抄録
The present paper is concerned with the transient states of stresses and deformations around the lined and unlined tunnels during the passage of traveling waves. In the analysis, the tensor code and the finite element method are used and three types of surrounding media are assumed, such as the linear elastic medium, and the elasto-plastic media with yield criteria of von Mises as well as of Drucker. The lining material is assumed linear elastic. The traveling waves discussed are the step-shaped and the bell-shaped.
The following results were obtained;
(1) The results obtained by the finite element method well coincide with those obtained by the tensor code analysis as well as those by the analytical procedure.
(2) The transient maximum stress concentrations are generally lower those under the static loading of the same intensity as the traveling waves.
(3) The transient stress concentration due the single half-sinusoidal wave is almost equal to the stress concentration of the steady-state due to the sinusoidal harmonic wave train, so long as the wave length is larger than approximately three times of the radius of circular tunnel. As the wave length decreases, the maximum stress concentration decreases.
(4) For the lined tunnel, as the lining becomes stiffer, stresses become higher in the lining whereas lower in the surrounding medium. The rate of increase of the stress concentration factor is slightly less than the ratio of the Young's modulus of the lining to that of the medium.
(5) The stiffer the lining is, the smaller the yielded zone becomes. However, the properties of the surrounding media have little effect on the stresses in the lining.
(6) A wide yielded zone may be formed in the surrounding medium in the source side of the traveling wave due to the reflected tensile wave from the tunnel.
