A civil engineer unearths new possibilities for growth

Author: Gina Vozenilek
Professor Antonio Bobet is having deep thoughts about research. Deep underground, that is.

His research interests—engineering geology, underground construction, and rock mechanics—have him delving below the surface of things. While scientists in other fields are pushing the innovation envelope upward, outward, even skyward, Bobet, professor of civil engineering, sees great potential for new engineering discovery and application right below his feet.

One of his most exciting projects is a literal gold mine of opportunity. The Homestake Mine in Lead, South Dakota, which before its closing in 2002 was the oldest, largest, and deepest gold mine in the Western Hemisphere, will
be the site of a major new research center. Certain to stimulate a new rush of scientific discovery, the National Science Foundation is funding the creation of a Deep Underground Science and Engineering Laboratory (DUSEL).

When completed, DUSEL will give scientists access to unique environmental conditions. The depth of DUSEL (its deepest rooms will be at almost 8,000 feet) will, for example, allow astrophysicists to conduct neutrino experimentation insulated from cosmic radiation. Microbiologists will be able to study how bacteria survive and reproduce at extreme depth. Other specialists will study hydrology, physics, and geology. But none of this science will be conducted without innovations by engineers like Bobet. “We are enablers,” he says proudly. “Infrastructure is needed to make DUSEL possible.”

Building DUSEL will push the limits of what is known about the stability of underground structures. Massive, extremely sensitive instrumentation will be housed in DUSEL, and the structure will have to stand up to unprecedented loads. The project also will require civil engineers to explore and define new excavation techniques. “We will come up with new paradigms and push know-how to points we have not been before,” says Bobet. And the knowledge gained will transfer usefully to other commercial construction projects.

Bobet believes in the need to find “different means of solving new problems.” Some of these newer challenges stem from the fact that we are living in a so-called “built” society in which the structures of our cities, roads, bridges, and
utilities are already in place. As building codes get progressively more exacting, old structures need upgrading, and that can cost a pretty penny.

With an interdisciplinary team of scientists, including civil engineering faculty Vincent Drnevich, professor, and Maria Caterina Santagata, associate professor, and Cliff Johnston, Purdue professor of agronomy, Bobet has studied liquefaction, in which soil behaves as a fluid under seismic loading. This action can cause serious distortion to structures like bridges and can have devastating consequences in an earthquake. Bobet’s approach is not to focus on strengthening the bridge. “We have a different way of looking at the engineering,” he explains. “We want to fix the soil.”

Others have tried to strengthen “loose” soils by “densifying” them. But Bobet has gone beyond this idea and turned his attention to the pore space between the soil particles. He has successfully tested a way to “engineer the pore fluid” by using bentonite, a clay nanoparticle. Because bentonite particles are electrically charged, their interaction can be engineered. Bobet’s team has devised the means to decrease the initial viscosity of the bentonite
slurry such that it can permeate into the pore space of the soil; with time the process is reversible and the viscosity of the pore fluid increases, thereby stabilizing the soil. His concept provides a non-invasive—and therefore cost-effective and financially competitive—way of reinforcing bridge foundations located in liquefiable soils around the globe. “I can see this as an innovation with which we will open new doors,” says Bobet. 

Bobet relishes his role as an innovator, both in breaking new ground and in refining existing knowledge. “The U.S. has always been able to move forward and have impact, to push technology further,” Bobet says.

“We still need to keep working on well-established principles,” Bobet observes, “but we should also be working on leaps and jumps forward to another magnitude of progress.”