不同形状三维凹陷地形场地对地震动影响比较分析  

Comparison and analysis of the influence of different shapes of 3D concave topographies on site ground motion

作　　者：李小军[1,2] 任朋亮 王玉石 李再先 钟康明 董青 LI Xiao-jun;REN Peng-liang;WANG Yu-shi;LI Zai-xian;ZHONG Kang-ming;DONG Qing(Key Laboratory of the Ministry of Education for Urban and Engineering Safety and Disaster Reduction,Beijing University of Technology,Beijing 100124,China;Institute of Civil Engineering,Institute of Disaster Prevention,Sanhe,Hebei 065201,China)

机构地区：[1]北京工业大学城市与工程安全减灾教育部重点实验室,北京100124 [2]防灾科技学院土木工程学院,河北三河065201

出　　处：《岩土力学》2023年第11期3327-3338,共12页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.52192675);高等学校学科创新引智计划(No.D21001)。

摘　　要：采用有限元离散模型、黏弹性人工边界和中心差分积分格式相结合的方法,开展三维凹陷地形场地地震反应计算,分析了P波和SV波入射下均匀弹性半空间三维棱锥形凹陷、半球凹陷和棱柱形凹陷地形场地对场地地震动的影响特征与差异。研究表明:(1)不同形状的凹陷地形对场地地震动的影响差异显著,即棱柱凹陷地形>半球凹陷地形>棱锥凹陷地形,但不同形状凹陷地形影响之间的差异更多地表现在中频范围内;(2)凹陷地形对地震波具有复杂的散射作用,无论是垂直入射的P波还是垂直入射的SV波(仅竖向或水平向地震动输入),在凹陷区及附近均能产生两个方向很显著的地震动,且在SV波垂直入射下的凹陷散射更为强烈,其产生的竖向地震动幅值甚至超过水平向的;(3)凹陷地形可能会产生地震动的地形边缘效应,棱柱形凹陷边缘处地震动被显著地放大,而半球凹陷地形、棱锥形凹陷地形中这一效应相对较弱。研究揭示了凹陷边缘陡峭程度对场地地震动有显著的影响,而且凹陷地形边缘效应可能存在并与凹陷边缘陡峭程度密切相关。这一研究结果对实际工程问题分析给出了重要提示:建立凹陷地形的简化分析模型时需要特别关注凹陷边缘部位的合理处理。研究结果可应用于山区工程建设,特别是桥梁和水坝建设,为其抗震设防考虑不同凹陷形状地形对场地地震动影响的特征及差异,特别是可能出现的地形边缘效应提供参考。The seismic responses of three-dimensional(3D)concave topography sites were calculated by the combination method of finite element discrete model,the viscoelastic artificial boundary and the central difference integral formula,and the characteristics and differences of the influence of pyramid-shaped,hemisphere-shaped and prism-shaped concave topographies in homogeneous elastic half space on site ground motion were analyzed under the vertical incidence of P wave and SV waves.(1)The influence of different shapes of concave topographies on site ground motion is significantly different,namely,the prism-shaped concave topography>the hemisphere-shaped concave topography>the pyramid-shaped concave topography,but the differences between the different concave topographies are more manifested in the medium frequency range.(2)Concave topographies have a complex scattering effects on seismic waves.Whether it is vertically incident P wave or vertically incident SV wave(only vertical or horizontal seismic motion input),it can produce significant ground motions in both directions in and near the sag area,and while SV wave is vertically incident,the wave scattering of concave topography is more intense,and furthermore the amplitude of ground motion in vertical direction generated by SV wave is even greater than that in horizontal direction.(3)The concave topography may cause the topographical edge effect of ground motion,and the ground motion at the edge of prism-shaped concave is significantly amplified,while this effect is relatively weak in the pyramid-shaped and hemisphere-shaped concave topographies.The study reveals that the steep degree of the concave edge has a significant impact on site ground motion,and that the edge effect of concave topography may exist and is closely related to the steep degree of the concave edge.This research result gives an important hint for the analysis of practical engineering problems,that is,the rational treatment of concave edge parts should be paid special attention to when establishing a

关 键 词：场地地震动 凹陷地形 地形影响 黏弹性边界 地形边缘效应 

分 类 号：TU475[建筑科学—结构工程]