汶川地震路基震害分析及对抗震规范改进的启示

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

利用汶川地震的大批近场实震资料,对促进铁路、公路抗震设计规范的发展具有重要的科学意义和应用价值.对汶川地震近场区路基震害进行了调查,主要以2005年竣工的都江堰至映秀的三级公路为例,分析了路堤工程、路肩墙和路堑墙的震害模式.研究表明:在常用支挡工程类型中,桩板式挡墙的抗震性能最优,其次为混凝土挡墙,浆砌片石挡墙最差;按现行铁路抗震设计规范,对汶川地震9～10度烈度区的挡土墙进行了稳定性检算,抗滑动稳定安全系数的计算结果与宏观震害情况基本一致;土工格栅加固措施可有效地提高路堤工程的抗震能力.此外,从对现行规范技术框架进行延展和更新2个层面,论述了汶川地震对路基工程抗震设计规范发展的推动作用,并特别指出,汶川地震9度以上近场地震资料以及高等级公路中新型支挡工程、路堤加固工程的实震资料,提供了填补现行规范空白的罕有条件.

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-fauh 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.