含黏粒砂土场地液化离心机振动台试验研究
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摘要
提出了含黏粒砂土模型地基制备、饱和与均匀性监测技术,利用ZJU-400土工离心机振动台开展了相同相对密度含黏粒砂土(黏粒含量10%)和洁净砂的地震液化模型试验,再现了水平场地地震液化现象,揭示了含黏粒砂土场地液化灾变特点。弯曲元波速监测表明,模型制备均匀性良好,相同条件下含黏粒砂土剪切波速比洁净砂低。而根据超静孔压消散与固结沉降观测分析发现,含黏粒砂土渗透系数比洁净砂低一个数量级,从而影响其液化前后超静孔压响应和应力应变行为。渗透性差异导致模型内超静孔压产生模式和消散速率显著不同,振动时含黏粒砂土模型浅层超静孔压累积比洁净砂慢,而深层则相反;震后含黏粒砂土孔压消散时间是洁净砂的15倍。液化过程中含黏粒砂土剪应力应变响应比相同深度处的洁净砂更显著,液化后其滞回圈应变较大、割线模量较小且阻尼比较大。土体液化沉降主要发生在液化后超静孔压消散过程,含黏粒砂土模型超静孔压消散时间更长,沉降量更大。上述成果为进一步研究含黏粒砂土地震响应分析及其液化判别提供了科学依据。
The preparation,saturation and uniformity checking methods for clayey sand ground model are proposed.Then liquefaction model tests on clayey sand with clay content of 10% are performed by means of ZJU-400 geotechnical centrifuge shaking table,and the other model for clean sand with the same relative density is also performed for comparison.Seismic liquefaction phenomena of level ground are reproduced and the liquefaction characteristics of clayey sand ground are revealed.Measuring of bender elements shows that both models are uniformly prepared,and the shear wave velocity of the clayey sand is lower than that of the clean sand under the same condition.The permeability coefficient of the clayey sand is nearly an order of magnitude lower than that of the clean sand according to the test observations,which affects the responses of the excess pore water pressure(PWP) and stress-strain relationship during liquefaction.The difference of permeability results in slower buildup of PWP in the clayey sand at shallow depth but faster one at deep depth,while the post-liquefaction dissipation is 15 times longer than that of the clean sand.Response of shear stress-strain of the clayey sand is more pronounced than that of the clean sand at the liquefaction stage,and its secant modulus is smaller and the damping ratio is larger under post-liquefaction cyclic loadings.Model settlement mainly occurs during the process of PWP dissipation,and the clayey sand has longer dissipation time and doubles the settlement of the clean sand.This study presents scientific evidence for seismic response analysis and liquefaction evaluation of clayey sand ground.
The preparation,saturation and uniformity checking methods for clayey sand ground model are proposed.Then liquefaction model tests on clayey sand with clay content of 10% are performed by means of ZJU-400 geotechnical centrifuge shaking table,and the other model for clean sand with the same relative density is also performed for comparison.Seismic liquefaction phenomena of level ground are reproduced and the liquefaction characteristics of clayey sand ground are revealed.Measuring of bender elements shows that both models are uniformly prepared,and the shear wave velocity of the clayey sand is lower than that of the clean sand under the same condition.The permeability coefficient of the clayey sand is nearly an order of magnitude lower than that of the clean sand according to the test observations,which affects the responses of the excess pore water pressure(PWP) and stress-strain relationship during liquefaction.The difference of permeability results in slower buildup of PWP in the clayey sand at shallow depth but faster one at deep depth,while the post-liquefaction dissipation is 15 times longer than that of the clean sand.Response of shear stress-strain of the clayey sand is more pronounced than that of the clean sand at the liquefaction stage,and its secant modulus is smaller and the damping ratio is larger under post-liquefaction cyclic loadings.Model settlement mainly occurs during the process of PWP dissipation,and the clayey sand has longer dissipation time and doubles the settlement of the clean sand.This study presents scientific evidence for seismic response analysis and liquefaction evaluation of clayey sand ground.
