砂砾土液化的剪切波速判别方法
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摘要
剪切波速也正逐步成为土层液化判别的基本指标之一,但采用现场波速资料得到的砂砾土液化判别方法尚较少见。针对2008年汶川8.0级地震显著的砂砾土液化现象,获取45个场地剪切波速结构,以此提出基于剪切波速的砂砾土液化判别方法;构建相应模型和计算公式,并分析现有2种典型砂土液化剪切波速判别方法对砂砾土的适用性。提出的砂砾土液化剪切波速判别方法由初判和复判组成,初判包括地质年代、埋藏条件和含砾量3个条件;复判模型则由地震烈度、剪切波速基准值、地下水位、砂砾土埋深和和含砾量等5个参数构成,并分别采用归一化方法和优化方法推导出剪切波速基准值以及地下水位和砂砾土埋深的影响系数。砂砾土与砂土属不同土类,相同波速值下二者密实程度不同,现有砂土液化剪切波速判别方法对砂砾土不适用,给出的判别结果明显偏于危险。获取的砂砾土液化资料扩充现有液化数据库内容,提出的砂砾土液化剪切波速判别方法简单明了,回判成功率高,可为工程应用及规范修订提供参考。
Although the in-situ shear wave velocity tests have been used commonly as engineering testing techniques and shear wave velocity Vs has gradually become a basic index for soil liquefaction evaluation,the in-situ Vs-based liquefaction assessment methods for gravel soils are not available so far. The significant phenomena of gravelly soil liquefaction in the 2008 Wenchuan 8.0 Earthquake are investigated and the in-situ Vs structures for 45 sites in the event are obtained. In terms of the investigation data,the Vs-based approach for liquefaction evaluation of gravel soils is presented and the existing Vs-based methods for evaluating sandy soil liquefaction are inspected. The liquefaction discrimination of gravel soils can be divided into the two steps:the preliminary evaluation and further evaluation. In the preliminary step the geological ages,the buried condition of gravel soil layer and gravel contents of gravel soils are considered and five parameters including seismic intensity,reference values of Vs with depth of gravel soils,groundwater table and gravel content of gravel soils are concerned in the further step. The reference values of Vs as well as the influential coefficients of gravel soil depths and groundwater levels are deduced by normalization method and optimization method respectively. As the type of gravel soils differs from the sandy soils,the densities of two type soils even for the same Vs value are different. If the existing liquefaction assessment procedures for sandy soils are employed,the liquefaction resistance ofgravel soils will be significantly overestimated,which means that the methods of liquefaction evaluation for sandy soils are not suitable for gravel soils. The proposed method is noticed with clear expression and high success ratio of regression discrimination;and it can easily be used in engineering practice and code revision.
Although the in-situ shear wave velocity tests have been used commonly as engineering testing techniques and shear wave velocity Vs has gradually become a basic index for soil liquefaction evaluation,the in-situ Vs-based liquefaction assessment methods for gravel soils are not available so far. The significant phenomena of gravelly soil liquefaction in the 2008 Wenchuan 8.0 Earthquake are investigated and the in-situ Vs structures for 45 sites in the event are obtained. In terms of the investigation data,the Vs-based approach for liquefaction evaluation of gravel soils is presented and the existing Vs-based methods for evaluating sandy soil liquefaction are inspected. The liquefaction discrimination of gravel soils can be divided into the two steps:the preliminary evaluation and further evaluation. In the preliminary step the geological ages,the buried condition of gravel soil layer and gravel contents of gravel soils are considered and five parameters including seismic intensity,reference values of Vs with depth of gravel soils,groundwater table and gravel content of gravel soils are concerned in the further step. The reference values of Vs as well as the influential coefficients of gravel soil depths and groundwater levels are deduced by normalization method and optimization method respectively. As the type of gravel soils differs from the sandy soils,the densities of two type soils even for the same Vs value are different. If the existing liquefaction assessment procedures for sandy soils are employed,the liquefaction resistance ofgravel soils will be significantly overestimated,which means that the methods of liquefaction evaluation for sandy soils are not suitable for gravel soils. The proposed method is noticed with clear expression and high success ratio of regression discrimination;and it can easily be used in engineering practice and code revision.
