- 學位論文
A Study on Seismic Resistance Evaluation Methods for Embankments with Consideration of Rainfall Effect
A Study on Seismic Resistance Evaluation Methods for Embankments with Consideration of Rainfall Effect
摘要
根據最近的研究降雨會影響土堤的耐震能力，但是至今仍沒有一個 有效的考慮降雨影響的耐震評估方法。此外，剪力模數受到降雨的 影響為何也仍不清楚。為了避免降雨與地震對土堤造成的災害，前 述的兩個問題必須加以處理的。 本研究透過與動態有限元素法的分析結果的比對，檢視了一個基於 能以簡單的模式和少數的參數進行土堤穩定分析的 Newmark 方法而 發展出來的可以考慮降雨影響的方法。另一方面，也利用動態有限 元素法探討了剪力模數的改變對土堤耐震能力的影響。降雨的影響 係以吸力(suction)的改變來表示，而剪力模數因為降雨的改變則是 使用了可以考慮吸力影響的剪力模數模式。 與動態有限元素法的分析結果比較後發現，使用 Newmark 法考慮降 雨的影響，當輸入的地震之最大加速度較小時，會低估土堤的殘餘 位移；但當輸入的地震之最大加速度超過某個數值時，則會高估土 堤之殘餘位移。根據此一結果，本研究針對 Newmark 法提出了一個 修正係數與最大加速度的雙線性關係式。此外，本研究也發現剪力 模數的改變對於土堤的受震殘餘位移的影響很小，因此在土堤的耐 震評估中可以忽略其變化的影響。
並列摘要
According to the recent studies, it was shown that the rainfall would reduce the seismic resistance of embankment. However, there is no general seismic resistance evaluation method which can consider the effect of rainfall yet. In addition, the effect of shear modulus variation due to rainfall is not clarified yet. In order to prevent the complex disaster of rainfall and earthquake, these two problems should be addressed. In this study, a method to consider the effect of rainfall based on Newmark method was examined, which can conduct the analysis with simple model and a few parameters. The applicability of the method was also examined comparing with the result of dynamic FEM analyses. In addition, the effect of the change of shear modulus on the seismic resistance of embankment was also examined by using dynamic FEM analyses. The effect of rainfall was considered as a change of suction. The change of suction was taken into account in the shear modulus model. By comparing with the results of FEM analyses, it was found that for Newmark method with the consideration of rainfall, the residual displacement is underestimated the when the maximum input acceleration is small and overestimated when the maximum input acceleration exceeds certain value. Thus, the correction coefficients for the results of Newmark method are proposed based on the comparison of analysis results from Newmark method and FEM method and the relationship between maximum input acceleration and correction coefficient is bilinear. It is also found that the effect of shear modulus variation on seismic displacement is small enough to be neglected for the seismic residual displacement evaluation.