关键词: 海上风电工程, 地震效应, 原位测试, 静力触探测试, 液化场地判别

Abstract: 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 Ⅶ intensity site, the critical value increases too fast in the Ⅸ intensity site, and the evaluation is dangerous in the deep layers in the Ⅶ intensity site and obviously conservative in the deep layers in the Ⅸ intensity site. The NCEER method shows better evaluation results in the shallow layers of Ⅶ and Ⅸ intensity sites and in the Ⅷ intensity 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 the Ⅶ intensity site and more dangerous in the deeper layers, while in the Ⅷ and Ⅸ intensity 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 of Ⅶ intensity site, while in the Ⅸ intensity 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.

Key words: offshore wind power project, seismic effect, in-situ test, cone penetration test, evaluation of liquefaction site