Geotechnical Engineering
The beautiful red rock desert surrounding Moab is host to more than 10 geohazards that can affect the structural integrity of buildings, bridges, or roads. We talk with Taylor Hall who is a geotechnical engineer studying the physics of soils and rocks in order to understand their mechanical properties and how they may affect such structures. Taylor has recently started his own business in Moab where he finds the unique environment curious and fun to work in.
Meet the Scientist: Taylor Q. Hall
Taylor Hall is a professional engineer specializing in geotechnical engineering. He grew up in the state of Missouri where he attended the Nevada High School and Missouri University of Science and Technology. After receiving his bachelor’s degree in civil engineering, he attended the University of Texas at Austin for his master’s degree where he studied risk and reliability of bridge foundations. Since graduation, Taylor has provided geotechnical engineering services for both residential and public infrastructure sectors in California, Colorado, and Utah. In May of this 2021, Taylor moved to Moab where he started his own business, the Moab Geotechnical Group. He has experience with a variety of soil and rock conditions but his passions within the geotechnical engineering field are soft soils, slope stability, foundations, ground response, and retaining walls.
When not at work, you can find Taylor trail running around the area with his wife and border collie. He is also part of Science Moab where he will be supporting local students who have an interest in Civil Engineering.
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Interview Transcript - Soil and Rock Stability
Moab is renowned for its biological soil crusts, but what’s happening underneath all that crusty black — with the soil and rock itself? This week, we speak with geotechnical engineer Taylor Hall, owner of the Moab Geotechnical Group, about soil mechanics, engineering tools, and how he decided — at age 15, in a McDonald’s — to start working with the dirt.
Science Moab: What is geotechnical engineering?
Hall: Geotechnical engineering generally deals with rock and soil mechanics and physics: how those materials will respond to structures or just how they respond to gravity. We might look at something like a bridge to understand its foundations, or we might look at a landslide that gets triggered from natural causes. We’re fortunate to be able to come in there and tell you how things are responding and why and what to expect.
Science Moab: How do you test soil?
Hall: When geotechnical engineering got its feet in the 1940s and 1950s, they would sample soil by drilling a hole and driving a sampler into the ground using a fixed-weight hammer. Using that method, we were able to acquire a sample, and get some resistance associated with that sample. That’s much of what we do today, but we do it now because it’s backed by 60 or 70 years’ worth of empirical relationships.
Generally, you’re only dealing with one or two such holes, and you have to use them to characterize a whole site. It’s tough, but that’s why I chose geotechnical engineering: because no two sites are the same. It provides the opportunity to really think on your feet.
Science Moab: Once you’ve taken measurements, how do you adjust your plans and materials?
Hall: It depends on what you’re building, and what you hope that build will be able to accommodate. There might be many different interpretations of how much movement a certain structure can take. It takes a lot of communication; the interpretations and correlations know no bounds.
There are also a lot of cool advancements in soil stabilization. For example, we can dynamically compact soil by literally taking as big of a weight as a machine can pick up and dropping it on the ground repeatedly. That can densify soils. You can also dynamically compact with vibrators and hoppers that put gravel in the ground.
Science Moab: What are Moab’s soils and rocks like?
Hall: This valley is, geologically speaking, unique and beautiful. Being founded on a collapsed salt dome, and having hazards associated with that, create a very curious and fun environment to do what I do. A couple years ago, the Utah Geological Survey put out a hazard-guidance manual for the area, and it came with 13 geological hazards from the Moab environment.
Some of those things are the Mancos shale. We also have “expansive soils”; you introduce a little bit of water, and things can get way out of hand. I’ve seen what we call “swell pressures,” or the load that you would need to put on the soil to prevent it from swelling, that’s on the order of tens of feet of soil. For instance, we have the airport out here, and we’re not going to put down 30 feet of soil just so we can put in a runway. It sparks these unique opportunities to engineer a system.
Science Moab: How did you get interested in geotechnical engineering?
Hall: When I was 15, I was working at McDonald’s with a very well-respected high-school senior. I asked him what he was doing, and he said he was going to engineering school. He explained to me that civil engineers are responsible for making sure all the stuff we often take for granted — running water, electricity, sewers — are functional, and that we have the things we need to go about our daily lives.
At that point, I was like, “I’m going to be a civil engineer.” Then, within the civil engineering world, environmental water resources geotech gave me the chance to be outside. The dirt spoke to me, if you will. One of the jokes I like to tell people is that I grew up playing in the dirt, and now I get paid to do it.
