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-  2015 

标贯击数液化判别方法的比较
Comparison of Standard Penetration Test (SPT) Methods for Evaluating Seismic Liquefaction Potential

DOI: 10.3969/j.issn.1000-0844.2015.03.0794

Keywords: 砂土液化,判别方法,临界标贯击数
sand liquefaction
,evaluation method,critical SPT blow counts

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Abstract:

依据标贯击数进行液化判别的方法,国外以NCEER推荐方法(改进Seed法)为代表,国内以《水利水电工程地质勘察规范》(GB50487-2008)和《建筑抗震设计规范》(GB50011-2010)为代表。NCEER方法与国内规范方法所依据的地震液化现场调查资料不同,采用的液化判据、反映震级影响的方法和考虑黏粒含量影响的方法也不同。将NCEER方法以液化临界标贯击数与深度的变化曲线表示,并将其与国内规范方法确定的液化临界标贯击数随深度的变化曲线进行比较。结果表明,在相同烈度下:近震时,国内规范方法偏于安全;远震时,对于7.5级以下地震,国内规范方法偏于安全;对于7.5~8.5级地震,在一定加速度(烈度)下,NCEER方法与国内规范方法计算液化临界标贯击数接近,某些加速度(烈度)下NCEER方法偏于安全,某些加速度(烈度)下国内规范方法偏于安全。研究成果可为《水工建筑物抗震设计规范》的修订提供参考。
For the standard penetration test (SPT) method for evaluating seismic liquefaction potential,the liquefaction potential evaluation method recommended by the National Center for Earthquake Engineering Research (NCEER) is typically applied abroad;however,methods recommended by the code for geological investigation of water resources and hydropower engineering (GB50487-2008) and that for seismic design of buildings (GB50011-2010) are used domestically.These methods different in the following aspects:(1) earthquake liquefaction field investigation data;(2) liquefaction criterion;(3) method for reflecting the influence of earthquake magnitude;and (4) method for considering the influence of fines content.In this paper,the method recommended by NCEER is expressed by the curve of critical liquefaction blow count versus depth;a comparison is made between this curve and that determined by domestic methods.Under the same intensity,domestic methods tend to be safe for near earthquakes and distant earthquake with magnitude less than 7.5.For earthquakes with magnitudes of 7.5~8.5,critical liquefaction blow counts calculated by using the NCEER method are close to that calculated by domestic methods under specific acceleration,which tends to be safe depending on the specific acceleration.For distant earthquakes (design earthquake group 2),under the magnitude of M=8.0 and seismic intensity of Ⅶ and Ⅸ,the critical liquefaction blow counts calculated by the different methods are very close;under the intensity of Ⅷ,the NCEER method tends to be safe.For distant earthquakes (design earthquake group 3),the domestic methods tend to be safe with magnitude not more than 8.0.With the magnitude of M=8.5 and acceleration amax=0.3g,the critical liquefaction blow counts calculated by the different methods are close.The NCEER method tends to be safe with acceleration less than 0.3g,whereas the domestic methods tend to be safe with that more than 0.3g.For domestic methods,under distant earthquakes (design earthquake group 2),the critical liquefaction blow counts calculated by the different methods are close with a difference of less than 2.5 blow counts.The method used in the code

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