It's before 7 a.m. on a warm summer morning, and engineering student Fernando Andrade Orellana Alves is already at work.
In a clearing across the Susquehanna River from the Bucknell University campus, Alves attaches an auger to a blue drilling rig with orange letters spelling Bucknell vertically down its mast, then watches as civil engineering lab director Jim Gutelius guides the spinning drill into the ground. As the auger reaches a depth of 5 feet, Alves grabs a pipe wrench, and with Gutelius bends his back to break the auger free from the drill rod. He grabs the next section of auger, and guides it into place as the mast of the rig raises it high. The process repeats until the crew hits bedrock, some 30 feet down, and Alves, Gutelius and Professor Mike Malusis '93, civil & environmental engineering, can set an inclinometer into place — one of dozens of sensors they'll install at the site in the coming weeks.
While Alves, an exchange student from Brazil studying civil engineering, will be returning to his home country soon, he's helping to construct a first-of-its-kind field station that will enable multidisciplinary research and student learning for many years to come. It's also giving him a close-up view of engineering in action that he never had, even after five years of engineering education in his home country.
"In civil engineering, you can design structures or you can work in the field," Alves said. "Here I can gain practical experience of that work. It wouldn't be possible for me to do that in Brazil, where no university has this kind of equipment. To me, it's amazing."
The work Alves is doing is part of a National Science Foundation-funded research project led by Malusis; Professor Jeffrey Evans, civil & environmental engineering; and Professor Rob Jacob '97, geology & environmental geosciences; with assistance from Gutelius and Professor Alan Marchiori, computer science. The $380,000 grant enabling the project was awarded in 2015, with construction taking place this summer, and will continue for two more years. But the field station will enable long-term studies continuing for a decade or more, providing many additional experiential learning opportunities for students like Alves.
What they are building is a common structure installed thousands of times around the world: an underground vertical barrier — known as a soil-bentonite cutoff wall — used near factories and landfills to prevent waste and pollution from contaminating groundwater. It's constructed by digging a trench, mixing the excavated material with a slurry containing water and a clay called bentonite, and backfilling the trench with that mixture. Despite their ubiquity, how well these barriers perform their intended task over time remains largely unstudied, Malusis said. Theirs is the first such wall constructed solely for research purposes, he added.
"We need a better understanding of the conditions at the time of construction, how these conditions change with time, and how their performance may change as they age," Malusis said. "In many cases, a cutoff wall is supposed to function, essentially, in perpetuity. As time goes by, we need to know that the wall is still going to be functioning the way it was designed."
To answer these questions, the researchers are outfitting the wall, which is approximately 650 feet long and 20 to 30 feet deep, with sensors that monitor groundwater levels, settlement, water pressure, suction and other stresses. With Marchiori's help, they've connected those monitors to computers and radio equipment transmitting real-time data back to campus. That data will tell them how the underground barrier reacts to seasonal cycles in temperature and moisture, the pressures in the wall and other conditions over time.
The researchers are also intentionally introducing flaws into a section of the wall — adding large boulders and pockets of sand, for example — to test the effectiveness of a new method for detecting those defects using electrodes in the wall.
"As a geophysicist, I am hoping to provide a technique that can be repeated on other slurry walls to assess the size and location of defects that would undermine the effectiveness of the wall," said Jacob.
"The idea is that when we build these walls in the field, we want to know that we built them properly," added Malusis. "There should be ways to verify the presence or absence of major defects, and currently there's nothing available to do that sort of quality-assurance survey."
The wall is located just across the Susquehanna River from campus between Montandon Marsh and a gravel mine owned by Central Builders Supply of Lewisburg, which granted Bucknell rights to access the property and construct the wall.
In addition to potentially affecting construction standards worldwide, the site will provide rich opportunities for student research. In addition to Alves, five Bucknell undergraduates and one graduate student worked on the wall project this summer. Some said it's providing practical lessons difficult to attain in a classroom setting, including how to work with practitioners from a variety of backgrounds.
"There are various fields involved in this project — such as geology, engineering and computer science — so we have gained experience in how to work with different departments and fields," said Amy Mucelli '17, a geology major who is collecting and analyzing geophysical data with Jacob this summer. "I have also gained a lot of field experience and a clearer insight into the industry that I wouldn't get in the classroom. I have a better understanding of what fieldwork is actually like, which has helped me determine my future plans in the geology field."
"Working in the field, you learn a wide range of things you don't think about in the classroom — from determining how much water to bring to learning how an excavator is operated," added Lindsey Aborn '17, an environmental geology major who is also working with Jacob. "This research project has allowed me to have hands-on learning experiences that have taught me how to problem-solve."