Drill It In: Student Field Experience

Weeks of planning culminated last Friday in an event designed to give geology students a first look at a drill rig in operation and learn about the process from experienced drilling contractors and geologists (the latter being myself and a Kent State faculty member).  I began organizing the trip after learning about similar workshops provided through organizations outside of the state, in places a little too far for many of our students to attend.  Not that they couldn’t spend six to ten hours of the day traveling…but I’m sure you understand why a nearer location is more appealing.

Students look on as augers advance the soil boring

During this “Field Workshop”, students were able to learn soil & groundwater sampling techniques, how to describe, classify, and log soil borings, the basics of well installation, and basic monitoring equipment.

While the equipment used it typical mostly in the environmental and engineering fields, the basic concepts apply to subsurface investigations in a wide range of applied geology fields including economic geology (natural resource exploration/recovery).

The lead section of hollow-stem auger

The demonstration was provided by a local drilling company, HAD Drilling, Inc., free of charge to our student chapter of AEG.  As such, the activities were limited to a single soil boring which was taken to a depth of only 10 feet below ground surface.  This may seem too shallow to really learn anything and, were this a real project, it would have been.  However, we were actually able to see nice examples of different soil types (clay, silt, and sand), as well as markers such as saturated seams.

Close up of an open split spoon with sample of low-plasticity silt (ML) with med-coarse grained sand at the very end (right).

Drilling is done with a hollow-stem auger (HSA), which is exactly what it sounds like.  During active drilling, a center bit is lowered into the HSA to help drill down and to keep soil from filling in the augers.  Whenever a sample needs to be collected (typically every two feet), the augers are stopped, the center bit is pulled out, and a device called a “split spoon” is attached to the end of the center rods and lowered through the HSA where it is “hammered” into the soil.  The split spoon is essentially a metal tube which can be split in half to easily view and collect the sample.  The hammering process is referred to as the standard penetration test, and is useful in determining a general density of the material being sampled.  This test is standard because a specific weight is dropped (free-fall) from a specific height onto the rod, driving the split spoon sampler into the soil.  Each blow of the hammer is counted, and the number of blows needed to drive the split spoon six inches is called a blow count.  The blow count (or N-value when you use combined blow count values) is what tells you whether the material you’re sampling is soft, stiff, very stiff, etc. (for granular material, you’d say loose, dense, very dense, etc.).

Students inspect a piece of the sample after logging its position in the soil column. Yes, they broke it apart, too.

During this sampling procedure, students were given blank soil boring logs and asked to describe each sample. Initially, they did this on their own and (purposefully) with no guidance.  They then compared “answers” and found that, while most knew they were looking at a clay, other properties of the sample varied – sometimes drastically – between individuals.  When the next sample was collected, they were given a handout which included the Unified Soil Classification System (USCS) as well as a field guide for soil and stratigraphic analysis.  The field guide portion outlined important information to include in any detailed description, such as relative density, color, classification (from the USCS guide), moisture and so on.   Now, most descriptions varied by little from student to student.  By completing this hands-on activity, they were realizing the importance of standard descriptions.

Spectacular scan of the Unified Soil Classification Chart

Groundwater monitoring and sampling methods were also discussed, as well as explaining the significance of “static water level” (aka, the potentiometric surface of the water table; aka, the level to which groundwater will rise when subjected to overburden pressure), how to use the elevations of the static water level in multiple wells to create a groundwater flow map, and how pumping tests and slug tests work to allow a calculation of hydraulic conductivity.

Beginning to draw (expertly, I might add) cross-section of a soil boring and well, as well as explain static water level, groundwater flow maps, slug tests, etc.

This activity was designed as and introduction to some of the processes students will likely encounter upon starting their first jobs.  Even if the exact practice is modified in some way (generally deeper, larger-scale explorations in rock), the basic concepts learned during this workshop can easily be applied to their individual positions.  I did keep this fact in mind throughout the presentation and made it a point to explain differences whenever I could such as how planning where your soil borings/rock cores will be located changes dramatically based on the type of project you are conducting (environmental remediation vs. gas/oil exploration vs. geotechnical investigation).

The whole crew in front of the drill rig (minus the drillers who, not to my surprise, declined the invite to join in).

Ok, this is all well and good, but why do we care to learn about this stuff?  Aside from the attending students wanting to gain a little familiarity with something they might end up getting paid to do, it’s because subsurface investigation is key to any applied geology field.  Of all the course field trips I took as an undergraduate, I can only think of one that even came close to teaching material I’d apply to my job once I graduated.  I have always wished there were more of those trips teaching me what I could expect to do in a career as a _______ geologist (fill in the blank).

Yes, yes, YES!  You need to have an excellent understanding of earth processes, geophysics, geochemistry, hydrogeology, geomorphology, mineralogy & petrology, structural geology, stratigraphy and a whole gambit of other geology subdivisions – some more than others depending on your specific field.  But even with a very strong understanding of the concepts and theory behind it all, the actual practice of getting out of the classroom and observing and doing is invaluable to students nearing graduation and beginning their job search.  That is why we care.  That is why I care and am excited to share this experience with you.

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Special thanks to HAD Drilling for donating their time and labor to giving such a great experience to our group of future geologists!

Extra special thanks to my sister, who volunteered her photography skills for the day and provided us with some great shots (including the ones in this post).  Check out her business, based in the beautiful Shenandoah Valley, Virginia. You can also visit her website: Saraceno Photography & Studios

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