Geotechnical engineering perspectives and shifting subgrade challenges are drawing more interest as climate patterns change around the world. As we continue our blog series discussion with AOG President Allan Bush, we touch on the influence of changing weather on geotechnical engineering practices in Kansas City and the role of geotech in construction.
Adjusting Expectations and Probabilities.
Even small commercial construction projects are built on sites that can vary underground from one end to the other. The only way to know exact conditions is to examine every inch of an entire site closely. That’s not usually feasible, so geotechnical engineers take small samples to frame up the big picture. They draw on their experience, expertise and judgment to develop a broad understanding based on a little bit of soil.
“We’re taking pieces of the site, getting micro glimpses, to determine the character of the entire site,” says Bush, squinting at pinched soil between his fingers. “We’re seeing what it can tell us about everything going on in the subgrade. Even a rural field that appears obvious and consistent on the surface can vary tremendously down below. You dig in and discover not all the soil is the same and drainage patterns have washed down in different ways.”
Changing weather patterns make variations in the subgrade more likely, whether a site extends across hundreds of yards or thousands. “When you’ve got longer droughts and wetter downpours, geotechs have to adjust their expectations,” says Bush. “Those expectations are everything when it comes to developing recommendations and solutions for getting a project out of the ground in the best way possible.”
Expectations translate to ranges of probability in a geotechnical engineer’s mind. The ranges bookend the potential of likely fluctuations in subgrade conditions. As the weather continues to change, ranges of probability are adjusted. These days, adjustments are becoming a way of life.
“We are constantly recalibrating ranges of probability. It doesn’t happen in sudden, big shifts. It’s fluid, and in the context of changing weather patterns, it’s a subject that gets a lot of attention, not just with engineers, but throughout the construction industry and the real estate industry too.”
Ranges of probability help inform everything from whether a build site is feasible to how quickly construction can be completed, making the analysis of geotechnical engineers increasingly critical to a project plan. If it seems like a subtle numbers game and splitting hairs, think again.
“We’re facing more and more situations where the condition of the subgrade is even changing just between the time of our initial investigation and the start of construction,” says Bush, clicking through a string of recent projects off the top of his head. “We’re writing about laboratory findings from our boring samples and making recommendations based on the data we have when we have it. Then, later, we might find groundwater where we didn’t have groundwater during the investigation.”
Another emerging challenge is the risky assumption some builders tend to make when adding onto an existing structure. Maybe you want to expand your industrial plant to include new buildings or add surrounding office space to your production facility. Bush says new initiatives require new data. If you rely on old data, you’re taking a bigger chance than you may think.
“Basing new projects on old geotechnical reports is a problem that’s going to come with bigger risks as time goes on. New construction plans tied to geotechnical findings from the time when a nearby structure was originally built is not a good idea, but it happens. That’s the hard way of finding out that subgrade conditions have changed since the original report.”
Keeping Construction Away from Destruction.
Not every construction project hinges on geotechnical engineering input. Some builders and owners take their chances in areas of the country where risks seem especially low. But in other areas, you no longer have the option. Climate change is creeping into building codes where the role of geotechnical engineering is increasingly seen as essential. Shifting weather patterns, along with other natural factors, such as earthquakes, are making subgrade conditions a more scrutinized piece of the project puzzle.
“Geotech is seen less and less as an extra,” says Bush. “Back when I started decades ago, knowledgeable builders and contractors were already taking it seriously. But so many others were thinking ‘Geotech, really? Is it important?’ That feeling was pervasive. But now there’s greater awareness and climate change is part of what’s driving that.”
Poor results are a big part of the growing awareness too. Stories of damaging foundation shifts, sinking and even collapse are enough to make a builder think twice about skipping a geotechnical engineer’s insight before digging into a new project.
You’ll rarely come across construction that runs deep into the ground or far across the landscape without the geotech first step. From massive, horizontal structures like the Meritex Lenexa Executive Park to tall structures like the Children’s Mercy Research Tower extending far below the surface, builders are taking no chances.
“Fewer smaller projects are skipping geotech these days too. It’s definitely a trend,” says Bush. “There are just too many variables in the subgrade. It costs much less to check them out and get a grip on them in advance than fixing a problem after construction is complete. No one wants to do that.”
Even lower profile pieces of a project plan are vulnerable and can bring high profile problems if not taken seriously. “Think of pavement,” says Bush. “Whether it’s a road, a parking lot or a freight facility, these are areas with tremendous exposure to the elements. Changing weather patterns must be considered if you don’t want potholes or buckling that take an expensive toll on fleet vehicles and other machinery.”
Avoiding the High Price of ‘Overkill.’
So how did builders through the centuries construct buildings that still stand to this day? They certainly didn’t have the benefit of geotechnical engineering. So how did they do it?
“Overkill.” explains Bush with a smile. “They were smart enough to be extremely conservative. They might estimate the necessary footing for a ten story building and then double it just to be on the safe side — the really safe side. They would put far more money and materials into playing it safe than they needed to because they didn’t want to be even a little unsure of the results. It worked, but it was so expensive. No one can afford that kind of overkill today.”
Bush sees the role of geotech quickly growing well beyond disaster prevention. It’s now about efficiency, developing exact geotechnical solutions for each project to ensure safety and stability without expensive ‘overkill.’ Changing weather patterns are shifting that bullseye. Builders know they may have to invest more in what works, but don’t want to pay for anything beyond that.
“There’s an old saying that an engineer can do for a dime what a fool can do for a dollar,” says Bush. “Geotechnical engineers are now expected to deliver in the face of climate change but without going overboard. That’s where experience serves my team really well. We know how to find that sweet spot in Kansas City’s subgrade.”
What makes that sweet spot even sweeter is when you consider the impact of geotechnical calculations on the rest of a construction project. If a geotechnical engineer evaluates a project site before construction begins, you have the benefit of knowing exactly what you’re working with in the subgrade, and the opportunity to make design changes upfront rather than troubleshooting a big surprise during construction. Just pinpointing the soil’s bearing capacity before construction can mean immediate savings in smaller footings and concrete costs.
Getting a building out of the ground with a solution that’s exactly right is the best use of time, materials and practices. Efficiency is something everyone involved in construction wants. That doesn’t change, even as the natural world does. “Perfecting efficiency is the holy grail. Not too much, not too little,” says Bush. “Climate change is a throwing in a wildcard that’s making customized plans even more important.”
There’s a common phrase overheard in Kansas City, “If you don’t like the weather, just wait a couple of hours.” That’s just the way things go in the heartland. The unexpected is always on the horizon, but even lifelong residents are surprised by changing weather patterns these days. Geotechnical engineering is a key to managing the impact down below. As time passes and conditions evolve, builders will sharpen their focus on geotechs, and the local knowledge and hard-earned experience that uncovers the smartest road to success.