| 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,and therefore it is difficult to study the seismic response mechanisms and characteristics.So,in this dissertation,on the one hand,strain calculation formulas of transversely isotropic media under seismic wave action were put forward,and seismic wave input method as well as the corresponding formulas were established.The method was combined the FEM with time-domain wave and adopts approximate viscous-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 seismic wave in rock mass and the traveling wave effect caused by inclined seismic waves.On the other hand,the relationship between the asymmetry or non anti-symmetric of the response and the dip or the rock anisotropy were also studied by using the method,and the correlative conclusions were obtained.The main results and conclusions are as follows:1)A wave numerical method for seismic response of tunnels in bedding strata was put foward:(1)The particle motion law of transversely isotropic medium under the seismic wave action is analyzed,and then strain calculation formulas of transversely isotropic medium described by the stress time history were put forward.Also,the longitudinal components of qSV wave or shear components of qP wave that should be ignored in the wave numerical simulation were pointed out.(2)Seismic wave field of tunnel in bedding rock mass was analyzed,and the corresponding wave input method and formulas were established.The method is applicable to the cases of the oblique incidence direction of earthquake wave in parallel with the longitudinal section of the tunnel or perpendicular to the tunnel axis respectively,and the feasibility,rationality and reliability of the method were verified.(3)According to the principle that the intensity of seismic wave input at the artificial boundary is consistent with that of the original continuum,the approximate viscous-elastic boundary for transversely isotropic medium was proposed by changing the spring coefficient and damping coefficient of viscous-elastic boundary for isotropic medium.2)A simple and idealized theoretical analysis for the case of the oblique incidence of seismic wave is perpendicular to the tunnel axis was carried out,and the distribution functions of force acting on lining of circular tunnel were deduced.Then the internal forcedistribution characteristics of tunnel lining were obtained by using the functions,and the characteristics are consistent with the results of the wave simulation analysis,the findings further verify the rationality of the wave method proposed in this dissertation.3)The relation between the asymmetry(for qP wave incidence)/non anti-symmetric(for qSV wave incidence)of seismic response of tunnel in bedding rock and the dip(or the anisotropy strength of rock stratum)was discussed.The main conclusions are as follows:The asymmetry/non anti-symmetric of the seismic response of tunnel does not obey the linear relationship with the change of the dip angle.The relationship is segmented,different intervals under different working conditions,but in each interval,the asymmetry increases first and then decreases with the increase of the dip angle;The seismic response is left-right symmetrical/anti-symmetric strictly when the rock is horizontal or vertical.The asymmetry of seismic response increases gradually with the increase of rock anisotropy,and obeys the approximate linear relation.And the non anti-symmetry of seismic response is lack of uniform and clear rules,depending on the dip angle. |
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