凸出部放大效应在桥址高边坡地震稳定性评价中的应用探讨  

Discussion on the application of amplification effect of protrusions in seismic stability evaluation of high slopes at bridge sites

作　　者：秦辉 汤华[1] 尹小涛[1] 程谞 汤盛平 QIN Hui;TANG Hua;YIN Xiao-tao;CHENG Xu;TANG Sheng-ping(State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071 [2]中国科学院大学,北京100049

出　　处：《岩土力学》2024年第11期3435-3446,共12页Rock and Soil Mechanics

基　　金：云南省重点研发计划(No.202303AA080010)。

摘　　要：深切峡谷区桥址高边坡凸出部具有三面临空和多面卸荷的典型地质地貌特征,研究边坡凸出部地震地形放大效应对桥址边坡安全控制尤为重要。依托特大桥桥址高边坡,研究了地震作用下边坡凸出部放大效应和变形破坏机制,优化了墩台位置。研究结果表明:(1)现场调查和数值模拟综合印证了边坡凸出部山顶碎屑流和主墩下部危岩体发育,受历史震害强。加速度随坡高呈现非线性放大的规律,开挖加剧了挖方区域加速度放大效应。凸出部(坡脊)坡腰和坡顶位置放大系数最大,加速度放大系数M_(PGA)最大可达3.2。(2)坡脊高频部分(5~12 Hz)的加速度傅里叶谱幅值普遍比坡谷大,开挖导致墩台上(下)边坡的傅里叶幅值的峰值减小在(增大)。开挖位置附近的傅里叶谱幅值的峰值均随峰值加速度的增加呈现先增大后减小的趋势。(3)《建筑抗震设计规范》中限制了最大坡高和放大系数极值,可能造成高边坡凸出部的动力放大效应被低估,使得凸出部地震稳定性评价结果偏危险。(4)为保证桥址边坡的地震稳定性,采用文中所述方法优化墩台外侧距坡面的距离为22~26 m。研究成果可为有凸出部的高边坡地震稳定性评价和墩台位置优化设计提供指导。The protruding part of the high slope at the bridge site in the deep canyon area has typical geological and geomorphic characteristics of three faces exposed to the air and multiple unloading faces.Studying the seismic terrain amplification effect of the protruding slope is crucial for ensuring the safety and stability of the bridge site.This study investigated the seismic amplification effects and deformation mechanisms of the slope’s protruding parts at the large bridge site and optimized the positioning of piers and abutments.The research results indicate:(1)Field investigation and numerical simulation comprehensively confirm the development of debris flow at the top of the slope bulge and the instability of the rock mass at the lower part of the main pier.These conditions have been significantly affected by historical earthquakes.The acceleration exhibits a nonlinear amplification pattern that is influenced by the slope height,and excavation exacerbates the acceleration amplification effect in the excavation area.The maximum amplification factor is at the waist and top of the bulge(ridge),and the maximum acceleration amplification factor(M_(PGA))reaching 3.2.(2)The acceleration Fourier spectrum amplitude of the high-frequency part of the slope ridge(5-12 Hz)generally exceeds that of the slope valley.Excavation leads to a decrease in the peak value of the Fourier amplitude of the upper slope of the pier and abutment,while the lower slope experiences an increase.The peak value of the Fourier spectrum amplitude near the excavation location initially increases and then decreases with the increase of peak acceleration.(3)The maximum slope height and the extreme value of amplification factor are limited in the seismic design code for buildings,potentially leading to an underestimation of the dynamic amplification effect of the bulge and resulting in a more hazardous seismic stability evaluation of the bulge.(4)To ensure the seismic stability of the bridge site slope,the optimal distance between the outer edge of

关 键 词：桥址边坡 凸出部 地震放大效应 频谱特性 墩台位置优化 

分 类 号：TU445[建筑科学—岩土工程]