土钉支护边坡动力模型的建立及地震响应分析

参照上部结构抗震设计的方法,对土钉支护边坡的抗震设计提出了3个水准的抗震设防要求和两阶段设计法。综合考虑输入地震波的特性、边坡土体特性、坡高因素,以及土体边坡在水平地震激励下,其位移响应主要为剪切型变形,建立了土钉支护边坡地震动力简化模型。该模型将同一水平层不稳定土体、稳定土体在水平地震作用下运动趋势假想为同步,两者之间相互作用很小,因此,取不稳定土体和面板为研究对象。由于面板很柔,其运动随着土体的运动而变化,其刚度只考虑剪切刚度,将土钉处理成弹性支座,建立了土钉支护边坡振动方程,求解了在简谐地震作用下土钉支护边坡动力响应的解析解,通过该模型可以得到滑移面附近土钉轴力动力响应和土钉支护边坡的弹性动位移响应。最后,结合案例进行了分析,比较了按此分析方法与用ADINA按弹性有限元方法计算的结果,两者吻合较好。故这种方法可用于土钉支护边坡的第1阶段的抗震分析与设计。

Dynamic calculation model and seismic response for slope protected by soil nailing under earthquake

Corresponding to design method of highrise building aseismic design, the request of three levels aseismic fortification design and the design way of two stages are proposed for the slope protected by soil nailing. Considering seismic excitation property, soil property and slope height, occurring shear displacement under horizontal excitation, a simplified dynamic calculation model of soil nailing protected structures for the slope is proposed. Based on the hypothesis that the lateral displacement of the stability soil and instability soil is nearly in phase and the lateral interaction between them is ignored under horizontal excitation, the instability soil and the facing are treated as study object. Because the facing is flexible, its lateral displacement depends on the lateral displacement of instability soil. The soil nailing is served as the elastic supports. Under the condition of horizontal earthquake excitation the equation of vibration is established in accordance with being mentioned ahead; the analytical solutions are obtained for simple harmonic vibration. The soil nailing axial force response in the neighborhood of failure surface and elastic lateral displacement history can be obtained by this method. The method is applied to a case record for illustration of its capability; in order to verify the method 3-D nonlinear FEM (ADINA) is used to analyze the seismic performance of this case; the comparison of results, using the proposed approach and FEM shows good agreement. This method can be used the first stage aseismic fortification design and analysis of the slope protected by soil nailing.