During the 1989 Loma Prieta earthquake in California, a bridge on Highway 101 near Watsonville supported by piles in soft soil collapsed, and sand boils erupted through the Oakland Airport runways and Bay Bridge approach. UC Davis researchers are employing a powerful technique to test the earthquake safety of such structural foundations: scale models placed in a centrifuge to simulate gravity forces and then shaken to simulate earthquake acceleration forces. According to Bruce L. Kutter, an associate professor of civil engineering, centrifuge tests can help people understand how structures behave when the ground shakes, as well as how designs can be improved to withstand those forces. In the Loma Prieta examples, the centrifuge revealed some heretofore unreported phenomenon in the earthquake damage process. In another study, motivated by the new Harbor Freeway in Los Angeles, researchers using the centrifuge found that sound walls supported by a new, more economical retaining wall known as "mechanically stabilized earth" is potentially a safe alternative for the concrete retaining walls currently favored. The UC Davis researchers reported their findings at the recent annual meeting of the Transportation Research Board. For general information about centrifuge testing, media should contact Kutter at (916) 752-8099; for information about the retaining wall test, media should contact civil engineering professor Karl Romstad at (916) 752-1755. Tip by Carol Cruzan Morton, News Service, 752-7704.