UB to begin geotechnical collaboration with Tongji University

Geotechnical engineers at UB and Tongji University will employ each university’s unique lab equipment and experience in a joint-research project exploring liquefaction in transitional soils.

Anthony Tessari, assistant professor in the Department of Civil, Structural and Environmental Engineering, is the lead UB faculty member on the project; Xiaoqiang Gu, assistant professor of geotechnical engineering at Tongji — the top civil engineering school in the world, according to the Academic Ranking of World University (AWRU), or Shanghai Rankings — will lead the project for the Chinese university. Tessari worked with department faculty members Andrew Whittaker, SUNY Distinguished Professor, and Teng Wu, assistant professor, to secure the collaboration, which will begin later this year.

The researchers and some students will work together on the project exploring liquefaction in transitional soils. Liquefaction in soils “is essentially where a soil turns into a liquid,” Tessari explains. “Water pressure is so high inside the soil and is actually greater than the actual self-weight of soil. It forces particles to separate, and turns it into quicksand.

“We have a good understanding of how it works in pure sands and gravels,” he says. “We’re trying to figure out what triggers liquefaction in transitional soils, like silty sands.”

Transitional soils, often referred to as silt, have a consistency between sand and clay, and they do not always liquify. Tessari and Gu will try to determine, from a physics standpoint, why these soils liquify. Their findings could provide insight on how transitional soils can affect the seismic-resilience rating system.

The unique equipment in each university’s lab makes this an ideal collaboration, Tessari says.

“Behavior of soil in the field is really important. In the middle of the field, you have nothing; boundaries are almost infinite,” he says. “Normally, we would take a tiny sample and bring it into the lab. You can control things and reproduce them at a small scale, but there are disadvantages. It’s a very small sample and the boundary conditions are all wrong.”

To begin to fill in the gap between what happens in the field and the lab, UB-Tongji collaborators will use the centrifuge at Tongji, which can build a sample at 1/50 scale. The device can apply 50gs of force to the sample and technically create some of the same conditions found in the field. But this experiment, too, has limitations, Tessari says.

“It’s not really the same because everything scales at 1/50; height over 50. It would be fine, but the water pressure dissipation is a function of area. While everything else scales by 50, area scales by 50-squared. That’s where we come in with our big laminar box,” he says.

UB’s laminar box has the capabilities to create an area equivalent to that in the field.

“Each one of these techniques has an advantage and a disadvantage,” Tessari says. “When you put them all together, they cancel out those disadvantages and we end up with something that’s really meaningful.

“That’s the idea: We’re complimenting each other’s strengths in a way that creates an output greater than the sum of individual components,” he says. “International collaboration is always mutually beneficial.”