顺层岩体隧道地震行波效应的不对称性

Asymmetry of Traveling Wave Effect of Seismic on Tunnel in Bedding Rock Mass

因地震波斜入射而产生的行波效应会显著增加隧道结构的内力和位移响应,从而对隧道抗震产生不利影响。为研究顺层岩体隧道地震行波效应的特征,对qP波斜入射方向与隧道纵断面相平行的工况,考虑顺层岩体的横观各向同性本构关系,应用波动分析方法并采用ANSYS进行地震响应数值分析。以某顺层岩体中高铁深埋隧道为工程背景,研究岩层倾角和岩层各向异性对隧道洞身段地震响应行波效应的影响。结果表明:当岩层水平或竖直时(即岩层倾角为0°或90°),隧道横断面左右对称位置上位移分量中隧道轴线方向的相对位移分量相同,这意味着顺层岩体隧道的地震行波效应左右严格对称,即横断面仍为平面;而岩层倾斜时(即岩层倾角不为0°或90°),隧道横断面左右对称位置上位移分量中隧道轴线方向的相对位移分量却不等,这意味着隧道横断面扭成不规则且不对称的曲面;随着岩层倾角的增大,曲面不对称性先增强后减弱(约倾角为45°时最强),呈非线性关系。此外,又进一步研究了岩层各向异性强度对行波效应的影响,结果发现:当岩层倾斜时,行波效应的不对称性随顺层岩体各向异性的增强而线性增强,这意味着顺层岩体各向异性越强,隧道横断面在地震波作用下所形成不规则曲面的不对称幅度也越大。

The traveling wave effect caused by oblique incidence of seismic wave will significantly increase the internal force and displacement response of tunnel structure, which will adversely affect the anti-seismic performance of tunnel. In order to study the characteristics of the seismic traveling wave effect of tunnel in bedding rock mass, in view of the seismic qP wave oblique incident in parallel with the longitudinal section of the tunnel, considering the transversely isotropic constitutive relation of bedding rock mass, the wave numerical analysis on the seismic response is carried out by using ANSYS software and wave analysis method. On the background of a high-speed railway deep buried tunnel in a bedding rock mass, the influence of bedding rock dip angle and anisotropy on the seismic traveling wave effect of the tunnel is studied. The result shows that(1) when the rock layer is horizontal or vertical(the rock dip is equal to 0° or 90°), in the symmetrical positions of the tunnel cross section, the relative displacement components of the tunnel axis are same, showing the strictly symmetric traveling wave effect of tunnel in bedding rock mass(the cross section is still plane);(2)while the rock layer is inclined(the rock dip is not equal to 0° or 90°), in the symmetrical positions of the tunnel cross section, the relative displacement components of the tunnel axis are not same, which shows that the tunnel cross section is twisted into an irregular and asymmetric curved surface;(3) as the dip angle of rock layer increases, the asymmetry of the curved surface increases first and then decreases(the asymmetry is the strongest when the dip angle is about 45°). In addition, the influence of rock anisotropy strength on traveling wave effect is further studied. The result shows that when the rock layer is inclined, the asymmetry of seismic traveling wave effect increases linearly with the enhancement of rock anisotropy. This means that the stronger the bedding rock anisotropy is, the greater the asymmetry of the irregular curved surface formed by cross-section of tunnel under the action of wave will be.