is how you earn long term customer loyalty and repeat business, everyone.

Well done, Peter. Thank you.

Reputations accumulate through consistent excellence in each interaction, each conversation, each deliverable. The Atlas GT holiday card design makes an excellent example. Cosmic Design (http://designbycosmic.com/) accepted the small, marginally interesting assignment even though their plate was full and Thanksgiving weekend was imminent.

Along with an artwork proof, which I expected, Eric included this carefully composed photo of the mockup. Take a minute to look that the photo: it’s well composed, has interesting focal depth, and the color has been modified to accentuate the theme . Work went into this photo, care and attention to detail not normally warranted by an interim proof. And yet it gives the impression of effortless cool. Cosmic, again, exceeded my expectations, increased my enthusiasm for the project, and cemented another building block onto their already significant reputation.

It’s hard to focus on fine details when we’re pressed for time. Yet the value of such attention to detail is much higher than the few minutes saved by cutting corners. I’m hopeful that we can learn from Cosmic’s example that reputations for excellence are built in small, incremental, but ultimately very valuable steps.