波浪荷载下饱和粉土不排水动力特性试验研究
|
摘要
确保海床场地的动力稳定性是近海工程安全运行的前提。目前针对复杂应力路径对海域环境饱和粉土动力学行为特性的影响研究尚属少见。利用GDS空心圆柱扭剪仪,开展了轴向-扭转耦合循环加载的重塑饱和粉土不排水试验,模拟波浪的波幅大小和海床深度变化,以广义剪应变γ_g=5%为液化标准,研究了均等固结条件下循环应力路径(循环应力比CSR和循环加载幅值比δ)对饱和粉土不排水动力特性的影响。结果表明:CSR与δ值的大小对饱和粉土的超静孔压与变形发展特性影响显著,圆形应力路径(δ=1)循环加载时饱和粉土最易液化;当CSR≤0.050时,饱和粉土不会发生液化;当CSR≥0.065且δ=1时,饱和粉土会发生液化;CSR> 0.150时,粉土易发生液化。γ_g与孔压比r_u的相关性受CSR与δ值大小的影响较小,且γ_g可表示以r_u为变量的正切函数。以等效循环应力比ESR作为表征复杂应力路径下动应力大小的指标,饱和粉土达到γ_g=5%所需的液化振次N_L与施加的ESR值具有事实上的唯一性关系,ESR随N_L的增大而减小。
To ensure the dynamic stability of seabed site is the prerequisite for the safe operation of offshore engineering. However, limited test data on the dynamic properties of saturated silt subjected to cyclic loading with complex stress path in marine environment are available. Using the GDS hollow cylinder apparatus, a series of undrained tests is performed on the remolded saturated silt under combined axial-torsional cyclic loading for simulating changes in the amplitude of the wave and the depth of seabed. To take the generalized shear strain γ_g = 5% as the liquefaction triggering criteria, the influences of cyclic stress paths(cyclic stress ratio CSR and cyclic loading amplitude ratio δ) on the undrained behavior of saturated silt under isotropic consolidation conditions are studied. The test results show that the effects of CSR and δ on the development patterns of excess pore pressure and deformation of saturated silt are significant. The saturated silt under the cyclic loading with circular stress path(δ= 1) is the most susceptible to liquefaction. The liquefaction of saturated silt is not triggered when CSR≤ 0.050, but when CSR≥ 0.065 and δ= 1, the liquefaction of saturated silt can be triggered, and the saturated silt is more susceptible to liquefaction when CSR > 0.150. The correlation between γ_g and excess pore pressure ratio(r_u) is less influenced by CSR and δ, and the γ_g can be characterized by the tangent function of r_u. When the equivalent cyclic stress ratio ESR is uesd as the index of the amplitude of cyclic stress with complex stress paths, the liquefaction number of cycles(N_L) required to cause γ_g = 5% may be uniquely correlated to the applied ESR, and the ESR decreases with the increase of N_L.
To ensure the dynamic stability of seabed site is the prerequisite for the safe operation of offshore engineering. However, limited test data on the dynamic properties of saturated silt subjected to cyclic loading with complex stress path in marine environment are available. Using the GDS hollow cylinder apparatus, a series of undrained tests is performed on the remolded saturated silt under combined axial-torsional cyclic loading for simulating changes in the amplitude of the wave and the depth of seabed. To take the generalized shear strain γ_g = 5% as the liquefaction triggering criteria, the influences of cyclic stress paths(cyclic stress ratio CSR and cyclic loading amplitude ratio δ) on the undrained behavior of saturated silt under isotropic consolidation conditions are studied. The test results show that the effects of CSR and δ on the development patterns of excess pore pressure and deformation of saturated silt are significant. The saturated silt under the cyclic loading with circular stress path(δ= 1) is the most susceptible to liquefaction. The liquefaction of saturated silt is not triggered when CSR≤ 0.050, but when CSR≥ 0.065 and δ= 1, the liquefaction of saturated silt can be triggered, and the saturated silt is more susceptible to liquefaction when CSR > 0.150. The correlation between γ_g and excess pore pressure ratio(r_u) is less influenced by CSR and δ, and the γ_g can be characterized by the tangent function of r_u. When the equivalent cyclic stress ratio ESR is uesd as the index of the amplitude of cyclic stress with complex stress paths, the liquefaction number of cycles(N_L) required to cause γ_g = 5% may be uniquely correlated to the applied ESR, and the ESR decreases with the increase of N_L.
引文
[1]JENG D S.Mechanism of the wave-induced seabed instability in the vicinity of a breakwater:a review[J].Ocean Engineering,2001,28(5):537-570.
[2]MEJIA L H,YEUNG M R.Liquefaction of coralline soils during the 1993 Guam earthquake[C]//Proceedings of Sessions Held in Conjunction with the ASCEConvention.San Diego:[s.n.],1995.
[3]CHOCK G,ROBERTSON I,NICHOLSON P,et al.Compilation of observations of the October 15,2006Kiholo Bay(Mw 6.7)and Mahukona(Mw 6.0)earthquakes,Hawai'i[R].Hawaii:the Earthquake Engineering Research Institute and the Structural Engineers Association of Hawaii,2006.
[4]OLSON S M,GREEN R A,LASLEY S,et al.Documenting liquefaction and lateral spreading triggered by the 12 January 2010 Haiti earthquake[J].Earthquake Spectra,2012,27(Suppl.1):S93-S116.
[5]周正龙,陈国兴,吴琪.初始剪应力对饱和粉土液化特性影响试验研究[J].岩土工程学报,2016,38(3):504-509.ZHOU Zheng-long,CHEN Guo-xing,WU Qi.Effect of initial static shear stress on liquefaction behavior of saturated silt[J].Chinese Journal of Geotechnical Engineering,2016,38(3):504-509.
