Geomechanical Musings

The Porter Hotel, Portland, OregonIt’s an exciting time here at Atlas Geotechnical world headquarters. Our decade-long commitment to extraordinary customer service earned us a number of new assignments , seemingly all-of-a-sudden.  We’re leveraging these projects into very rapid growth that requires fundamental changes to our operating systems.  The obvious signs of change: new equipment, robust collaboration technologies, geographic expansion, are all being undertaken in support of preserving, even improving, our earned reputation for responsiveness, innovation, and technical excellence.

You’ll notice over on the Crew page that we have two new Team Atlas members:

  • Jonathan Nasr is completing his Master’s degree in geotechnical engineering at Portland State while working days on geotechnical design and construction monitoring assignments. His initial assignments mainly consisted of developing site characterization models and designing shoring. Presently he’s testing tiebacks at The Porter Hotel project in downtown Portland. While we’re very glad that he’s having the experience of digging a big hole in the middle of the city, we’re sorely missing his office contribution.
  • Wes Miller will join us in mid-March after relocating from the Bay Area to Bend.  Wes has a background in water resources and municipal infrastructure, adding much-needed diversity to our longstanding crew of gearhead geotechs.  Wes is an avid outdoorsman and adventurer, and you can expect to see him on some of the remote projects that are stacking up in our backlog.

There are other changes to the Atlas website, including a number of project descriptions that are long overdue for publication.  The next batch of projects, the ones that we are working on right now, will be even more interesting.

As I write this we have active projects in Guam, Hawaii, California, Oregon, Vancouver BC, northern Alberta, and Michigan. We are solving really challenging problems in nearshore marine construction, ground improvement, storage tanks, impact barriers, and deep excavations. The projects are varied and interesting, our clients are always a delight, and our expanded team is already working seamlessly. In the 12-year history of the company we’ve never had so much new and interesting work. This upcoming 12 months is going to be very exciting indeed.

 

We’ve recently found ourselves working on several projects afflicted by badly flawed numerical modeling.  And not just little errors with inconsequential effect.  These mistakes demonstrate a fundamental misunderstanding about how numerical models work and how to deploy them in Engineering. All of you surely have your own examples of numerical modeling gone awry; here are the two most recent from our practice:

  1. Search constraints in a slope stability model were deliberately set farther upslope than the slope geometry could possibly support, so the Engineer was unwittingly searching for failure surfaces other than the critical surface.  I told the Engineer that the computed safety factor was only valid if the lower (less-stable, light blue) part of the slope could reach up across that little narrow neck at the scarp and grab the upper part (yellow-ish), dragging it down the hill like the caboose on an impossible failure-train.  Yes, we’re interested in the stability of that area back from the crest, but no, forcing the model to violate the basic premise of Method-of-Slices stability analyses does not provide useful insight.Block_Yield Acceleration_Page_1 (2)
  2. Hydrotesting a new canola oil tank caused it to tilt 275 mm across the 36 m diameter. An Engineer was engaged to assess the structural integrity of the tank and, unfortunately, interpreted that assignment as license to run wild with a bunch of structural finite element software. One of the runs showed tank shell stresses 3.5 times higher than the steel strength, which would have caused catastrophic failure before the end of the hydrotest. When I observed that the tank is still standing and the computed result contradicts observed fact the Engineer doubled down on his computations, effectively stating that reality exists in the computer, not the tank.Tank 42

 

It seems to me that modeling failures like these are increasingly frequent as mesh generators and improved interfaces make the software more accessible. The improved speed and efficiency that facilitates competent modeling are just as helpful to the ignorant modelers, allowing them access to new tools that they do not understand and yielding answers that do not represent actual conditions.

I expect that, over time, a few designs based on flawed models will find their way into our built infrastructure. I hope that the resulting losses are only financial, and that before too long we find a way to re-emphasize the proper relationship of modeling in support of engineering, rather than modeling as a time-saving substitute for engineering.

This week between holidays is, without question, my favorite work week each year. This is the week where I clear the decks in preparation for an unencumbered start.  I sort out whatever fussy administrative problem was allowed to linger unresolved in favor of shopping and year-end accountancy. (This year it’s an off-site backup problem; last year was an office furniture need). My white board here at Atlas World Headquarters is full of good uses for this period of predictable calm, and I’ve already started knocking some of them off the list.

For those of you who make resolutions, this is the week that you compose and commit yourselves to making that long-overdue improvement in your practice. Those of us who prefer to skip the resolution stage and simply do the thing, this is the week to make a start and see if the new habit will stick.

We should all recognize how much more productive we are when free of distracting email and conference calls.  Creating such periods of uninterrupted productivity is going to be an important improvement to my practice in 2015, and I would recommend that it be part of yours too. (I use Freedom to turn off teh Interwebs. https://macfreedom.com/  There are many similar programs, and you should use this week to find the one that works best for you.)

Whatever you intend for your practice in 2015, whether you’re still building core competency, diversifying and growing, or starting to contemplate ramping down, I wish you the very best of luck for this preparatory week and great success in the coming year.

TJ Earthquake Damage

Typical Damage at Trader Joes

Friday night’s earthquake in La Habra was interesting for a couple of reasons.

It was small, by California standards, at only Magnitude 5.1.  In fact, I have my automatic notification program set to M6.0 or larger because there are so many small earthquakes like this and generally they don’t cause any damage. I found out about this one through Facebook. So I guess yes, there’s at least one good use for Facebook.

Secondly, the shaking was surprisingly strong for an earthquake of this size.  The rupture was shallow, only 1.7 km deep, and the lack of attenuation up to the surface resulted in  peak ground accelerations as high as 0.25g.  I pasted the USGS shake map below with a handy key to the Mercalli Intensity Scale system of classifying earthquakes.

