地下管线地震响应及土体弹性抗力系数研究

Investigation on Elastoplastic Seismic Responses of Underground Pipelines and Soil Elastic Resistant Coefficient

基于土体对地下管线弹性约束的现有设计方法不考虑管土间的塑性滑移,夸大了周围土地对管线的约束程度。研究采用弹性地基梁模型并考虑管土界面上土体剪切破坏或界面摩擦所产生的塑性滑移,发展了地下管线弹塑性地震反应计算方法,推导给出了管体应变的基本计算公式,公式采用滑移系数反映管土间相对滑移所引起的管应变的降低。此外,考虑管线受到行波激励的简谐波作用,推导了土体弹性抗力系数的计算公式,而临界剪应力取为依据土体抗剪强度和摩擦力计算的较小值。通过将简化计算结果与精细有限元分析的对比,验证了本文弹塑性地震反应法和土体弹性抗力系数取值的合理性。

The current design method of buried pipeline is based on elastic restraint of soil to the pipe, which actually overestimates the effect of soil. On the assumption of elastic foundation beam model, a formula for calculating pipe strain under earthquake excitation has been derived with consideration of elastoplastic slippage between soil and pipeline. The slippage factor is used to estimate the decrease in pipe strain due to relational slippage between pipe and soil. Furthermore, approach for estimating the elastic resistance coefficient of the soil is studied considering travelling wave excitation of harmonic wave. The critical shearing stress is taken from the smaller one of soil shear stress and friction force. The simplified analysis method is validated by comparing its resuhs with numerical results from complex FEM model.