Effect of Shaking Duration on Foundation Settlement in Liquefiable Soils: 1-g Shake Table Tests

The effects of shaking duration on liquefaction-induced settlements have been studied in the past, but there is a lack of experimental data in the literature. Therefore, a series of moderate scale 1-g shake table experiments are conducted to evaluate the influence of shaking duration with the same input motion in liquefiable soil layers. First, a 1/5 scaled model is prepared based on a large-scale shake table experiment conducted recently at the University of California, San Diego. The scaled model consists of three soil layers with relative densities of 50% for the top crust, 30% for the middle liquefiable, and 85% for the bottom dense layers. Second, a shallow foundation is seated over the crust layer, which consists of unsaturated sandy soil. Third, the models are subjected to harmonic input motions with different shaking durations (i.e., 8, 12, and 15 s). Based on the prototype test, the expected settlement of the foundation was 25 mm; however, the measured settlement was 60 mm. The foundation and free field settlement increased from 7 mm to 157 mm and 3.5 mm to 14 mm when the shaking time was increased from 8 to 15 s.