| 最近20年地震中场地液化现象的回顾与土体液化可能性的评价准则 |
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| 引用本文： | 陈国兴,金丹丹,常向东,李小军,周国良.最近20年地震中场地液化现象的回顾与土体液化可能性的评价准则[J].岩土力学,2013,34(10):2737-2755. |
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| 作者姓名： | 陈国兴 金丹丹 常向东 李小军 周国良 |
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| 作者单位： | 1.南京工业大学 岩土工程研究所，南京 210009；2.江苏省土木工程防震技术研究中心，南京 210009； 3.环境保护部核与辐射安全中心，北京 100082；4.中国地震局地球物理研究所，北京 100081 |
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| 基金项目： | 国家科技重大专项(No.2011ZX06002-010-15)；国家自然基金项目(No.41172258)；教育部高等学校博士学科点专项科研基金项目(No.20113221110009)。 |
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| 摘 要： | 回顾了1994年美国Northridge地震、1995年日本阪神地震、1999年土耳其Kocaeli地震、1999年台湾集集地震、2008年中国汶川地震、2010年智利Maule地震、2010~2011新西兰Darfield地震及余震、2011年东日本地震中大量的、不同类型的液化实例调查与研究,发现这些地震的液化具有以下特点:(1)罕见的特大地震(Mw9.0)使远离震中300~400 km的新近人工填土发生严重的大规模液化;(2)特大地震(Ms8.0、Mw8.8)使远离震中的低烈度Ⅴ~Ⅵ度地区发生严重液化;(3)海岸、河岸附近地区的新近沉积冲积、湖积土,填筑时间不到50年的含细粒、砂砾人工填土,容易发生严重液化;(4)天然的砂砾土层液化发生严重液化;(5)发生了深达20 m的土层液化现象;(6)松散土层液化后可以恢复到震前状态并再次发生液化;(7)高细粒(粒径≤75 m)含量≥50%或高黏粒(粒径≤5 m)含量≥25%的低-中塑性土严重液化,对介于类砂土与类黏土之间的过渡性态土,有时地表未见液化现象;(8)液化土层的深度较深或厚度较小时,容易出现地面裂缝而无喷砂现象;有较厚的上覆非液化土层时,场地液化不一定伴随地表破坏。液化实例证明,第四系晚更新世Q3地层可以发生严重液化;黏粒含量不是评价细粒土液化可能性的一个可靠指标;低液限、高含水率的细粒土易发生液化,采用塑性指数PI、含水率wc与液限LL之比作为细粒土液化可能性评价的指标是适宜的。综合Boulanger和Idriss、Bray和Sincio、Seed和Cetin等的液化实例调查与室内试验研究成果,建议细粒土液化可能性的评价准则如下:PI12且wc/LL0.85的土为易液化土,12PI≤20和/wc/LL≥0.80的土为可液化土;PI20或wc/LL0.80的土为不液化土。
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| 关 键 词： | 地震 土体液化 细粒土 塑性指数 液化可能性 准则 |
| 收稿时间： | 2013-03-30 |
Review of soil liquefaction characteristics during major earthquakes in recent twenty years and liquefaction susceptibility criteria for soils |
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| CHEN Guo-xing
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JIN Dan-dan
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CHANG Xiang-dong
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LI Xiao-jun
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ZHOU Guo-liang.Review of soil liquefaction characteristics during major earthquakes in recent twenty years and liquefaction susceptibility criteria for soils[J].Rock and Soil Mechanics,2013,34(10):2737-2755. |
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| Authors: | CHEN Guo-xing JIN Dan-dan CHANG Xiang-dong LI Xiao-jun ZHOU Guo-liang |
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| Institution: | 1.Institute of Geotechnical Engineering, Nanjing University of Technology, Nanjing 210009, China; 2. Civil Engineering & Earthquake Disaster Prevention Center of Jiangsu Province, Nanjing 210009, China; 3. Nuclear and Radiation Safety Center, the Ministry of Environmental Protection of P. R. China, Beijing 100082, China; 4. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China |
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| Abstract: | This paper reviews the characteristics of soil liquefaction-induced damage observed from the Northridge, USA earthquake, 1994, the Hanshin, Japan earthquake, 1995, the Kocaeli, Turkey earthquake, 1999, the Chi-Chi, Taiwan earthquake, 1999, in China, the Wenchuan, China earthquake, 2008, the Maule, Chile Earthquake, 2010, the Darfield and Christchurch, New Zealand earthquake, 2010 to 2011, and the great East Japan earthquake, 2011. There are several characteristics in the occurrence of liquefaction and consequence damage which are different from a number of cases experienced in these earthquakes. These are summed up as follows: (1) The unprecedented long duration of the shaking and extensive makes the occurrence of liquefaction in the newly reclaimed land, fill area is 300~400 km distant from the epicentral area attributed to the rarely encountered huge moment magnitude Mw9.0 earthquake. (2) A number of site liquefactions and lateral spreadings are observed in seismic intensity scales of Ⅴ and Ⅵ, an area of low intensity is attributed to the encountered magnitude scale Ms8.0 and Mw8.8 earthquakes. (3) Severe liquefactions in sites are observed having young alluvial, lacustrine deposits along rivers and sea bay areas, and in reclaimed land, fill area contains fine-grained soils, gravel sands in less than fifty years. (4) Severe liquefaction in natural gravel sand deposits occurs. (5) Soil liquefies in depth of 20 m. (6) Liquefaction and re-liquefaction of the sites over a large region do not result in densification of the loose deposit, future earthquakes of sufficient magnitude can again induce liquefaction. (7) Severe liquefaction occurs in low to moderate plasticity soils containing more than 50% fines content (grain size is, smaller than 0.075 mm) or more than 25% of clay content (grain size is, smaller than 0.005mm), however, field evidence of liquefaction may not be observed in transition behavior fine-grained soils between sand-like and clay-like behaviors. (8) Ground cracking without venting of sand boils is more likely as the depth and thickness of the liquefied layer increases and decreases, respectively; vented material, provided field evidence of liquefaction, may be absent due to the large depth to, and small thickness of, the liquefied layers. There are a number of spectacular case histories of liquefaction of sediments deposited in late Pleistocene time Q3. The clay content is not a reliable index for evaluating between clay-like and sand-like behaviors in a fine-grained soil. Fine-grained soils with the low plasticity index PI and high water content wc are susceptible to liquefaction; the use of the PI and water content to liquid limit ratio wc/LL is a good criterion of liquefaction possibility; for soils. Based on work in progress of the case histories of liquefaction and the results of laboratory tests for fine-grained soils from Boulanger, Idriss, Bray and Sancio, Seed and Cetin et al, a new liquefaction possibility criterion for soils is proposed as follows: soils with PI<12 and wc/LL>0.85 are susceptible to liquefaction; soils with 1220 or wc/LL<0.80 is not susceptible to liquefaction. |
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| Keywords: | earthquake soil liquefaction fine-grained soils plasticity index possibility of liquefaction criteria |
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