顺层岩体是隧道工程中常见的地质情况,震害突出,但尚无有效的地震响应分析方法,因而难以深入研究其响应机制和规律。为此,建立一种地震波动输入方法及相应公式,该方法以有限元法与时域波动分析法相结合,采用黏弹性人工边界,基于顺层岩体的横观各向同性本构关系,考虑岩体中地震波的偏振特性和相速度变化特点,适用于地震波斜入射方向与隧道纵断面平行的情况。同时,为验证所提出方法的实用性和可行性,应用其分析某顺层岩体中高速铁路隧道结构的地震响应规律。结果显示:当岩层水平或竖直时,则qP波引起的衬砌内力包络图对称;当岩层倾斜时,则qP波引起的衬砌内力包络图不对称,不对称性的幅度与岩层倾角相关;岩层倾角不同,则弯矩值相差较大;弯矩包络图无论对称与否,环向弯矩极值均位于拱脚处,而纵向弯矩极值却位于拱顶和仰拱处。此外,作为对比分析,又将岩层简化为各向同性介质,采用该方法进行计算,结果发现:P波引起的衬砌内力包络图对称,且内力包络图与将岩层简化为横观各向同性介质时相接近。这进一步验证了提出方法的合理性和可靠性。
The bedding rock mass is a common geological configuration in tunnel engineering. The seismic damage occurs frequently in the bedding strata,but there is no effective method of seismic response analysis. In this paper,a method of seismic wave input and a corresponding formula were established. The method combines the FEM with the analysis of the time-domain wave and adopts the visco-elastic artificial boundary. The transverse isotropic constitutive law of bedding rock mass is used with the consideration of the characteristics of polarization and phase velocity change of the seismic wave in rock mass. The method is applicable to the case of the oblique incidence direction of earthquake wave in parallel with the longitudinal section of the tunnel. In order to verify the feasibility of the method,the seismic response of a high-speed railway tunnel in a bedding rock mass was studied. The results show that,when the rock layer is horizontal or vertical,the qP wave causes the symmetric internal force envelope of lining. When the rock layer is inclined,the qP wave causes the asymmetric internal force envelope,and the amplitude of the asymmetry correlates to the dip angle of the rock layer. When the dip angles of rock layers are different,the difference of bending moments is larger. The maximum of hoop bending moment is located at the arch foot,while the maximum longitudinal bending moment is located at the vault and invert no matter the moment envelope is symmetrical or not. When the rock layer is simplified as the isotropic medium,the P wave causes the symmetric internal force envelope,which is close to the results when the rock layer is simplified as the transversely isotropic medium. The findings further verify the rationality and reliability of the method.