引文
[1]SEED H B.Soil liquefaction and cyclic mobility evaluation for level ground during earthquakes[J].Journal of Geotechnical Engineering Division,1979,105(GT2):201–255.
[2]YOUD T L,IDRISS I M.Proceedings of the NCEER workshop on evaluation of liquefaction resistance of soils[R].Buffalo,NY:NCEER–97–0022,1997.
[3]SEED R B,MOSS R E S,KAMMERER A M,et al.Recent advances in soil liquefaction engineering,a unified and consistent framework[R].EERC,USA:Earthquake Engineering Research Center,2003.
[4]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 Wenshao.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))
[5]COX B R.Development of a direct test method for dynamically assessing the liquefaction resistance of soils in situ[Ph.D.Thesis][D].Austin:University of Texas at Austin,2006.
[6]汪闻韶.土工地震减灾工程中的一个重要参量——剪切波速[J].水利学报,1994,(3):80–84.(WANG Wenshao.An important parameter in geotechnical engineering for earthquake disaster mitigation—shear wave velocity[J].Journal of Hydraulic Engineering,1994,(3):80–84.(in Chinese))
[7]石兆吉,郁寿松,丰万玲.土壤液化式的剪切波速判别方法[J].岩土工程学报,1993,15(1):74–80.(SHI Zhaoji,YU Shousong,FENG Wanling.Shear wave velocity based soil liquefaction evaluation[J].Chinese Journal of Geotechnical Engineering,1993,15(1):74–80.(in Chinese))
[8]ANDRUS R D,STOKOE K H.Liquefaction resistance of soils from shear-wave velocity[J].Journal of Geotechnical and Geoenvironmental Engineering,2000,126(11):1015–1025.
[9]刘惠珊.砾石的液化判别探讨[C]//第五届全国地震工程学术会议论文.北京:[s.n].,1998:183–188.(LIU Huishan.Gravel soils liquefaction evaluation discuss[C]//Proceedings of the5th National Earthquake Engineering Symposium.Beijing:[s.n].,1998:183–188.(in Chinese))
[10]YOUD T L,IDRISS I M.Liquefaction resistance of soils:summary report from the1996NCEER and1998NCEER/NSF workshops on evaluation of liquefaction resistance of soils[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(4):297–313.
[11]袁晓铭,曹振中,孙锐,等.汶川8.0级地震液化特征初步研究[J].岩石力学与工程学报,2009,28(6):1288–1296.(YUAN Xiaoming,CAO Zhenzhong,SUN Rui,et al.Preliminary research on liquefaction characteristics of Wenchuan8.0earthquake[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(6):1288–1296.(in Chinese))
[12]何银武.论成都盆地的成生时代及其早期沉积物的一般特征[J].地质论评,1992,38(2):149–156.(HE Yinwu.The ages of formation of Chengdu basin and features of its early deposits[J].Geological Review,1992,38(2):149–156.(in Chinese))
[13]《工程地质手册》编辑委员会.工程地质手册[M].3版.北京:中国建筑工业出版社,1992.(Engineering Geology Manual Compilation Group.Engineering geology manual[M].3rd ed.Beijing:China Architecture and Building Press,1992.(in Chinese))
[14]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.GB0011–2001Code for seismic design of buildings[S].Beijing:China Architecture and Building Press,2001.(in Chinese))
[15]SYKORA D W.Creation of a data base of seismic shear wave velocities for correlation analysis[R].Vicksburg,MI:GL–87–26,1987.
[16]王昆耀,常亚屏,陈宁.饱和砂砾料液化特性的试验研究[J].水利学报,2000,(2):37–41.(WANG Kunyao,CHANG Yaping,CHEN Ning.Experimental study of liquefaction characteristics of saturated sandy gravel[J].Journal of Hydraulic Engineering,2000,(2):37–41.(in Chinese))
[17]SUZUKI Y,GOTO S,HATANAKA M,et al.Correlation between strength and penetration resistances for gravel soils[J].Soils and Foundations,1993,33(1):92–101.
