| Summary: | 碩士 === 國立聯合大學 === 土木與防災工程學系碩士班 === 105 === In this study, the strata are extended to monoclinic damped media to reflect the phenomenon that the energy is attenuated when waves propagating in the complex anisotropic damped media.
The theme is divided into two parts. In the first part, the transient responses in the monoclinic damped media are solved by the generalized ray theory, in which the ray integrals of transient responses in the full space are derived first, then the ray integrals in parallel layered media are obtained by the ray theory, and then the inverse Laplace transform of each integral is solved by the Cagniard method to obtain the fundamental solutions of impulsive and Heaviside step source time functions. Then the displacement of the general source time functions can be obtained from the convolution of fundamental solutions with its general source time function.
In the second part, we employ the phase function and travel time of each ray integral to deduce its ray velocity and phase velocity, and then investigate the ray angle and phase angle of each ray segment and their relationships. We found that the wave front of each ray in monoclinic damped media is oblique ellipse, that is in the case of the same angle of rays, ray velocities are different in the first, third quadrants from in the second and fourth quadrants; in addition under the same phase angle, phase velocity is also divided into similar two situations. Moreover the ray angles are independent of the damping ratio but its ray velocity is increasing with the damping ratio.
The major elastic constants for SH waves in the monoclinic media are c_44, c_66 and c_46, which are complex in damped media causing the faster speed. Finally from the numerical results of the responses caused by the source time functions of the Heaviside step and the octahedral polynomial functions showed that the variations of the elastic parameters and damping ratios have a great influence on the responses.
|
|---|
