Abstract: Seismic safety of high fill subgrade presents a difficult design problem, constituting one of the greatest challenges in the development of highway in West China. To study the seismic damage and dynamic characteristics of fill subgrade, firstly the fill subgrade seismic damage of Wenchuan Earthquake is investigated finding out that the main seismic damage type of fill subgrade is rip of upside and bulge of downside. The seismic response and damage of fill subgrade was studied through a shaking table test. In order to model the main factors that influence the seismic response, the model system included the dynamic interactions between the subgrade and retaining wall, construction progress, boundary conditions, etc. The model is made of red beds and quartz sand, meets the requirement of similitude. Results show that the subgrade slope has amplification effort to input seismic waves; and the effect becomes extremely prominent around the crest of the subgrade. The study also shows that the top of the retaining wall and the crest of the subgrade are the vulnerable parts of subgrade and cracks normally appear near these parts under seismic motion. The dynamic characteristics of the subgrade as well as its weak portions during earthquakes are discussed, so as to provide valuable references for seismic appraisal of subgrade.

Key words: fill subgrade, shaking table, seismic response, seismic safety