No serious structural damage occurred, though La Habra Utilities is reporting broken water and gas pipes. The lack of damage and injury speaks more to LA’s excellent building codes and earthquake preparedness than it does to the modest earthquake size. In other parts of the world, places that lack the resources, knowledge, and political will of metropolitan Los Angeles, these types of earthquakes cause fatalities. Intensity VII shaking in California knocks over a stack of wine bottles in Trader Joes. The same level of shaking in rural Afghanistan dislodges roofing stones from their timber supports and buries whole populations in their huts.

Small, generally consequence-free events like these are an opportunity for all of us to reconsider our knee-jerk reactions to troublesome regulations and building codes, a chance for us to give genuine thanks to the smart engineers who led the transition from unreinforced masonry buildings like San Francisco had in 1906 to the well built structures that now protect us from preventable misfortune. Here’s my list of earthquake heroes:

Harry Seed – Pioneer geotechncial engineer and shining light of inspiration

John Lysmer – Smartest good-humored numerical modeler

Vitelmo Bertero – Structural engineer, deep thinker, curmudgeon

CB Crouse – Towering intellect, practical seismologist, mentor

Steve Dickenson – Good friend, collaborator, and insightful earthquake engineer

Yumei Wang – Classmate and dedicated earthquake safety advocate

Jason Brown – Cheerful building code enforcer

Because of their work and the work of countless others, your home and office, your kid’s schools, the bridges that you cross, the port that handles your cargo are all safe from damage in these types of events.

Here’s the link to the USGS event summary, for those of you with interest:

http://earthquake.usgs.gov/earthquakes/eventpage/ci15481673#summary

Be safe, everyone.

La Habra Shake Map

14_03-Oso-8Here at Atlas World Headquarters we’re learning as much as we can about the circumstances leading up to the tragic Oso mudslide. Disasters like that are newsworthy in the US precisely because they are infrequent. We learned hard lessons about floods and fires in the early stages of settling the continent, before our population was so large and had decided to live so deeply in the wilderness. From those experiences, and with engineering input, we created regulations that, most of the time, protect most of the population from natural disasters.

The main problem with this American, reactive approach to safety regulations is that useful safety improvements almost always are adopted after a major disaster, when  death and destruction has already visited a community.  Seismic design provisions in the building code were finally considered after the 1906 San Francisco event, but weren’t adopted in California until 1933.  Double-hulled oil tankers after Exxon Valdez, inspect and repair your levees after Katrina, the pattern is obvious and tragic. In each case there are qualified experts, rational men of science, well aware that tragedy is only a matter of time but who are not taken seriously by the people’s representatives until the “likelihood” of disaster turns into a horrible certainty.

The Oso landslide follows this typical pattern. The hill across the river  is called Landslide Hill, for Pete’s sake. This landslide has expanded in six documented episodes since 1949 and almost certainly predates development in the area. Reasonable people could disagree whether the data foretold  an event like the one that occurred, a 2-stage rotational failure that forced a mudflow across the river to bury the neighborhood. The hazard was known but not with the certainty that could force land use changes that would have saved lives. Snohomish County approved building permits at houses that were plainly in harm’s way and are now under the mud, and the Washington DNR has permitted logging above the slide with only nominal and, likely, ineffective restrictions.

My consulting practice is showing signs that this will change. Sophisticated landowners are now considering the long-term benefits of incident avoidance as a method of slowing regulatory expansion. The political process is not orderly at the best of times and is particularly unpredictable in the face of disaster, when the non-technical electorate is demanding that “someone do something.” Hastily adopted, reactive regulations often overshoot the mark. Since the new regulations cover the entire industry, the entire state, the entire business operation, the cost of compliance usually far exceeds the cost of self-imposed operational improvements that might have avoided the incident and prevented the regulatory expansion.

At Oso, the landowner is a small forest resources company with very low profile, not the group you would expect to lead the industry in operational improvements. They cut timber because the regulations permitted it and they are in the business of cutting timber where permitted. The larger forest products companies in Washington, though, have adopted practices that may have prevented logging above a place called Landslide Hill. Their practices are unlikely, now, to be considered as Washington adopts new logging regulations.

Atlas works in a number of industries with such systemic regulated risk. Liquid and gas pipelines, rockfall, power plants, high-profile infrastructure with significant risk. We evaluate the whole cost of incidents, including natural hazard risk, as it affects our client’s reputation and their operational flexibility. An incident on your line, or even in your industry, has huge implications on new permit applications. The two main Canadian liquid petroleum pipeline operators are managing exactly this risk as they apply for major permits to move crude to market from Alberta. Those pipelines can be built and operated safely, and it would be nothing but bad luck if a small operator with a shoddy record had a preventable incident that, in the view of the non-technical electorate, gave the entire pipeline industry a black eye.

There are other aspects of the Oso disaster that bear further analysis, and we’ll organize our thoughts in a future post. For now, we hope that the responders stay safe through the difficult, muddy clean up, that the community recovers and the road re-opens, and that the forest products industry maintains its voice in the unavoidable evolution of Washington’s logging rules.

14_03-Oso-9

Oso Landslide Overview

For those of you with more interest, the AGU Landslide Blog has excellent technical coverage of this event.

http://blogs.agu.org/landslideblog/

The first hint of logging regulation changes that are, now, almost inevitable in Washington is here:

http://slog.thestranger.com/slog/archives/2014/03/27/is-there-a-connection-between-the-mudslide-and-our-states-historical-mishmash-of-logging-regulations

And those of you interested in model regulations would do well to be aware of Oregon’s excellent Forest Practices Act, which can be accessed here:

http://www.oregon.gov/odf/PUBS/docs/Forest_Facts/FF-LandslidesDebris%20Flows2013.pdf