| 汶川地震砾性土液化场地特征解析 |
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| 引用本文： | 袁晓铭,王海,曹振中,徐鸿轩.汶川地震砾性土液化场地特征解析[J].地球物理学报,2017,60(7):2733-2743. |
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| 作者姓名： | 袁晓铭 王海 曹振中 徐鸿轩 |
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| 作者单位： | 1. 中国地震局工程力学研究所, 中国地震局地震工程与工程振动重点实验室, 哈尔滨 150080;2. 桂林理工大学, 桂林 541004 |
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| 基金项目： | 中央级公益性研究所基本科研业务费专项（2016A02），广西自然科学基金项目（2014GXNSFBA118257，2016GXNSFAA380117）和国家自然科学基金（51278472，41272357，51669005）资助. |
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| 摘 要： | 通过成都平原砾性土场地勘察测试,研究汶川地震中大量砾性土液化场地的基本特性,找出一般规律,对砾性土场地液化发生主客观原因提出解释,并修正以往若干认识偏差.分析表明:汶川地震液化砾性土层粒径范围宽,含砾量5%~85%甚至更大,同时其实测剪切波速140~270 m·s~(-1),修正剪切波速160~314 m·s~(-1),都远超历史记录;液化砾性土场地1/2集中在Ⅷ度区内,表明如砂土层液化一样,砾性土场地大规模液化需要较强地震动触发,但超过触发强度后液化规模增长均有限;成都平原浅表地层二元基本结构是汶川地震中出现大量砾性土场地的客观条件之一,该结构可使饱和砾性土层处于封闭状态,构成了砾性土液化的基本条件;虽然液化砾性土层剪切波速很高,但实际上大多松散状态,是此次地震大量砾性土场地发生液化的客观条件之二;地震中地表(井中)喷出物与地下实际液化土类大相径庭,且液化层埋深大多小于6.0 m,以往以地表喷出物反推地下液化层土性类型的做法不再成立;认为砾性土层波速大、透水性好而不会液化的传统认识也不再成立,但砾性土层液化条件与砂土层液化条件不同,前者要求更高.
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| 关 键 词： | 砾性土液化 场地特性 汶川地震 PGA 含砾量 剪切波速 |
| 收稿时间： | 2016-08-15 |
Interpretation to characteristics of gravelly soils sites that liquefied in Wenchuan earthquake |
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| YUAN Xiao-Ming,WANG Hai,CAO Zhen-Zhong,XU Hong-Xuan.Interpretation to characteristics of gravelly soils sites that liquefied in Wenchuan earthquake[J].Chinese Journal of Geophysics,2017,60(7):2733-2743. |
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| Authors: | YUAN Xiao-Ming WANG Hai CAO Zhen-Zhong XU Hong-Xuan |
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| Institution: | 1. Institution of Engineering Mechanics, China Earthquake Administration, Key Laboratory of Earthquake Engineering and Engineering Vibration of China Earthquake Administration, Harbin 150080, China;2. Guilin University of Technology, Guangxi Guilin 541004, China |
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| Abstract: | Through field tests at the gravelly soils sites in Chengdu plain, the characteristics of the massive liquefied gravelly soils sites in Wenchuan earthquake are studied and the general rules governing the liquefaction behaviors are proposed. New interpretations on the conditions of gravelly soils liquefaction are obtained that some previous misunderstandings are corrected. The analysis indicates:the ranges of particle diameters of the liquefied gravelly soils are wide that the gravel contents vary from 5% to 85% or even beyond; the tested shear-wave velocity is 140 m·s-1 to 270 m·s-1 and then corrected as 160 m·s-1 to 314 m·s-1, exceeding the previously recorded; one half of the gravelly liquefied sites are located in seismic intensity Ⅷ (Chinese Scale) regions, i.e., like sand liquefaction to trigger massive gravelly soils liquefaction requires intense ground shaking; however, the scale of gravelly soils liquefaction can only limitedly increase when the ground shaking triggers liquefaction; the dual-structural soil at shallow depth in Chengdu plain consists of gravelly soils layers and overburden soil layers, i.e., the first of the conditions for gravelly soils liquefaction; the overburden soil layers seal the saturated gravelly soils layers, forming a fundamental condition of liquefaction for gravelly soils; the shear-wave velocity of gravelly soils is large yet the most gravels stay actually very loose, i.e., the second essential condition for the massive gravelly soils liquefaction; the surface ejecta during the earthquake are quite different from the actual liquefied soils which lie less than 6 m in depth that judging from the surface ejecta to deduce the underground liquefied soil categories is not appropriate anymore; the traditional senses that gravelly soils is not liquefiable because of its large shear-wave velocity and large permeability cannot hold; the liquefaction conditions of gravelly soils and general sandy soils are different, since the requirements for the former are considerably stringent. |
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| Keywords: | Gravelly soils liquefaction Site characteristics Wenchuan Earthquake PGA Gravel content Shear wave velocity |
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