土层结构对油气管线工程地震动峰值加速度区划图的影响研究

油气管线工程是生命线工程的重要组成部分,工程跨度通常超越几十甚至几千公里,从而导致横穿地区覆盖层中土层结构存在明显差异,对地震动峰值加速度(PGA)产生较大影响,进而影响区划结果。本文采用分区拟合放大系数的方法,对华北平原地区某大型管线进行研究,给出研究区不同土层结构条件下场地放大系数KS-基岩PGA拟合函数结果,得到沿线附近10km范围内的PGA区划图结果,并与第四代和第五代中国地震动参数区划图提出的场地系数公式的计算结果进行比较。三种计算方法的结果表明,研究区内50年超越概率10%条件下实际场地放大系数为1.30~1.45,50年超越概率5%条件下实际场地放大系数为1.15~1.30,均高于我国第四代和第五代区划图对场地系数的建议值。50年超越概率10%下的PGA区划图结果显示,局部区域在第四代和第五代地震动参数区划图场地系数的结果中位于0.15g或0.20g区,由于KS的提高,其实际计算结果会提升为0.20g或0.25g分区,这说明场地系数对峰值加速度区划图结果具有较大影响。

Influence of Soil Layer Structure on Seismic Peak Ground Acceleration Zonation Maps of Oil and Gas Pipeline Project

Oil and gas pipelines are vital aspects of infrastructure projects and may span tens or even thousands of kilometers.These spans may involve different soil structures that may become overburdened and thus considerably affect the seismic peak ground acceleration (PGA) and PGA zonation map. In this study,based on the site amplification coefficient,we examine a gas pipeline project in the North China plain. We estimate the fitting functions of the site amplification coefficient (K_S) and PGA of rocks in different soil layer constructions and obtain a PGA zonation map for the adjacent 10 km area.We then compare our results with those given by the 4^th and 5^th seismic ground motion parameter zonation maps of China.The results show that the practical amplification coefficient K_S lies between 1.30 and 1.45 for 10% probability of exceedance in 50 years,and the amplification coefficient K_S lies between 1.15 and 1.30 for 5% probability of exceedance in 50 years.They are both relatively larger than the values suggested by the 4^th and 5^th zonation maps.The PGA zonation map with 10% probability of exceedance in 50 years shows that local regions belonging to 0.15g or 0.20g zones in the 4^th and 5^th zonation maps of China become 0.20g or 0.25g zones,which demonstrates that the amplification coefficient K_S may significantly influence PGA zonation map classifications.