场地动力特性对衬砌隧道地震反应的影响

采用间接边界元法(IBEM),研究了平面SV波入射下场地动力特性对衬砌隧道地震反应的影响问题。充分利用半空间格林函数和全空间格林函数在分别构造含孔半无限空间域和闭合域内散射波场方面的优势,将含有衬砌隧道的层状半空间分解为含孔层状半无限空间域和一个环形衬砌闭合域。在半无限空间域孔洞边界和闭合域边界各单元上分别施加虚拟均布荷载,进而求得半空间和全空间域内的位移、应力格林函数,然后根据边界条件确定虚拟均布荷载密度,最后求得衬砌内表面动应力集中系数。验证了方法的正确性,并以基岩上单一土层和基岩上三层土为例,计算分析了层状弹性半空间中隧道衬砌内表面动应力集中系数。结果表明,随着基岩土层刚度比的增大,动应力集中系数峰值减小;随着土层厚度增大,动应力集中系数峰值总体上呈减小趋势;对于不同土层层序,动应力集中系数峰值明显不同。

Effects of Site Resonant Characteristics on the Seismic Response of Lined Tunnel

The effects of site resonant characteristics on the seismic response of lined tunnel under plane SV-waves are studied by adopting indirect boundary element method (IBEM). Exploring the advantages of both the half-space Green''s functions for the excavated half-space domain and full-space Green''s functions for the enclosed domain, the model of lined tunnel buried in layered elastic half-space is decomposed into a closed circle region and a excavated layered elastic half-space region. The fictitious distributed loads are applied both on elements of the tunnel surface in layered half-space domain and of the enclosed boundary to calculate Green''s functions for the displacements and stresses, and then the amplitudes of the fictitious distributed loads are determined from the boundary conditions to obtain the coefficient of dynamic stress concentration on lining inner surface. The method is verified and the coefficient of dynamic stress concentration around a lined tunnel in layered elastic half-space is investigated with the model of single and three soil layers over bedrock. Result shows that the coefficient amplitudes increase with the increasing of bedrock-to-soil layer stiffness ratio, while decrease with the thickening of layer on the whole, and they have very different amplitude for different layer sequences.