近远场地震下高陡边坡的动力响应及永久位移分析
Dynamic response and permanent displacement of high-steep slopes under near- and far-field earthquakes
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摘要: 基于软硬互层边坡的有限元模型,研究了边坡在近远场地震作用下的动力响应规律,得出远场地震对边坡动力响应(动力放大系数、最大剪应力和最大主应力)的影响总体比近场地震显著;通过将时程分析法与规范中的拟静力法计算的安全系数进行对比,明确了拟静力法在地震动力稳定性评价中的不足;基于有限元时程分析法计算出的边坡临界加速度代入Newmark滑块位移法公式中,得到了考虑地震近远场特性影响的边坡永久位移,并与弹塑性有限元数值模拟结果进行了对比,得出Newmark法计算结果偏小,且远场地震作用下的永久位移比近场地震作用下分别增大35%(Newmark法)和21%(弹塑性有限元法);最后基于Jibson and Michae 提出的边坡稳定性评价的永久位移量进行了边坡的稳定性评价,得出以永久位移1 cm作为岩质边坡从一个轻度破坏到中度破坏程度的评价临界值较为合理。Abstract: Based on the two-dimensional finite element simulation model of rock slope interbedded by hard and soft layers, the dynamic responses of the slope under near-field and far-field earthquakes are studied. The dynamic responses (dynamic amplification factor, the maximum shear stress and the maximum principal stress) under far-field earthquakes are greater than those under near-field earthquakes. The safety factors of the slope calculated by means of the time history method and the pseudo-static method of Chinese standards are compared, and the pseudo-static method has shortcomings in seismic dynamic stability evaluation. The critical acceleration calculated by the elastic-plastic finite element numerical simulation is substituted in Newmark's sliding block formula, and the permanent displacements of the slope considering the effect of near-field and far-field earthquakes are calculated. The results calculated by use of the Newmark's method are lower. The permanent displacements under far-field earthquakes increase by 26% (Newmark's method) and 29% (elastic-plastic finite element method) compared with those under near field earthquakes. Finally, the stability of slope is evaluated based on the permanent displacements proposed by Jibson and Michae, and the permanent displacement of 1 cm as the critical evaluation value of slope from mild damage to moderate damage is more reasonable.