Damage Analysis of Subgrade Engineering in Wenchuan Earthquake and Recommendations for Improving Seismic Design Code

It is important and imperative to improve the current seismic design codes of railway and highway by applying the near-field data in the Wenchuan earthquake. Through a recent survey in the near-fault area,especially Dujiangyan to Yingxiu section of state route No.213,a third-grade highway built in 2005,the seismic failure types and causes of subgrade engineering in the earthquake,including embankment,shoulder retaining wall and cutting retaining wall,were summarized and analyzed. The primary results involve:from the viewpoint of seismic prevention,the pile-plank retaining wall is optimal,the concrete retaining wall ranks second,and the mortar flagstone retaining wall is the poorest; in the regions with a seismic intensity of 9 to 10 degree,the stability of retaining walls was checked and calculated using the current railway seismic design code. The result shows that the safety factor of anti-sliding stability is basically consistent with the macro-seismic damage,the geotechnical grille reinforcement can improve the seismic capacity of embankment projects effectively. Furthermore,from the extension and renewal aspects,the pushing effect of the Wenchuan earthquake on the development of seismic design code of subgrade engineering was discussed. Finally,it was emphasized especially that the firsthand data from seismic intensity above 9 degree and from new types of subgrade engineering provide a rare condition for filling the gaps in the current code.