Experts use Miami’s soils for earthquake research

MIAMI, Okla. — Northeast Oklahoma isn’t known for earthquakes, but earthquake-related engineering research has come to town.

Researchers were in Miami last week to study how foundations that support structures such as bridges behave in soft clay during an earthquake, said K.K. “Muralee” Muraleetharan, a professor in the University of Oklahoma’s School of Civil Engineering and Environmental Science and the project’s principal investigator.

A section of land beneath the Oklahoma Highway 125 bridge over the Neosho River and across from Riverview Park was chosen because of its soil makeup, Muraleetharan said. He was directed to the site after asking the Oklahoma Department of Transportation, which keeps soil data, about land in the state that had roughly 15 to 16 feet of soft clay with a dense, sandy gravel beneath it.

Similar soil types are found in earthquake-prone places such as San Francisco, Calif., and in Missouri and Arkansas, portions of which lie in the New Madrid Seismic Zone.

“When you have a bridge in soft clay, when an earthquake comes, it’s going to move a lot,” Muraleetharan said. “(The Miami soil) turned out to be a perfect site.”

Researchers will install large, steel tubes or reinforced concrete cylinders about 21 feet deep into the ground in both clay soil and soil in which the clay has been mixed with cement, Muraleetharan said. The piles, which are typically cast into the ground before a structure is built, will be subjected to earthquake-like conditions using a portable shaker and will be studied to see how they hold up.

Muraleetharan said that by testing the cement-clay mixture, he hopes to study whether such a combination would be cost-effective and safe for large structures.

Muraleetharan and his crew were in Miami last week installing the piles. They plan to return sometime next month to perform their earthquake simulation.

The experiment in Miami is one part of a multiyear earthquake research project that began in October 2008. The team already has conducted tests in California with a centrifuge, in which small models of structures were subjected to earthquake-like increased gravitational acceleration.

City Manager Huey Long said last week that it is “a big deal” for Miami to host Muraleetharan and his team, whose research he said will affect communities worldwide.

But Miami residents should not be rattled about earthquake research in their own backyard, Muraleetharan said.