下蜀土边坡地震稳定性的大型振动台试验研究(Ⅰ)——模型试验设计
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摘要
为研究下蜀土边坡的地震稳定性,选用天然下蜀土,按照Meymand的相似法则,对一坡高为0.5m、宽度为1.05m、坡角为45°的模型边坡进行了几何相似常数为20的1g大型振动台模型试验详细设计。首先,运用数值模拟的方法确定了模型边坡尺寸适当的边界范围,模型边坡地基厚度、坡脚前缘和坡肩后缘长度均取为0.5m;其次,按照确定的模型几何尺寸设计了符合试验要求的模型箱,其内壁净尺寸(长×宽×高)为1500mm×1050mm×1100mm,属刚性模型箱,且不会与模型边坡发生共振;最后,制定了包括加速度和位移在内的数据量测策略,运用拟静力法求得下蜀土边坡平均屈服加速度为0.561g,综合确定了地震动峰值(PGA)按0.1g、0.3g、0.6g和0.9g的顺序逐级加载的原则,并制定了详细的试验步骤,从而可保障试验得到可靠的结果。
Using natural Xiashu loesses and applying the law of similitude after Meymand,a detailed design of a 1g large-scale shaking table model test with a similarity factor of 20 for a model slope with a height of 0.5m,width of 1.05m,and slope angle of 45°was carried out aiming at investigating the seismic stability of Xiashu loess slopes.Firstly,appropriate boundary range of the model slope with a depth of the model slope base,a distance from the model slope toe to the left slope boundary and the one from the model slope crest to the right slope boundary all of 0.5m was identified by means of numerical analysis;Secondly, a rigid model box,which had internal dimensions of 1050 mm by 1500 mm in size and 1100 mm in height according to the determined dimension of the model slope was designed well meeting the requirements of the test and would not cause resonance with the model slope;Finally,tactics of measurements including accelerations and displacements were established,the average critical acceleration of the model slope of 0.561g was determined using the pseudostatic method,a series of loading rules were comprehensively identified in terms of the sequences of the peak ground acceleration(PGA) of 0.1g,0.3g,0.6g and 0.9g,and detailed test procedures were established,which gave a powerful guarantee for the test.
Using natural Xiashu loesses and applying the law of similitude after Meymand,a detailed design of a 1g large-scale shaking table model test with a similarity factor of 20 for a model slope with a height of 0.5m,width of 1.05m,and slope angle of 45°was carried out aiming at investigating the seismic stability of Xiashu loess slopes.Firstly,appropriate boundary range of the model slope with a depth of the model slope base,a distance from the model slope toe to the left slope boundary and the one from the model slope crest to the right slope boundary all of 0.5m was identified by means of numerical analysis;Secondly, a rigid model box,which had internal dimensions of 1050 mm by 1500 mm in size and 1100 mm in height according to the determined dimension of the model slope was designed well meeting the requirements of the test and would not cause resonance with the model slope;Finally,tactics of measurements including accelerations and displacements were established,the average critical acceleration of the model slope of 0.561g was determined using the pseudostatic method,a series of loading rules were comprehensively identified in terms of the sequences of the peak ground acceleration(PGA) of 0.1g,0.3g,0.6g and 0.9g,and detailed test procedures were established,which gave a powerful guarantee for the test.
引文
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[2]沈建,陈新民,魏平.土质边坡地震稳定性研究进展[J].水运工程,2009,(6):40-46. Shen J,Chen X M,Wei P.Review on the study of seismic stability of soil slopes[J].Port & Waterway Engineering,2009,(6):40-46.
[3]Bray J D,Travasarou T.Simplified procedure for estimating earthquake-induced deviatoric slope displacements [J].Journal of Geotechnical and Geoenviron-mental Engineering,2007,133(4):381-392.
[4]Kramer S L,Lindwall N W.Dimensionality and directionality effects in Newmark sliding block analyses [J].Journal of Geotechnical and Geoenvironmental Engineering,2004,130(3):303-315.
[5]Stewart J P,Blake T F,Hollingsworth R A.A screen analysis procedure for seismic slope stability [J].Earthquake Spectra,2003,19(3):697-712.
[6]Rathje E M,Bray J D.An examination of simplified earthquake-induced displacement procedures for earth structures[J].Canadian Geotechnical Journal,1999. 36(1):72-87.
[7]Bray J D,Rathje E M.Earthquake-induced displacements of solid-waste landfills[J].Journal of Geotechnical and Geoenvironmental Engineering,1998,124 (3):242-253.
[8]Prasad S K,Towhata I,Chandradhara G P,et al. Shaking table tests in earthquake geotechnical engineering [J].Current Science,2004,87(10):1398- 1404.
[9]Wartman J,Bray J D,Seed R B.Inclined plane studies of the Newmark sliding block procedure[J].Journal of Geotechnical and Geoenvironmental Engineering, 2003,129(8):673-684.
[10]Wartman J,Seed R B,Bray J D.Shaking table modeling of seismically induced deformations in slopes[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2005,131(5):610-622.
[11]Chen W Y,Bray J D,Seed R B.Shaking table model experiments to assess seismic slope deformation analysis procedures[C]//Proceedings of the 8th US National Conference of Earthquake Engineering,100th Anniversary Earthquake Conference Commemorating the 1906 San Francisco Earthquake,Oakland,CA: EERI,2006.
[12]Lin M L,Wang K L.Seismic slope behavior in a large-scale shaking table model test[J].Engineering Geology,2006,(86):118-133.
[13]徐光兴,姚令侃,李朝红,等.边坡地震动力响应规律及地震动参数影响研究[J].岩土工程学报,2008,30(6): 918-923. Xu G X,Yao L K,Li Z H,et al.Dynamic response of slopes under earthquakes and influence of ground motion parameters[J].Chinese Journal of Geotechnical Engineering,2008,30(6):918-923.
[14]徐光兴,姚令侃,高召宁,等.边坡动力特性与动力响应的大型振动台模型试验研究[J].岩石力学与工程学报,2008,27(3):624-632. Xu G X,Yao L K,Gao Z N,et al.Large-scale shaking table model test study on dynamic characteristics and dynamic responses of slope[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(3):624- 632.
[15]Meymand P J.Shaking table scale model tests of nonlinear soil-pile-superstructure interaction in soft clay [D].Berkeley,Calf.:U.C.Berkeley,1998.
[16]Chen W Y.Physical model studies of seismic slope response and performance[D].Berkeley,Calf.:U.C. Berkeley,2004.
[17]殷宗泽,等.土工原理[M].北京:中国水利水电出版社,2007.
[18]杨旭东.振动台模型试验若干问题的研究[D].北京:中国建筑科学研究院,2005. Yang X D.The studying of some problems in shaking table model test[D].Beijing:China Academy of Building Research,2005.
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