New evaluation formula for sand liquefaction based on survey of Bachu Earthquake in Xinjiang
-
摘要: 以新疆巴楚—伽师 Ms6.8 级地震液化现场勘察和测试为基础，获取了 47 个场地的标准贯入试验资料，分析了现有基于标准贯入的砂土液化判别方法的适用性，提出了新的砂土液化判别公式。分析表明国内外现有基于标准贯入击数的砂土液化判别公式不适用于新疆地区，中国现有规范对此次巴楚地震非液化点判别成功率 88% ，但对液化场地判别成功率仅为 38% ，会给出明显偏于危险的结果。以新调查数据建立的砂土液化判别模型由地震烈度、实测标准贯入击数、标准贯入击数基准值、地下水位、砂土埋深等 5 个参数构成，其中标准贯入击数基准值以及地下水位和砂土埋深的影响系数分别采用归一化方法和本文提出的优化方法给出。与中国现有规范相比，新疆巴楚液化土层有所增加，推导出的标准贯入击数基准值远小于现有规范，表明巴楚地区抗液化能力显著低于以往形成我国规范时调查的可液化场地，深层土和低水位砂层液化可能性更大。所建立的砂土液化判别新公式，液化回判成功率为 91% ，非液化回判成功率为 85% ，表明构建的模型合理，计算公式可靠，同时新公式延续了中国现有规范的基本形式，工程使用方便，可为新疆地区区域性规范制订提供参考。Abstract: The in-situ SPT data at 47 sites have been collected in the liquefaction survey of Bachu Ms 6.8 Earthquake, Xinjiang, China. The feasibility of the existing sand liquefaction evaluation methods is analyzed, and a new evaluation formula is proposed. The analysis shows that the current assessment formulae using SPT for sand liquefaction are not applicable in Xinjiang area, which will present obvious risky results. Based on new investigation data, five parameters including seismic intensity, measured SPT values, datum SPT values, water tables and depths of sandy soils are included in the new liquefaction evaluation model. The datum SPT values, the influencing coefficients of water tables and sand depths are gained by a normalized method and by an optimizing method, separately. The characteristic depths of sand are larger than those in the existing Chinese seismic design codes, and the datum SPT values are far larger than those in the code, indicating that the possibility of deep sand liquefaction under low water tables is high in Bachu Earthquake. The successful judging rates by the new formula are 86% and 88% for liquefied sites and for non-liquefied sites, respectively. The proposed new formula can be employed for site liquefaction evaluation and regional code formulation in Xinjiang area.
-
Keywords:
- sand liquefaction /
- SPT /
- evaluation formula /
- Bachu Earthquake of Xinjiang
-
[1] YOUD T L, IDRISS I M. Proceedings of the NCEER workshop on evaluation of liquefaction resistance of soils[R]. NY: NCEER-97-0022, Buffalo, 1997. [2] SEED R B, CETIN K O. Recent advances in soil liquefaction engineering, a unified and consistent framework[R]. USA: Earthquake Engineering Research Center, 2003. [3] 汪闻韶 . 土体液化与极限平衡和破坏的区别和关系 [J]. 岩土工程学报 , 2005, 27 (1): 1 – 10. (WANG Wen-shao. Distinction and interrelation between liquefaction state of limit equilibrium and failure of soil mass[J]. Chinese Journal of Geotechnical Engineering, 2005, 27 (1): 1 – 10. (in Chinese)) [4] 刘恢先 . 唐山大地震震害 [M]. 北京 : 地震出版社 , 1989. (LIU Hui-xian. Tangshan Earthquake damage [M]. Beijing: Seismic Press, 1989. (in Chinese )) [5] BRADY RAY COX. Development of a direct test method for dynamically assessing the liquefaction resistance of soils in situ[D]. Austin: The University of Texas at Austin, 2006. [6] 胡聿贤 . 地震工程学 [M]. 北京 : 地震出版社 , 1988. (HU Yu-xian. Earthquake engineering[M]. Beijing: Seismic Press, 1988. (in Chinese)) [7] 李兆焱 , 袁晓铭 , 曹振中 , 等 . 标准贯入法对巴楚地震液化场地适用性及误判原因分析 [J]. 世界地震工程 , 2010, 26 ( 增刊 1): 282 – 286. (LI Zhao-yan, YUAN Xiao-ming, CAO Zhen-zhong, et al. SPT method’s feasibility for Bachu earthquake liquefied and analysis of its miscarriage[J]. World Earthquake Engineering, 2010, 26 (S1): 282 – 286. (in Chinese)) [8] 中华人民共和国国家标准编写组 . GB50011 — 2001 建筑抗震设计规范 [S]. 北京 : 中国建筑工业出版社 , 2001. (The National Standards Compilation Group of People ¢ s Republic of China. GB0011 — 2001 Code for seismic design of buildings[S]. Beijing: China Architecture and Building Press, 2001. (in Chinese)) [9] YOUD T L, IDRISS I M. Liquefaction resistance of soils: summary report from the 1996 NCEER and 1998 NCEER/NSF workshops on evaluation of liquefaction resistance of soils[J]. Journal of Geotechnical and Geoenvironment Engineering, 2001, 127 (4): 297 – 313. [10] SEED H B, IDRISS I M. Ground motions and soil liquefaction during earthquakes[M]// Earthquake Engineering Research Institute Monograph, 1982.
计量
- 文章访问数: 1422
- HTML全文浏览量: 1
- PDF下载量: 554
下载:
