Discussions on Two Key Technical Problems for Seismic Design of Retaining Structures
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摘要: 对"5·12"汶川特大地震四川灾区约3000km公路和铁路支挡结构的破坏类型、破坏模式进行了全面调查.根据调查结果,对支挡结构的性能设计和挡土墙墙背地震土压力作用点位置这2个问题进行了讨论,提出支挡结构的抗震设计应考虑墙体位移对支挡结构抗震设计三级设防的要求.对支挡结构的抗震性能可做如下规定:性能要求1:与多遇地震水平一致,位移指数在1.0%以内;性能要求2:与设计地震水平一致,位移指数在3.5%以内;性能要求3:与罕遇地震水平一致,位移指数在6.0%以内.研究表明,地震作用下墙背土压力作用点距挡土墙底的高度为0.45~0.63倍墙高,作用点位置与墙高和墙后土体的性质有关.Abstract: Detailed investigation was carried out on the failure mode of retaining structures caused by the Wenchuan earthquake along highways and railways summing up to 3 000 km in length in Sichuan. From the investigation results,two key technical problems,performance-based design method of retaining structures and the action point of seismic earth pressure,were discussed. It is believed that earthquake-resistant design of retaining structures should consider the requirement of the displacement of retaining walls on three seismic design levels. Performances of retaining structures associated with the three seismic levels may be defined as follows:the performance requirement for the three seismic design levels is that the displacement index is less than 1.0% for a small earthquake level,below 3.5% for a moderate earthquake level and less than 6.0% for a large earthquake level. The research shows that the action point of resultant seismic earth pressure is at the location of 0.45 to 0.63 times wall height above the foot of retaining walls,and the location of the action point is impacted by the wall height and backfill properties.
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