循环荷载下饱和南沙珊瑚砂的液化特性试验研究
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摘要
针对饱和南沙岛礁珊瑚砂,开展了一系列不排水循环加载试验,研究了相对密度D_r和初始围压■对饱和珊瑚砂的超孔隙水压力、应变发展、有效应力路径及动强度特性的影响,并比较了珊瑚砂与福建砂的液化特性差异。试验表明,珊瑚砂的超静孔压Δu的发展模式与石英砂的有较大区别,可用修正后的Seed模型进行表征。珊瑚砂液化时的累积能量耗散远比福建砂的大。珊瑚砂的轴向应变ε_(DA)随着循环振次增加而逐渐变大,不会发生急剧增大的现象。在有效应力路径接触相转换线后,珊瑚砂会发生剪胀和剪缩交替出现的现象,仍然会存在有效应力。较之福建砂Δu的波动特征,珊瑚砂Δu的波动更大,且当Δu接近■时波动明显增大,产生"瞬时液化"现象。珊瑚砂的动强度随着D_r以及■的增大而增大。珊瑚砂的动强度大于石英砂的动强度。
Undrained cyclic traxial tests are carried out on the saturated coral sand in Nansha Islands,South China Sea.The experiment aims at investigating the characteristics of pore water pressure,axial strain,effective stress path and cyclic resistance of coral sand under different D_r and ■.The differences between coral sand and Fujian sand about liquefaction characteristic are also discussed.The test results indicate that the development of pore water pressure(Δu) of coral sand is different from that of siliceous sand,which can be fitted by a modified Seed model.The accumulative energy dissipation of liquefied coral sand is greater than that of liquefied Fujian sand.The axial strain(ε_(DA)) of coral sand has no sudden enlargement phenomenon during cyclic loading,and the amplitude of ε_(DA) increases continuingly with the loading time.When touching the phase transformation line,the coral sand shows the alternation of dilatancy and contraction as the effective stress still exists.Compared with the Fujian sand,the coral sand has a greater fluctuation in especially when approaching ■,and a phenomenon of transient liquefaction can be observed in the tests.The cyclic resistance of coral sand increases with the increase of D_r and ■.The cyclic resistance of coral sand is basically higher than that of siliceous sand.
Undrained cyclic traxial tests are carried out on the saturated coral sand in Nansha Islands,South China Sea.The experiment aims at investigating the characteristics of pore water pressure,axial strain,effective stress path and cyclic resistance of coral sand under different D_r and ■.The differences between coral sand and Fujian sand about liquefaction characteristic are also discussed.The test results indicate that the development of pore water pressure(Δu) of coral sand is different from that of siliceous sand,which can be fitted by a modified Seed model.The accumulative energy dissipation of liquefied coral sand is greater than that of liquefied Fujian sand.The axial strain(ε_(DA)) of coral sand has no sudden enlargement phenomenon during cyclic loading,and the amplitude of ε_(DA) increases continuingly with the loading time.When touching the phase transformation line,the coral sand shows the alternation of dilatancy and contraction as the effective stress still exists.Compared with the Fujian sand,the coral sand has a greater fluctuation in especially when approaching ■,and a phenomenon of transient liquefaction can be observed in the tests.The cyclic resistance of coral sand increases with the increase of D_r and ■.The cyclic resistance of coral sand is basically higher than that of siliceous sand.
引文
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[3]CELESTINO T B,MITCHELL J K.Behavior of carbonate sands for foundations of offshore structures[C]//Proceedings of Brazil Offshore'83,Rio de janeiro,1983:85-102.
[4]MEJIA L H,YEUNG M R.Liquefaction of Coralline Soils during the 1993 guam earthquake[C]//Earthquake-induced Movements and Seismic Remediation of Existing Foundations and Abutments:Proceedings of Sessions Held in Conjunction with the ASCE Convention in San Diego.San Diego,1995:33-48.
[5]CHOCK G,KINDRED T,ROBERTSON I,et al.Compilation of observations of the October 15,2006 Kiholo bay(Mw 6.7)and Mahukona(Mw 6.0)Earthquakes,Hawai'i[R].Earthquake Engineering Research Institute(EERT).http://www.eeri.org/2006/10/island-of-hawaii/.2006.
[6]OLSON S M,GREEN R A,LASLEY S,et al.Documenting liquefaction and lateral spreading triggered by the 12 January2010 haiti earthquake[J].Earthquake Spectra,2012,27(S1):S93-S116.
[7]HYODO M,HYDE A F L,ARAMAKI N.Liquefaction of crushable soils[J].Géotechnique,1998,48(4):527-543.
[8]SALEM M,ELMAMLOUK H,AGAIBY S.Static and cyclic behavior of North Coast calcareous sand in Egypt[J].Soil Dynamics and Earthquake Engineering,2013,55:83-91.
[9]SHARMA S S,ISMAIL M A.Monotonic and cyclic behavior of two calcareous soils of different origins[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(12):1581-1591.
[10]虞海珍,汪稔.钙质砂动强度试验研究[J].岩土力学,1999,20(4):6-11.(YU Hai-zhen,WANG Ren.Experimental study on dynamic strength of calcareous sand[J].Rock and Soil Mechanics,1999,20(4):6-11.(in Chinese))
[11]李建国.波浪荷载作用下饱和钙质砂动力特性的试验研究[D].武汉:中国科学院武汉岩土力学研究所,2005.(LIJian-guo.Experimental research on dynamic behavior of saturated calcareous sand under wave loading[D].Wuhan:Institute of Rock&Soil Mechanics Chinese Academy of Sciences.P.R.China,2005.(in Chinese))
[12]FIGUEROA J L,SAADA A S,LIANG L,et al.Evaluation of soil liquefaction by energy principles[J].Journal of Geotechnical Engineering,1994,120(9):1554-1569.
[13]LEE K L,ALBAISA A.Earthquake induced settlements in saturated sands[J].Journal of the Geotechnical Engineering Division,1974,100(4):387-406.
[14]SEED H B,LYSMER J,MARTIN P P.Pore-water pressure changes during soil liquefaction[J].Journal of the Geotechnical Engineering,1976,102(4):323-346.
[15]BOOKER J R,RAHMAN M S,SEED H B.GADFLEA-Acomputer program for the analysis of pore pressure generation and dissipation during cyclic or earthquake loading[R].Berkeley:Earthquake Engineering Research Center,Univ of California at Berkeley,1976.
[16]SEED H B,TOKIMATSU K,HARDER L F,et al.Influence of SPT procedures in soil liquefaction resistance evaluations[J].Journal of Geotechnical Engineering,1985,111(12):1425-1445.
[17]MARTIN G R,FINN W D L,SEED H B.Fundamentals of liquefaction under cyclic loading[J].Journal of the Geotechnical Engineering,1975,101(5):423-438.
[18]BRANDES H G.Simple shear behavior of calcareous and quartz sands[J].Geotechnical&Geological Engineering,2011,29(1):113-126.
[19]SANDOVAL E A,PANDO M A.Experimental assessment of the liquefaction resistance of calcareous biogenous sands[J].Earth Sciences Research Journal,2012,16(16):55-63.
[20]LAVIELLE T H.Liquefaction susceptibility of uncemented calcareous sands from Puerto Rico by cyclic triaxial testing[D].Montgomery County:Virginia Tech,2008.