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以青藏铁路工程抗震设计与加固为应用背景,采用地震反应分析的二维动力有限元法,开展青藏铁路冻土场地-路基的地震动力反应数值分析,给出了冻土场地-路基最大水平加速度、最大竖向加速度、最大动竖向正应力、最大动水平正应力、最大动剪切应力随地层深度的变化规律。研究表明:冻土层厚度对场地-路基地震动力反应有重要影响。路基顶部,冻土场地的最大竖向加速度远大于非冻土场地的最大竖向加速度,而冻土场地的最大水平加速度小于非冻土场地的最大水平加速度。冻土场地较非冻土场地动应力的峰值基本偏大且频率高,最大动竖向正应力随深度增大呈近似线性增大、而最大动水平正应力和最大动剪应力在冻土层与非冻土层分界附近则呈剧烈波动变化,与非冻土场地路基动应力反应明显不同。据此,指出了冻土场地路基在地震作用下的危险点所在位置。
Taking the seismic design and reinforcement of the Qinghai-Tibet Railway as the application background, the numerical analysis of the dynamic response of the Qinghai-Tibet Railway permafrost site to the subgrade using the two-dimensional dynamic finite element method of seismic response analysis is given. The maximum horizontal acceleration of the permafrost zone , The maximum vertical acceleration, the maximum vertical and vertical normal stress, the maximum dynamic normal stress and the maximum dynamic shear stress with the formation depth. The results show that the thickness of frozen soil layer has an important influence on the site-subgrade earthquake dynamic response. The maximum vertical acceleration at the top of subgrade and permafrost is far greater than the maximum vertical acceleration at non-permafrost sites, while the maximum horizontal acceleration at permafrost sites is less than the maximum horizontal acceleration at non-permafrost sites. The peak value of dynamic stress in the permafrost field is basically larger and the frequency is higher than that in the non-permafrost field. The maximum vertical dynamic stress increases linearly with depth, while the maximum dynamic normal stress and the maximum dynamic shear stress in the frozen soil layer Compared with the non-permafrost boundary, there is a sharp fluctuation, which is obviously different from the dynamic stress response in the subgrade of non-permafrost. Based on this, the dangerous point of permafrost embankment under earthquake is pointed out.