The (not so) solid ground beneath my feet

Today, I’m going to step out of my role as an EE and briefly explore the world of geological engineering. I am, after all, working on a degree in geophysics, and throughout my education, I’ve been exposed to the applied side of geology and geophysics a few times.

One of the reasons I find this field interesting is because I live in a city on stilts.  Fargo is built on top of sediments of glacial Lake Agassiz, a huge prehistoric lake that formed when glaciers melted after the last ice age.  The glaciers melted from south to north, leaving the path to Hudson Bay blocked by ice and the water without a place to go.  This meant that the lake sat there for thousands of years, giving it plenty of time to lay down a layer of silt well over 100 ft. thick.  The silt is clay that easily absorbs water. However, when heavy loads are placed on this clay, the water mobilizes and the clay turns from a very hard mud to pudding-like consistency.  Therefore, while it is fine to build a house, large structures must be built on caissons lest they be consumed by the load-liquified soil.  Prof. Don Schwert at NDSU loves to tell about a grain elevator built near present day Main St. and I-29 that, as it was filled, flipped over and sunk into the soil.  He has also compiled a web page with many images of the difficulties early railroad builders had when constructing lines through the area.

So what exactly do geological engineers do?  They do a lot of things, actually, depending on their specialty.  The overall goal is to assess the geology in an area to provide guidance on issues like where one should build.  They also try to minimize the potential for hazards.  In doing so, they may look at things like the type of rock and soil, the slope on a hillside, or the ways groundwater or flooding may affect building.  In a sense, they are sometimes the opposite of the environmental engineer.  While an environmental engineer tries to understand and minimize the impact of human development on nature, a geological engineer tries to understand how the environment will impact human development and try to find the safest way to do so.  In this process, they will often work closely with civil engineers.

During my grad coursework, I took a class on exploration geophysics, which gives geologists and geological engineers to tools to map subsurface layers.  One of the mainstays of subsurface imaging is, of course, using seismic waves.  However, as an electrical engineer, I was very interested to learn that many of the survey methods involve using electromagnetics.  Measuring currents and fields in the ground can actually tell you how things are arranged underground.  When coupled with boreholes that tell you what is actually down there (but are more expensive), these can be fairly powerful imaging tools.

I greatly appreciate the job that geological engineers do.  It’s nice to know that when I go to watch my favorite team playing basketball the only thing I have to worry about being underfoot is the ball.