[18]EVANS M D,ZHOU S P.Liquefaction behavior of sand-gravel composites[J].Journal of Geotechnical Engineering,1995,121(3):287–298.
[2]YOUD T L,IDRISS I M.Proceedings of the NCEER workshop on evaluation of liquefaction resistance of soils[R].Buffalo,NY:NCEER–97–0022,1997.
[3]SEED R B,MOSS R E S,KAMMERER A M,et al.Recent advances in soil liquefaction engineering,a unified and consistent framework[R].EERC,USA:Earthquake Engineering Research Center,2003.
[4]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 Wenshao.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))
[5]COX B R.Development of a direct test method for dynamically assessing the liquefaction resistance of soils in situ[Ph.D.Thesis][D].Austin:University of Texas at Austin,2006.
[6]汪闻韶.土工地震减灾工程中的一个重要参量——剪切波速[J].水利学报,1994,(3):80–84.(WANG Wenshao.An important parameter in geotechnical engineering for earthquake disaster mitigation—shear wave velocity[J].Journal of Hydraulic Engineering,1994,(3):80–84.(in Chinese))
[7]石兆吉,郁寿松,丰万玲.土壤液化式的剪切波速判别方法[J].岩土工程学报,1993,15(1):74–80.(SHI Zhaoji,YU Shousong,FENG Wanling.Shear wave velocity based soil liquefaction evaluation[J].Chinese Journal of Geotechnical Engineering,1993,15(1):74–80.(in Chinese))
[8]ANDRUS R D,STOKOE K H.Liquefaction resistance of soils from shear-wave velocity[J].Journal of Geotechnical and Geoenvironmental Engineering,2000,126(11):1015–1025.
[9]刘惠珊.砾石的液化判别探讨[C]//第五届全国地震工程学术会议论文.北京:[s.n].,1998:183–188.(LIU Huishan.Gravel soils liquefaction evaluation discuss[C]//Proceedings of the5th National Earthquake Engineering Symposium.Beijing:[s.n].,1998:183–188.(in Chinese))
[10]YOUD T L,IDRISS I M.Liquefaction resistance of soils:summary report from the1996NCEER and1998NCEER/NSF workshops on evaluation of liquefaction resistance of soils[J].Journal of Geotechnical and Geoenvironmental Engineering,2001,127(4):297–313.
[11]袁晓铭,曹振中,孙锐,等.汶川8.0级地震液化特征初步研究[J].岩石力学与工程学报,2009,28(6):1288–1296.(YUAN Xiaoming,CAO Zhenzhong,SUN Rui,et al.Preliminary research on liquefaction characteristics of Wenchuan8.0earthquake[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(6):1288–1296.(in Chinese))
[12]何银武.论成都盆地的成生时代及其早期沉积物的一般特征[J].地质论评,1992,38(2):149–156.(HE Yinwu.The ages of formation of Chengdu basin and features of its early deposits[J].Geological Review,1992,38(2):149–156.(in Chinese))
[13]《工程地质手册》编辑委员会.工程地质手册[M].3版.北京:中国建筑工业出版社,1992.(Engineering Geology Manual Compilation Group.Engineering geology manual[M].3rd ed.Beijing:China Architecture and Building Press,1992.(in Chinese))
[14]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.GB0011–2001Code for seismic design of buildings[S].Beijing:China Architecture and Building Press,2001.(in Chinese))
[15]SYKORA D W.Creation of a data base of seismic shear wave velocities for correlation analysis[R].Vicksburg,MI:GL–87–26,1987.
[16]王昆耀,常亚屏,陈宁.饱和砂砾料液化特性的试验研究[J].水利学报,2000,(2):37–41.(WANG Kunyao,CHANG Yaping,CHEN Ning.Experimental study of liquefaction characteristics of saturated sandy gravel[J].Journal of Hydraulic Engineering,2000,(2):37–41.(in Chinese))
[17]SUZUKI Y,GOTO S,HATANAKA M,et al.Correlation between strength and penetration resistances for gravel soils[J].Soils and Foundations,1993,33(1):92–101.
[18]EVANS M D,ZHOU S P.Liquefaction behavior of sand-gravel composites[J].Journal of Geotechnical Engineering,1995,121(3):287–298.
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