Ground motion characteristics analysis of sedimentary valley site with SH wave oblique incidence based on IBIEM
SONG Zhiqiang1, ZHAO Leichao1, WANG Fei1, ZHI Bingcheng2, LIU Yunhe1
1.State Key Laboratory of Eco-hydraulics in Northwest Arid Region ,Xi’an University of Technology, Xi’an 710048, China；
2.Sichuan Water Resources And Hydroelectric Investigation & Design Institute Co., Ltd., China
摘要应用任意地形河谷沉积层散射波源的格林函数公式，基于间接边界积分方程法（indirect boundary integral equation method，IBIEM），分析了SH波斜入射下梯形沉积河谷场地地震动特性和分布规律，研究了地震波斜入射角度、斜坡坡度、介质阻抗比对地震动特性及非一致分布规律的影响机制，深入分析了河谷散射效应对地基截断边界地震动场的影响规律。结果表明：斜入射使得河谷表面峰值位移的放大效应和非一致效应显著增强，最大峰值位移达入射地震动峰值的5倍以上；当河谷底宽较大时，沉积河谷的边缘效应明显；当底宽较小时，沉积河谷的聚焦效应明显，表面最大值出现在河谷中心处；斜坡坡度对楔形体内、外表面附近地表处的地震反应影响强烈，该现象可以由地表折射波干涉区域与斜坡坡度、入射角、波速的确定函数关系得到解释；随着阻抗比的增大，位移幅值放大越来越显著；斜入射时，对于刚度越小的软弱沉积层对地震波传播起到屏障作用；无论是空心河谷还是沉积河谷，散射效应对边界处地震动场影响都较为明显，相对于平坦基岩自由场，底边界、右边界误差最大可达30.8%、54.8%，应将考虑散射效应的总场作为输入。
Abstract：By using the Green's function formula of scattered wave sources in river valleys with arbitrary topography, and based on the indirect boundary integral equation method (IBIEM), the ground motion characteristics and distribution of trapezoidal sedimentary valley sites under oblique incidence of SH waves are analyzed, and the influence mechanisms of seismic wave oblique incident angle, slope slope and medium impedance ratio on ground motion characteristics and non-uniform distribution are studied. In this paper, the influence of valley scattering effect on the ground motion field of foundation truncated boundary is deeply analyzed The results show that the magnifying effect and non-uniform effect of the peak displacement on the valley surface are significantly enhanced by oblique incidence, and the maximum peak displacement is more than 5 times that of the incident ground motion; When the bottom width of the valley is large, the edge effect of the sedimentary valley is obvious; when the bottom width is small, the focusing effect of the sedimentary valley is obvious, and the surface maximum appears in the center of the valley;The slope of the slope has a strong influence on the seismic response at the surface near the inner and outer surface of the wedge,which can be explained by the functional relationship between the interference region of the surface refraction wave and the slope、incident angle and wave velocity；With the increase of impedance ratio, the amplitude of displacement is magnified more significantly, and when oblique incidence, the weak sedimentary layer with smaller stiffness acts as a barrier to seismic wave propagation；Whether it is a hollow valley or a sedimentary valley, the scattering effect has an obvious influence on the ground motion field at the boundary.Compared with the flat bedrock free field, the maximum error of the bottom boundary and right boundary can be up to 30.8% and 54.8%.The total field considering scattering effect should be taken as input.
宋志强1，赵磊超1，王飞1，只炳成2，刘云贺1. 基于IBIEM的SH波斜入射沉积河谷场地地震动特性分析[J]. 振动与冲击, 2023, 42(9): 1-10.
SONG Zhiqiang1, ZHAO Leichao1, WANG Fei1, ZHI Bingcheng2, LIU Yunhe1. Ground motion characteristics analysis of sedimentary valley site with SH wave oblique incidence based on IBIEM. JOURNAL OF VIBRATION AND SHOCK, 2023, 42(9): 1-10.
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