引文
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[15]KUTTER B L.Recent advances in centrifuge modeling of seismic shaking[C]//Paper No.SOA8.Proc.of the 3rd International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics Vol.II,St.Louis,Missouri,1995:927–941.
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[17]ZHOU Y G,CHEN Y M,SHAMOTO Y.Verification of the soil-type specific correlation between liquefaction resistance and shear-wave velocity of sand by dynamic centrifuge test[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2010,136(1):165–177.
[18]BRENNAN A J,THUSYANTHAN N I,MADABHUSHI S.Evaluation of shear modulus and damping in dynamic centrifuge tests[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2005,131:1488.
[19]黄春霞,张鸿儒,隋志龙,等.饱和砂土地基液化特性振动台试验研究[J].岩土工程学报,2006,28(12):2098–2103.(HUANG Chun-xia,ZHANG Hong-ru,SUI Zhi-long,et al.Shaking table tests on liquefaction properties of saturated sand groud[J].Chinese Journal of Geotechnical Engineering,2006,28(12):2098–2103.(in Chinese))
[20]龚晓南.土力学[M].北京:中国建筑工业出版社,2002:77–96.(GONG Xiao-nan.Soil mechanics[M].Beijing:China Architecture and Building Press,2002:77–96.(in Chinese))
[21]CETIN K O,YOUD T L,SEED R B,et al.Liquefaction-induced ground deformations at Hotel Sapanca during Kocaeli(Izmit),Turkey earthquake[J].Soil Dynamics and Earthquake Engineering,2002,22(9/10/11/12):1083–1092.
[22]龚晓南.高等土力学[M].杭州:浙江大学出版社,2006:229–232.(GONG Xiao-nan.Advanced soil mechanics[M].Hangzhou:Zhejiang University Press,2006:229–232.(in Chinese))
[2]石兆吉,王兰民.土壤动力特性·液化势及危害性评价[M].北京:地震出版社,1999.(SHI Zhao-ji,WANG Lan-min.Soil dynamics,liquefaction potential and hazard evaluation[M].Beijing:Earthquake Press,1999.(in Chinese))
[3]MITCHELL J K,SOGA K.Fundamentals of soil behavior[M].3rd edition.New York:John Wiley&Sons,Inc.,2005:592.
[4]汪闻韶.土液化特性中的几点发现[J].岩土工程学报,1980,2(3):55–63.(WANG Wen-shao.Some findings in soil liquefaction[J].Chinese Journal of Geotechnical Engineering,1980,2(3):55–63.(in Chinese))
[5]BRAY J D,SANCIO R B,DURGUNOGLU T,et al.Subsurface characterization at ground failure sites in Adapazari,Turkey[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2004,130(7):673–685.
[6]衡朝阳,何满潮,裘以惠.含黏粒砂土抗液化性能的试验研究[J].工程地质学报,2001,9(4):339–344.(HENG Chao-yang,HE Man-chao,QIU Yi-hui.Experimental study of liquefaction-resistant characteristics of clayey sand[J].Journal of Engineering Geology,2001,9(4):339–344.(in Chinese))
[7]刘雪珠,陈国兴.黏粒含量对南京粉细砂液化影响的试验研究[J].地震工程与工程振动,2003,23(3):150–155.(LIU Xue-zhu,CHEN Guo-xing.Experimental study on influence of clay particle content on liquefaction of Nanjing fine sand[J].Earthquake Engineering and Engineering Vibration,2003,23(3):150–155.(in Chinese))
[8]朱建群,孔令伟,钟方杰.粉粒含量对砂土强度特性的影响[J].岩土工程学报,2007,29(11):1647–1652.(ZHU Jian-qun,KONG Ling-wei,ZHONG Fang-jie.Effect of fines content on strength of silty sands[J].Chinese Journal of Geotechnical Engineering,2007,29(11):1647–1652.(in Chinese))
[9]黄茂松,曹杰.隧道地震响应简化分析与动力离心试验验证[J].岩石力学与工程学报,2010,29(2):271–280.(HANG Mao-song,CAO Jie.Simplified analysis of tunnel earthquake response and centrifuge modelling calibration[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(2):271–280.(in Chinese))
