Published May 10, 2018
Geotechnical engineers at UB and Tongji University will utilize each other’s unique lab equipment and experience in a joint-research project, to begin later this year. Tongji University is the top civil engineering school in the world, according to the Academic Ranking of World University (AWRU), or Shanghai Rankings.
Assistant professor Anthony Tessari is the lead UB faculty member on the project, and will work with his counterpart in Tongji, professor Xiaoqiang Gu. The pair of researchers and some students will work together to explore liquefaction in transitional soils. Tessari worked with department faculty members Andrew Whittaker and Teng Wu to secure the collaboration.
“This is essentially where a soil turns into a liquid. 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,” Tessari says, “We have a good understanding of how it works in pure sands and gravels. 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. They do not always liquify. Tessari and Gu will try and determine why these soils liquify from a physics standpoint. Their findings could provide insight on how transitional soils can affect the seismic resilience rating system. The equipment in each university’s labs make this an ideal collaboration.
“Behavior of soil in the field is really important. In the middle of the field, you have nothing; boundaries are almost infinite,” Tessari 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 can use the centrifuge located at Tongji University. Tongji’s centrifuge can build a sample at 1/50th scale. The device can apply 50gs of force to the sample, and technically create some of the same conditions found in the field. This experiment, too, has limitations, according to Tessari.
“It’s not really the same because everything scales at 1/50th; 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.
The 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 creates an output greater than the sum of individual components. International collaboration is always mutually beneficial.”