基于子结构法的成层场地中沉积河谷的散射分析

土层场地对地震动的影响明显，研究成层场地局部复杂地形的波动场特性，对于抗震设防具有重要意义。基于土-结构相互作用理论，含有局部复杂地形的成层场地，可分解成广义结构（即近场复杂地形及其周围土体）和具有规则开挖边界的成层无限地基（即远场）。远场的格林函数可通过精细积分求解频域-波数域内的对偶波动方程获得，利用傅里叶逆变换得到频域-空间域内的柔度矩阵。近场可采用比例边界有限元进行模拟，通过高性能连分式的传递边界求解动刚度。自由场波动可通过传递矩阵法求得，将动刚度和自由场波动位移代入控制方程即可得到散射场的动力响应。数值算例验证了方法的准确性，并利用提出的方法讨论含有软夹层场地局部复杂场地的波动场特性。

Analysis of scattered field characteristics of valley embedded in layered soil

Site effects can generate large ground motion amplification during earthquakes, and it is important to study the wave field characteristics of layered soil. A new model was presented to compute the diffraction of P and SV waves by a valley embedded in multi-layered half-space. Based on the theory of soil-structure-interaction, the response of scattered wave field could be achieved by the response of free wave field. The layered half-space could be decomposed into near field (the generalized structure, composed of the structure itself and its surrounding soil) and far field (the infinite layered half-space with regular boundaries). The near and far fields of multi-layered half-space were modeled by scaled boundary finite element method (SBFEM) and high-accuracy precise integration method (HPIM), respectively. The dynamic flexibility coefficients of the far field were solved in the frequency-wave number domain by using the precise integration method and then the results were transformed by the inverse fast Fourier transform within the frequency-space domain. The dynamic stiffness of near field was solved by a continued-fraction-based high-order transmitting boundary of SBFEM. Numerical examples were provided to validate the accuracy and efficiency of the proposed approach. In order to give perspective on the range of effects caused by the trapezoid valley embedded in the soft interlayer site, some examples were presented as well.