Effect of Dynamic Stiffness of Foundation on Seismic Response of Underground Pipeline to Random Ground Motion

The response of underground pipeline is affected directly by the variation of dynamic stiffness of founda-tion with frequency.Based on Mindlin solution and dynamic basic solution of elastic half-space,static stiffness and dynamic stiffness of foundation were obtained respectively,then seismic responses of underground pipeline in both longitudinal and lateral directions in uniform medium were calculated respectively by pseudo-excitation method in random vibration theory.The results show that with the increase of buried depth,dynamic stiffness is more and more sensitive to the change of frequency,and is obviously different from the static one;and essentially due to the low-frequency characteristic of auto-power spectral density(PSD) function of ground displacement,namely,regarded as seismic input,auto-PSD function of ground displacement is effective in the low-frequency range,and almost zero in the high-frequency range,dynamic stiffness could be replaced approximately by the static one.