This paper deals with a series of experimental studies on the dynamic behavior of pipe with a ball type flexible joint that was buried in the liquefied ground. Two different sizes of shaking table test are used to investigate the behavior of pipe, one to house an actual size pipe and the other to contain a miniature size pipe. In larger size shaking table test, a large size diameter pipes with a length of 8.1 m were subjected to seismic loading in longitudinal direction. In smaller size shaking table test, the shaking of ground was applied to a small size pipe by varying the direction of shaking from the longitudinal direction to the direction normal to the pipe. In both series of tests, the dynamic behaviors of pipes were measured together with the monitoring of ground movements and stress changes. All of the tests have indicated that large movement of pipe started when the ground liquefaction began, and the dynamic behavior of flexible pipe in liquefied ground was successfully measured.
During the 1995 Kobe Earthquake, there were extensive damages on the lifeline facilities, such as buried pipe-lines of water and gas. The cause of damages are partly due to the very strong ground vibration during the earthquake, but also the liquefaction of ground is thought to have played a significant role in causing damages especially on those facilities located along the coast line of the Osaka Bay. It is know from the post earthquake reconnaissance of damaged pipe lines that the buried pipes had suffered damages in the form of extrusions at the pipe joint and shear failures at the pipe section, (Hamada et al. (1996)). It is also known that the amount of deformations was very large especially in reclaimed lands where the liquefaction had inevitably occurred.
