基于原位试验的砂土地震液化判别方法对比分析

Comparative analysis of discrimination methods for seismic liquefaction of sand based on in-situ tests

目前国外判别地震液化公式主要是基于Seed和Idriss提出的简化方法,比较循环应力比(CSR)与循环抗力比(CRR)之间的关系来判断是否液化。CRR的计算多是利用历史上基于原位试验地震液化数据进行拟合,因此不同学者的拟合公式有较大区别。针对上述区别,选取国外某港口项目的原位试验数据,采用美国地震工程研究中心(NCEER)推荐的液化判别方法与Boulanger和Idriss判别法进行对比分析。得出以下结论:1)基于SPT试验,上述两种方法安全系数差别不大;基于CPT试验,Boulanger和Idriss方法较为保守。2)NCEER方法对预测地震液化可靠性较高,而Boulanger和Idriss方法对工程适应性较强。3)在进行国外相关工程设计时,宜采用两种以上方法进行计算并相互验证。

At present,the formula for discriminating seismic liquefaction in foreign countries is mainly based on the simplified method proposed by Seed and Idriss,which compares the relationship between cyclic stress ratio(CSR)and cyclic resistance ratio(CRR)to determine whether liquefaction is possible.Historical seismic liquefaction data of in-situ tests are mostly utilized for fitting in the calculation of CRR,which makes the fitting formula of different scholars quite different.In view of the above differences,the in-situ test data of a foreign port project are selected in this paper,and a comparative analysis is conducted between the liquefaction discrimination method recommended by the US National Center for Earthquake Engineering Research(NCEER)and the discrimination method of Boulanger and Idriss.The following conclusions are drawn:1)The standard penetration test(SPT)reveals that the two methods have little difference in safety factors.The results of the cone penetration test(CPT)indicate that the method of Boulanger and Idriss is conservative.2)The NCEER method has high reliability for predicting seismic liquefaction,while the method of Boulanger and Idriss has strong engineering adaptability.3)In the design of relevant foreign projects,two or more methods should be used for calculation and mutual verification.