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The Citadel breaks ground with new outdoor soils lab
By Keith Plemmons, PhD, PE, PMP
Assistant Professor
Civil and Environmental Engineering Department

          College laboratories are normally thought of as smelly and musty places with students shuffling about quietly in their lab coats and goggles, watching mold grow or dissecting frogs. This is not the case in The Citadel's Outdoor Soils Lab (OSL). Located outdoors with sunshine, fresh air, overlooking the Ashley River in an atmosphere that is sometimes very noisy, the OSL is busy with students wearing sunglasses, hard hats and hearing protection. Despite the differences, the objective remains the same—students learn the practical application of basic concepts and theories.

Citadel students record blow counts and gather around Greg Canivan to watch the pile driving and to observe his PDA analysis.

          The OSL is part of our Civil and Environmental Engineering (CEE) program and provides senior geotechnical engineering students with something they would not normally receive in an undergraduate classroom or laboratory—field experience. To get this field experience, I brought the students in my geotechnical class together with local engineering firms and pile-driving companies to observe and participate in field investigations and pile driving.

Greg Canivan of S&ME demonstrates how strain gages and accelerometers are attached to a steel H-pile.

          As Cadet Jonathan Black commented, "The outdoor soils lab provided invaluable experience by reinforcing topics that were previously only seen in the classroom."

          Located on The Citadel campus, the OSL provides an opportunity for undergraduate CEE students to develop a better understanding of the subjects taught in the classroom. Using hands-on experiences and field demonstrations, the class observes how basic geotechnical concepts apply to everyday practice.

          "You can learn anything in the classroom, but seeing it in the field makes it real," said Cadet Joseph Adams.

          Modeled after the engineering and construction process, the field investigation took place last January, the data analysis and the laboratory tests were performed in February and March and the construction occurred in April.

Michael McCormick from Pile Drivers Inc. discusses pile driving fundamentals with two cadets.

          In January, two local engineering and testing companies set up four demonstration stations. At station one, Soil Consultants Inc. performed a split-spoon sample soil boring with Standard Penetration Tests at five-foot intervals. In addition, several undisturbed Shelby Tube samples were obtained at various depths. At this station, students were instructed on the drilling operations, observed drilling and sampling procedures, and obtained soil samples to be tested as part of their soils lab.

          At stations two, three and four, S&ME Inc. provided demonstrations of the Seismic Cone Penetration Test (SCPT) rig, a Troxler nuclear density testing device, and a speedy moisture tester, respectively. After going through all four stations and to be released from the lab, each student had to walk me through each station, explaining the procedures, application of theory, materials used and other important facts.

          Less than three months after the field investigation, the students found themselves back in the OSL watching Pile Drivers Inc. set up and drive an 80-foot HP 10x42 pile and S&ME Inc. perform Pile Driving Analysis (PDA) procedures. This time they had a personal interest in the outcome. Each student had used the soil profile from the OSL in January to calculate the ultimate bearing capacity of the pile and their results entered into a contest, with the closest answer winning $10 and a case of soft drinks.

          Before the pile driving began, the students gathered around the pile driving rig to be instructed on its components and operation. Also, they were able to watch Greg Canivan from S&ME install the strain gages and accelerometers on the pile and explain how they worked. During the pile driving, two of the students, Joshua Roberson and Andrew Krisel, volunteered to record blow counts, while the remainder of the class watched Greg analyze the PDA data.

          After driving the pile a total of 76 feet and with 30 of those feet driven into the Cooper Marl, the operation halted for 20 minutes to let the pile gain strength. Restriking the pile and analyzing the data, the students were surprised to learn the pile capacity increased from 35 tons to approximately 85 tons. Though no surprise to the experts, the students thought this gain in capacity was magic.

          The Cooper Marl is a thick, uniform layer of highly plastic clay and the primary deep foundation bearing stratum for the Charleston, S.C., area of the United States. Calcareous soil in nature, it is composed of the skeletal remains of microscopic sea organisms, quartz sand, phosphate and clay minerals. Characterized by a standard penetration test N-value range of 10 to 20, it is stiff to very stiff in consistency, olive in color, with a sandy-clay to sandy-silt composition. Open in structure and high in moisture content (40 to 60 percent), the Cooper Marl produces driven piles with relatively small driving resistance. But shortly after driving and as pore pressures dissipate, the capacity gain with respect to time is substantial and yields an economical foundation design. These characteristics of the Cooper Marl account for most of the magic.

          "What began as an idea about moving students from theory and the textbook to give them practical field experience has come to fruition. This is where learning happens. Now we have Outdoor Soils Lab where students can experience important aspects of fieldwork and the process of driving piles. This is a meaningful addition to our program. I want to thank those companies involved for their contribution in helping make this possible," said Dennis Fallon, Dean of the School of Engineering.

          The OSL experience resulted from collaboration among The Citadel, the South Carolina Chapter of PDCA, engineering and testing firms, pile driving companies, and material suppliers. Together they worked to educate the next generation of engineers.

          "The outdoor soils lab was the capstone for our geotechnical classes as it brought the theories and testing procedures to life," said Cadet Jae Mattox.

Author's Note: Last year was the first year for the OSL and it proved very instructive to put companies and students together. In the future, we hope to make additions to our OSL and to demonstrate other aspects of what it means to be a geotechnical engineer. We want to extend the intellectual excitement from the classroom to the field. Being part of a field investigation and developing some idea of what it takes to engineer and construct a driven foundation are experiences that students will long remember. Hopefully these experiences will help them make sound and economical engineering decisions regarding foundation options.

 

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