500kV地下变电站基坑围护结构抗震影响因素

Analysis on seismic influence factors of underground electric substation foundation pit enclosure structure

以上海世博会500 kV地下变电站基坑围护结构为例,运用三维快速拉格朗日程序FLAC3D进行建模计算,研究了一些对基坑围护结构以及周围土体抗震稳定性有较大影响的因素:基坑周围土体性质、围护结构材料性质、地震波的峰值加速度以及地震波的卓越频率。结果表明:基坑的振动变形受周围土体的约束,土体的性质越好,约束作用越明显,振动变形越小;基坑的存在对周围土体的震动特性影响也很小。基坑围护结构的强度对基坑整体振动变形有影响,但是影响作用不明显;围护结构内力值随围护结构材料强度增大而增大,抵抗破坏的能力同样也随之增强。同一地震波若放大其峰值加速度,则使其能量放大,基坑的振动变形也随之变大,然而其内力值变化不明显。基坑在周围土体的约束下,没有表现出相应的自振特性。所得出的结论可以为类似圆形深基坑抗震设计提供参考。

Based on the 500 kV underground electric substation foundation pit enclosure structure of Shanghai World Expo,a modeling calculation was done with the fast largangian analysis of continua in dimensions（FLAC3D,and some major influence factors on the foundation pit enclosure structure and the seismic stability of the surrounding soil were studied.The factors included four aspects,namly the nature of the surrounding soil of the pit,the properties of the foundation pit enclosure structure,the peak acceleration of the seismic waves and the dominant frequency of the seismic wave.The results show that the vibration of the pit deformation is constrained by the surrounding soil,that the better the nature of the soil,the more obvious the constraints,and the smaller the vibration deformation,that the pit has also little influence on the vibration of the surrounding soil,that the strength of the underground substation has an effect on the vibration deformation of the whole pit,but the influence is not obvious,that the internal force value of the enclosure structure and the ability of damage resistance increase with the material strength of the enclosure structure,that if the seismic wave amplifiee its peak acceleration,its energy will amplify as well as the deformation of the pit,but internal force value has no obvious change,and that under the constraint of the surrounding soil,the pit shows no corresponding natural vibration characteristic.These conclusions may provide reference similar circular foundation pit seismic design.