Consideration of Earthquake Damages for the Dangerous Tanks to the 1995 Hyogo-ken Nanbu Earthquake : Warning to the Existing Facilities in the Metropolitan Area

1995年1月の兵庫県南部地震において甚大な被害を受けた神戸港湾地域は日本有数の工業地帯であり、石油コンビナート等特別防災区域の指定地区も含まれていた。幸いにして危険物施設に関しては、新潟地震時のように大規模な火災こそ発生しなかったが、2,000klの高圧ガス施設からのLPガスの漏洩事故も生じ、屋外タンク貯蔵所の被害状況は決して楽観できるものではなかった。あと数秒間地震動が続いていたら、貯槽や配管の変形、破損により多くの屋外タンク貯蔵所から内容物の漏洩が始まり、新潟地震を大きく超える大火災が生じる危険性も大いに考えられる状況であった。一方、首都圏は人口の密集度、危険物・高圧ガスの集積度において、兵庫県南部地震の被災地をはるかにしのぐ状態となっている。本稿では新潟地震及び兵庫県南部地震の危険物施設などの被害状況とその経験をとおして、首都圏の危険物・高圧ガス施設の地震対策の問題を考察している。This report deals with the earthquake damages to the industrial facilities and the associated counterplanning，in particular，those located in the metropolitan area. At the Hyogo-ken Nanbu Earthquake on January 17th，1995，enormous structures in the industrial facilities were damaged by excessive seismic force and liquefaction caused in the coast side area. From one of the huge pressurized gas storage tanks，leakage of LP-gas occurred due to excessive pipe deformation by lateral flow of the soil foundation. Through the investigations of the typical damage to the facilities having dangerous object auch as oil storage tanks，high pressure gas tanks and pipings by the Hyogo-ken Nanbu Earthquake and the Niigata Earthquake on June，1964，comparative examination on the industrial structure damages was carried out. Several major damage modes to the storage tanks was selected such as the roof damage，the damage on the connecting parts between the roof and wall，the liquefaction induced damage，the pull-out of the anchor bolts and so on. Finally，the author gave suggestions for the anti-earthquake counter planning to the industrial facilities located in Tokyo metropolitan area. Totally 6,350 tank facilities are now to being setting up along the Tokyo Bay area which is approximately double of those in the Hanshin area. The importance of the urgent countermeasure was pointed out to the lateral flow due to the soil liquefaction and the available techniques for reducing the relative motions generated among structures，equipments and pipings