August 2, 2013
University of Texas research will help cities rebuild after quakes
T-Rex and University of Texas, Austin, researchers conduct field testing at the site of an in-situ soil liquefaction test in Christchurch, New Zealand. The wooden stake marks the location of the test. From left are Julia Roberts, UT graduate student; Robert Kent, NEES@UTexas IT manager; Andrew Valentine, NEES@UTexas shaker operator; and Sungmoon Hwang, UT graduate student. (University of Texas, Austin/NEES photo).
Researchers from the University of Texas at Austin are conducting a study that will help a city rebuild after a string of earthquakes, thanks to a boost from the U.S. National Science Foundation and the government of New Zealand.
The knowledge gained could one day help set building codes in earthquake-prone areas in the United States and abroad.
This summer, two faculty members and two graduate students from the Cockrell School of Engineering are conducting field research in Christchurch, the second largest city in New Zealand, where six powerful earthquakes hit in 2011.
Since then, as many as 7,500 homes have been abandoned because of earthquake damage, and about 2,400 out of 3,000 structures in the central business district have been demolished. During the earthquakes, different parts of Christchurch were affected by liquefaction - the process by which water-saturated sediments, or soil, temporarily become liquid-like.
The government of New Zealand is supporting the earthquake-related research with $2.2 million to fund the construction of 16 ground improvement sites in different soils around Christchurch. The government is providing UT Austin researchers free access to the testing sites. In addition to New Zealand's support, the U.S. National Science Foundation (NSF) is funding the project through a grant worth approximately $200,000.
The research, which will be discussed at the NEES Quake Summit 2013 next week in Reno, Nev., will help address a critical problem facing Christchurch and the Canterbury region: rebuilding on land that remains at risk of liquefaction in future earthquakes.
The research team, which arrived in New Zealand in mid-June, expects to complete the field project this summer.
"This liquefaction field work has never been done before and represents critical, basic research as well as important practical knowledge for Christchurch to move forward in its developments," said Kenneth Stokoe, principal investigator on the project and professor in the Department of Civil, Architectural and Environmental Engineering. "The study will impact the future Christchurch society through the development of more robust seismic designs of residential structures for more than 15,000 homes."
Currently, little information exists on the types of ground improvement methods that can be used to improve the resiliency of residential structures and low-rise buildings in future earthquakes. Researchers are conducting full-scale field tests of shallow ground improvement methods, evaluating which soil improvements will perform best in future earthquakes.
The grant, which is part of NSF's Rapid Response Research (RAPID) program, will be used to fund expenses and salaries associated with the project, which is called "RAPID: Field Investigation of Shallow Ground Improvement Methods for Inhibiting Liquefaction Triggering."
The project's goal is to determine whether various ground improvement methods help inhibit liquefaction, and which of the methods tested would be most cost-effective. Civil engineering assistant professor Brady Cox is also a lead on the project.
The liquefaction testing is being conducted using a large mobile shaker truck, called T-Rex, which is operated by NEES@UTexas at UT Austin.
The 64,000-pound T-Rex is used to simulate a wide range of earthquake shaking levels. The shaker truck was transported to New Zealand earlier this year for use in another NSF-funded (NEES) project involving deep seismic profiling.
The project in Christchurch is one of many with The George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES), a national network and simulation resource, funded by the U.S. National Science Foundation and led by Purdue University.
NEES has 14 such sites across the country. NEES at UT Austin, led by civil engineering professors Stokoe and Cox, is the only site with truck-mounted mobile shakers that can be used to simulate earthquake waves. UT Austin's T-Rex is the only known operating tri-axial vibroseis truck in the country.
Stokoe and his team have worked closely with their colleagues from the University of Canterbury and geotechnical engineer Sjoerd van Ballegooy of Tonkin & Taylor Ltd. - who have been working hard to help Christchurch recover from the aftermath of the earthquakes.
This research will have applications for earthquake-prone cities in the United States, as well as numerous other parts of the world. The first phase of testing should be complete by August.
"We will work for another year to dig deeper into the basic research findings," Stokoe said. "This stage mainly determines which ground improvement methods are best suited for Christchurch and will allow them to move forward in rebuilding a resilient city."
Members of NEES are gathering next week at the University of Nevada, Reno for Quake Summit 2013, a scientific meeting highlighting research on mitigating the impact of devastating earthquakes and tsunamis. Titled "Earthquake & Multi-Hazards Resilience: Progress and Challenges," the annual summit of the 14-site NEES, is from Aug. 6-8.
Since Oct. 1, 2009, the NEES operations and cyberinfrastructure headquarters has been located at Purdue's Discovery Park, the result of the NSF cooperative agreement #CMMI-0927178.
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Related news release: http://www.engr.utexas.edu/features/7536-brady-cox-trex-shaker-truck
Related website: NEES News