云南阳宗海电厂场地的地震地质条件评价

ON THE SEISMOGEOLOGICAL CONDITIONS FOR YANGZONGHAI THERMAL POWER PLANT, YUNNAN PROVINCE

云南阳宗海火电厂地处小江强震带内,其地震烈度原定为Ⅸ度,严重地影响了该厂改扩建工程的可行性。近几年有关单位,作了厂址的地震地质、工程地质和地震危险性分析,使该厂能以基本烈度为Ⅷ度标准设防扩建。本文简要地介绍该电厂场地的地震地质条件,旨在以此为例,表明即使在强震的高烈度地区,经过严谨的科学论证,仍可选出国家建筑抗震设计规范所允许的火电厂厂址,可供今后类似工程参考。

The Yangzonghai thermal power plant is located in Xiaojiang strong seismic zone, Yunnan province. Fundamental earthquake intensity of the area is Ⅸ degrees. This puts a great constraint on the further extension of the plant, which is necessary to make full use of the favourable power supply to Yunnan province.The Xiaojiang fault zone consists of two branches (the east and west branches) and the site of the plant is located in between both of them being strong seismic activity zone in history. An earthquake of magnitude 8 occurred in 1833 near Song-Ming county on the west branch.A geological cross-section was dug in Dongguyayin village, it is found that the recurrence for magnitude 7 is at least 300 years and magnitude 8 is at least 1000 years. So there is little possibility for an earthquake over magnitude 7 to occur in coming 100 years.Geomorphologically plant area is shown as terrace, with a low relief. The bedrock consists of dolomite. The rock formation gently dips away from the lake Yangzonghai and underlies the red clay. The underground water level is deep. All of these suggest that the foundation of the plant is steady, more beneficial for antiseismic building.As stated above, it is clear that the fundmental earthquake intensity of the Yangzonghai power plant can be lowered from Ⅸ down to Ⅷ degrees.