Damage to buried water supply pipelines in the chichi (Taiwan) earthquake and apreliminary evaluation of seismic resistance of pipe joints

This paper gives a brief description of the damage to the public water supply pipelines in the central Taiwan area due to the strong earthquake shock (M=7.3) on September 21, 1999. Field investigation of water supply systems near the earthquake epicenter was conducted, and results were summarized as: (1) the intensive faulting movement was irresistible to the pipeline system; (2) the pipeline damage was closely related to the induced ground shaking, whereas the damage grade mainly depended upon the size of pipeline diameter; (3) the damage was affected by the site amplification of ground shaking and liquefaction due to poor local ground condition; (4) different pipeline materials exhibited different damage types. The investigation indicates that pipe fitting connections are apt to suffer damage, and the pipe joint is the key point of earthquake resistance. Laboratory tests of pipe joints are conducted to examine the cyclic load resistance for the locally used ductile iron pipe and polyvinyl chloride pipe. Test results show that rigid joints on polyvinyl chloride pipes are vulnerable to earthquake, while flexible joints on both polyvinyl chloride and ductile iron pipes are capable of being elongated and have better earthquake resistance. This study believes that measures for improving the seismic resistance of pipe joints are valuable for future research.