国内外静力触探液化判别方法对比检验

Comparison and validation of cone penetration test-based liquefaction evaluation methods

静力触探试验(cone penetration test,简称CPT)具有独特优势,使其成为了海上风电工程的主要勘察方法。海上风电工程位于液化易发区,因此研究基于CPT液化判别方法的适用性和可靠性就成为亟待解决的突出问题。详细介绍了4种国内外具有代表性的CPT液化判别方法,并采用理论分析及大量CPT液化实测数据检验,对现行的美国国家地震工程研究中心(National Center for Earthquake Engineering Research,简称NCEER)方法、《岩土工程勘察规范》(GB50021-2001)方法(岩规法)、《软土地区岩土工程勘察规程》(JGJ 83-2011)方法(软土规程法)和《建筑工程抗震性态设计通则》(CES 160:2004)方法(通则法)等4种方法进行对比检验,提出了4种主要方法的评价结果。结果表明:NCEER法液化判别临界线在低烈度区存在不合理的回弯现象,在高烈度区存在临界值增大过快的问题,在Ⅶ度区深层偏于危险,在Ⅸ度区深层明显偏于保守,在Ⅶ、Ⅸ度区浅层和Ⅷ度区判别结果较好;岩规法液化判别临界线存在很大的问题,液化判别临界线随深度递减,液化判别时在Ⅶ度区浅层偏于危险,在深层明显偏于危险,在Ⅷ、Ⅸ度区浅层偏于保守,在深层偏于危险;软土规程法液化判别临界线在土层深度约6 m处存在不合理的回弯现象,在Ⅶ度区浅层判别较好,在Ⅸ度区浅层偏于保守,在不同烈度区深层均偏于危险;通则法液化判别临界线是符合目前认知的,在不同烈度区和深度下的判别效果是最好的。研究成果可为相关规范修订和工程应用提供参考与支持。

Cone penetration test(CPT)has been widely used in offshore wind power projects due to its characteristics.Offshore wind power projects are located in areas prone to liquefaction.It is particularly important to study the applicability of CPT-based liquefaction evaluation methods.In this paper,four representative CPT liquefaction evaluation methods are introduced in detail.These include the method from the National Center for Earthquake Engineering Research(NCEER),the method from the Code for investigation of geotechnical engineering(GB 50021-2001),the method from the Specification for geotechnical investigation in soft clay area(JGJ 83-2011)and the method from the General rule for performance-based seismic design of buildings(CES 160:2004).Through the analysis of the critical liquefaction lines of four methods and the test using the CPT liquefaction database,the applicability of the four methods was analyzed.The results indicate that the critical liquefaction line of National Center for Earthquake Engineering Research(NCEER)method turns back in the intensity site,the critical value increases too fast in the intensity site,and theⅦⅨevaluation is dangerous in the deep layers in the intensity site and obviously conservative in the deep layers in the intⅦⅨensity site.The NCEER method shows better evaluation results in the shallow layers ofⅦandⅨintensity sites and in theⅧintensity site.There is a problem in the critical liquefaction line of the Chinese investigation of geotechnical engineering code method.The critical value decreases with depth.The evaluation is dangerous in the shallow layers of theⅦintensity site and more dangerous in the deeper layers,while in theⅧandⅨintensity sites,it tends to be conservative in the shallow layers and dangerous in the deeper layers.The critical liquefaction line of Chinese specification for geotechnical investigation in soft clay area method turns back at a buried depth of about 6 m,and the evaluation is dangerous in the deep layers.This method shows better evaluation results in the shallow layers ofⅦintensity site,while in theⅨintensity site,it tends to be more conservative in the shallow layers.However,in various intensity sites,it consistently leans towards danger in the deeper layers.The Chinese general rule for performance-based seismic design of buildings method has a high and balanced discriminant success rate for different seismic intensities and buried depth of sand.The analytical results provide theoretical basis and support for the revision of relevant specification and engineering applications in China in the future.