砾性土液化特性与机理

曹振中; 刘荟达; 袁晓铭

doi:10.11779/CJGE201607001

砾性土液化特性与机理 English Version

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,黑龙江哈尔滨 150080

基金项目: 中国地震局工程力学研究所基本科研业务费专项资助项目（2016B01）；国家自然科学基金项目（51208477,41272357）

详细信息

作者简介:
曹振中(1982- ),男,博士,副研究员,主要从事岩土地震工程方面的研究。E-mail: iemczz@163.com。

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出版历程
- 收稿日期: 2015-08-23
- 发布日期: 2016-07-24

Liquefaction characteristics and mechanism of gravelly soils

Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China

摘要

摘要: 2008年汶川地震之前,全球历史地震中砾性土液化实例不足10例,远远少于砂土液化的数量和规模,实际地震中砾性土液化的发生较为罕见,必然存在较为严格的发生条件,在土性条件、地震荷载、埋藏条件等均满足时才有可能发生。以2008年汶川地震大量砾性土液化为背景,详细分析了砾性土液化实例的水文与工程地质条件、渗透性能与排水边界条件,选取了典型砾性土液化场地并人工探坑获取砾性土试样,开展了试样直径为150 mm的动三轴和振动台对比试验。结果表明：①橡皮膜嵌入效应可以忽略或者进行有效消除后,相同相对密实度下砾性土、砂土的抗液化强度较为接近;②采用Seed等的孔压计算模型,随着动应力水平的逐渐增大,归一化的砾性土残余孔压比向上突起,增长模型趋向于A型曲线;③全球其他历史地震和2008年汶川地震砾性土液化实例中,基本上存在砾性土渗透系数较低或者排水边界条件受阻的情况;④砾性土符合无黏性散粒土体（包括砂土）发生液化的一般机理解释,但是,砾性土产生孔隙水压力上升、有效应力下降的现象,需要具备两个必要条件：①振动作用足以使砾性土的结构发生破坏而振密或土颗粒压碎,产生的剪应变只有大于门槛剪应变时（约0.02%）,孔压才会进一步发展,剪应变只有大于一定程度时（约0.1%）,孔压才有可能迅速增长直至达到上覆压力;②只有在不排水条件或排水通道不畅通的条件下,砾性土场地才有可能发生液化。
- 砾性土液化 /
- 抗液化强度 /
- 孔压模型 /
- 排水条件 /
- 机理
Abstract: Liquefaction of gravelly soils is an unusual phenomenon during earthquake. Not more than 10 case histories are reported before “2008 Wenchuan earthquake”. The occurrence of gravelly soils has to meet strict conditions, including property of soils, intensity of earthquake shaking and burial conditions. Based on widespread liquefaction of gravelly soils during “2008 Wenchuan earthquake”, the hydraulic and geological background, permeability and drainage conditions of liquefied sites of gravelly soils are analyzed, and a typical case is selected to trench, and gravelly samples at liquefied layer are collected for shaking table tests and triaxial tests on specimens with diameter of 150 mm. The results reveal: (1) If the effect of membrane compliance is eliminated or neglected, the liquefaction resistance of gravelly soils is about identical to that of sand. (2) Using the pore water pressure model of Seed (1976), the normalized accumulative pore water pressure bulges up with the increasing level of cyclic stress. (3) For the reported case histories and liquefied situations during “2008 Wenchuan earthquake”, the drainage pass is almost clogged or the permeability of liquefied layer is low. (4) The increasing pore water pressure of loose gravelly soils and the decreasing effective stress under load of cyclic stress have two basic requirements. One is that the level of cyclic stress should be high enough to crush the soil particles or to destruct the structure of soil particles so that the gravelly soils become denser. As shear strain is up to the threshold strain of 0.02%, the pore water pressure begins to be generated, until the shear strain is greater than 0.1%, and the pore water pressure develops quickly even up to the total pressure. The other is that the drainage pass should be clogged or the permeability is low.
- gravelly soil liquefaction /
- liquefaction resistance /
- pore water pressure model /
- drainage condition /
- mechanism

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参考文献(32)

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