[10]苏栋,李相菘.砂土自由场地震响应的离心机试验研究[J].地震工程与工程振动,2006,26(2):166–170.(SU Dong,LI Xiang-song.Centrifuge modeling of seismic response of free sand ground[J].Earthquake Engineering and Engineering Vibration 2006,26(2):166–170.(in Chinese))
[11]刘晶波,刘祥庆,王宗纲,等.砂土地基自由场离心机振动台模型试验[J].清华大学学报,2009,49(9):31–34.(LIU Jing-bo,LIU Xiang-qing,WANG Zong-gang,et al.Dynamic centrifuge model test of an unconfined sandy foundation[J].Journal of Tsinghua University,2009,49(9):31–34.(in Chinese))
[12]李京爽,侯瑜京,徐泽平,等.砂土自由场地基水平垂直振动离心模拟试验[J].岩土力学,2011,32(增刊2):208–214.(LI Jing-shuang,HOU Yu-jing,XU Ze-ping,et al.Centrifugal modeling of seismic response of free-field sand ground under horizontal and vertical earthquakes[J].Rock and Soil Mechanics,2011,32(S2):208–214.(in Chinese))
[13]陈云敏,韩超,凌道盛,等.ZJU400离心机研制及其振动台性能评价[J].岩土工程学报,2011,32(12):1887–1894.(CHEN Yun-min,HAN Chao,LING Dao-sheng,et al.Development of geotechnical centrifuge ZJU400 and performance assessment of its shaking table system[J].Chinese Journal of Geotechnical Engineering,2011,33(12):1887–1894.(in Chinese))
[14]包承纲,饶锡保.土工离心模型的试验原理[J].长江科学院院报,1998,15(2):1–7.(BAO Cheng-gang,RAO Xi-bao.Principle of the geotechnical centrifuge model test[J].Journal of Yangtze River Scientific Research Institue,1998,15(2):1–7.(in Chinese))
[15]KUTTER B L.Recent advances in centrifuge modeling of seismic shaking[C]//Paper No.SOA8.Proc.of the 3rd International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics Vol.II,St.Louis,Missouri,1995:927–941.
[16]盛树馨,窦宜,陶秀珍,等.SL237—1999土工试验规程[S].北京:中国水利水电出版社,1999.(SHENG Shu-xin,DOU Yi,TAO Xiu-zhen,et al.SL237—1999 Specification of soil test[S].Beijing:Chian Water Power Press,1999.(in Chinese))
[17]ZHOU Y G,CHEN Y M,SHAMOTO Y.Verification of the soil-type specific correlation between liquefaction resistance and shear-wave velocity of sand by dynamic centrifuge test[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2010,136(1):165–177.
[18]BRENNAN A J,THUSYANTHAN N I,MADABHUSHI S.Evaluation of shear modulus and damping in dynamic centrifuge tests[J].Journal of Geotechnical and Geoenvironmental Engineering,ASCE,2005,131:1488.
[19]黄春霞,张鸿儒,隋志龙,等.饱和砂土地基液化特性振动台试验研究[J].岩土工程学报,2006,28(12):2098–2103.(HUANG Chun-xia,ZHANG Hong-ru,SUI Zhi-long,et al.Shaking table tests on liquefaction properties of saturated sand groud[J].Chinese Journal of Geotechnical Engineering,2006,28(12):2098–2103.(in Chinese))
[20]龚晓南.土力学[M].北京:中国建筑工业出版社,2002:77–96.(GONG Xiao-nan.Soil mechanics[M].Beijing:China Architecture and Building Press,2002:77–96.(in Chinese))
[21]CETIN K O,YOUD T L,SEED R B,et al.Liquefaction-induced ground deformations at Hotel Sapanca during Kocaeli(Izmit),Turkey earthquake[J].Soil Dynamics and Earthquake Engineering,2002,22(9/10/11/12):1083–1092.
[22]龚晓南.高等土力学[M].杭州:浙江大学出版社,2006:229–232.(GONG Xiao-nan.Advanced soil mechanics[M].Hangzhou:Zhejiang University Press,2006:229–232.(in Chinese))
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