土–地铁动力相互作用体系侧向变形特征研究

Characteristics of lateral deformation of soil-subway dynamic interaction system

针对现有地下结构抗震分析方法用于地铁大型地下结构的可行性研究明显不足问题,根据中国抗震规范的相关规定设计了常见的3种场地类别,考虑输入地震动特性及其强度,通过84种有限元计算工况,分析了土–地铁地下结构非线性动力相互作用体系的侧向变形特征。结果表明,在Ⅱ、Ⅲ、Ⅳ3个场地类别条件下输入加速度峰值较大时(0.3g和0.4g),或者场地类别为Ⅳ类时即使输入很小地震动峰值加速度时,土与结构相互作用系数均小于1,即大型地铁地下结构侧向土体总是"推着"地下结构产生最大相对变形,此时地铁地下结构周围土层的大变形将对地下结构抗震造成不利的影响。反之,将会出现地铁地下车站结构侧向最大变形大于等代土体单元的侧向变形,即地下结构的动力变形将受到周围土层的约束作用,此时将对地下结构的抗震起到有利作用。同时,也给出了场地类别和输入地震动特性对土–地铁地下结构相互作用系数的影响规律。

With regard to the insufficient researches on the reliability of the existing seismic analysis methods for underground structures for the seismic design of large-scale underground structures, three site classifications are designed according to the relevant seismic design codes, and the characteristics of seismic deformation of the interaction system are analyzed under 84 conditions by using the finite element method. The results show that when the peak acceleration of input earthquake wave is larger than 0.2g with any kind of site classification or when the site classification is Ⅳ under very small peak acceleration, the soil-structure interaction coefficients are all smaller than one, which means that the lateral soils with large deformation may push the underground structure to be deformed maximally. In other word, the large deformation of the surrounding soil foundation is unfavourable to the seismic performance of the large underground structures. On the contrary, the maximal deformation of the underground structures should be constrained by the surrounding soils, which is favourable to the seismic performance of the underground structures. Meanwhile, the effect laws of the site classification and the properties of input ground motion on the seismic deformation of the large underground structures are also analyzed.