[6]周正龙,陈国兴,吴琪.初始剪应力对饱和粉土液化大变形特性的影响[J].岩土力学,2017,38(5):1314-1320.ZHOU Zheng-long,CHEN Guo-xing,WU Qi.Effect of initial static shear stress on liquefaction and large deformation behaviors of saturated silt[J].Rock and Soil Mechanics,2017,38(5):1314-1320.
[7]HYDE A F,HIGUCHI T,YASUHARA K.Liquefaction,cyclic mobility,and failure of silt[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(6):716-735.
[8]ISHIHARA K,TOWHATA I.Sand response to cyclic rotation of principal stress directions as induced by wave loads[J].Soils and Foundations,1983,23(4):11-26.
[9]ISHIHARA K,YAMAZAKI A.Analysis of wave-induced liquefaction in seabed deposits of sand[J].Soils and Foundations,1984,24(3):85-100.
[10]WANG Z T,LIU P,JENG D,et al.Cyclic strength of sand under a nonstandard elliptical rotation stress path induced by wave loading[J].Journal of Hydrodynamics,2017,29(1):89-95.
[11]李男,黄博,凌道盛,等.斜椭圆应力路径下饱和松砂动力特性试验研究[J].岩土力学,2015,36(1):156-162.LI Nan,HUANG Bo,LING Dao-sheng,et al.Experimental research on behaviors of saturated loose sand subjected to oblique ellipse stress path[J].Rock and Soil Mechanics,2015,36(1):156-162.
[12]郭莹.复杂应力条件下饱和松砂的不排水动力特性试验研究[D].大连:大连理工大学,2003.GUO Ying.Experimental studies on undrained cyclic behavior of loose sands under complex stress conditions considering static and cyclic coupling effect[D].Dalian:Dalian University of Technology,2003.
[13]潘华,陈国兴,刘汉龙.变幅波浪荷载下饱和南京细砂残余孔隙水压力特性[J].岩石力学与工程学报,2011,30(4):843-849.PAN Hua,CHEN Guo-xing,LIU Han-long.Residual Pore water pressure properties of Nanjing’s saturated fine sand under wave loads with variable amplitudes[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(4):843-849.
[14]张健,高玉峰,沈扬,等.波浪荷载作用下饱和粉土反正弦孔压拟合参数影响因素分析[J].岩土力学,2011,32(3):727-732.ZHANG Jian,GAO Yu-feng,SHEN Yang,et al.Factor analysis of fitting parameter for saturated silt arcsin pore water pressure under wave loading[J].Rock and Soil Mechanics,2011,32(3):727-732.
[15]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.
[16]WANG Y K,GAO Y F,GUO L,et al.Cyclic response of natural soft marine clay under principal stress rotation as induced by wave loads[J].Ocean Engineering,2017,129:191-202.
[17]周正龙,陈国兴,吴琪.四向振动空心圆柱扭剪仪模拟主应力轴旋转应力路径能力分析[J].岩土力学,2016,37(增刊1):126-132.ZHOU Zheng-long,CHEN Guo-xing,WU Qi.Analysis on capabilities of stress paths of HCA to simulate the principal stress rotation under four dynamic loads[J].Rock and Soil Mechanics,2016,37(Suppl.1):126-132.
[18]王立忠,潘冬子,凌道盛.海床波浪响应的积分变换解及其分析应用[J].岩土工程学报,2006,28(7):847-852.WANG Li-zhong,PAN Dong-zi,LING Dao-sheng.Analysis of integral transform of the wave-induced response in seabed and its application[J].Chinese Journal of Geotechnical Engineering,2006,28(7):847-852.
[19]ANDERSON K H.Bearing capacity under cyclic loading-offshore,along the coast,and on land[J].Canadian Geotechnical Journal,2009,46(5):513-535.
[20]SEED H B,IDRISS I M,ARANGO I.Evaluation of liquefaction potential using field performance data[J].Journal of Geotechnical Engineering,1983,109(3):458-482.
[21]陈国兴,刘雪珠.南京粉质黏土与粉砂互层土及粉细砂的振动孔压发展规律研究[J].岩土工程学报,2004,26(1):79-82.CHEN Guo-xing,LIU Xue-zhu.Study on dynamic pore water pressure in silty clay interbedded with fine sand of Nanjing[J].Chinese Journal of Geotechnical Engineering,2004,26(1):79-82.
[22]HUANG B,CHEN X Y,ZHAO Y.A new index for evaluating liquefaction resistance of soil under combined cyclic shear stresses[J].Engineering Geology,2015,199:125-139.
[23]GEORGIANNOU V N,TSOMOKOS A,STAVROU K.Monotonic and cyclic behaviour of sand under torsional loading[J].Geotechnique,2008,58(2):113-124.
[24]SIVATHAYALAN S,LOGESWARAN P,MANMATHARAJAN V.Cyclic resistance of a loose sand subjected to rotation of principal stresses[J].Journal of Geotechnical and Geoenvironmental Engineering,2015,141(3):04014113-1-04014113-13.
[2]MEJIA L H,YEUNG M R.Liquefaction of coralline soils during the 1993 Guam earthquake[C]//Proceedings of Sessions Held in Conjunction with the ASCEConvention.San Diego:[s.n.],1995.
[3]CHOCK G,ROBERTSON I,NICHOLSON P,et al.Compilation of observations of the October 15,2006Kiholo Bay(Mw 6.7)and Mahukona(Mw 6.0)earthquakes,Hawai'i[R].Hawaii:the Earthquake Engineering Research Institute and the Structural Engineers Association of Hawaii,2006.
[4]OLSON S M,GREEN R A,LASLEY S,et al.Documenting liquefaction and lateral spreading triggered by the 12 January 2010 Haiti earthquake[J].Earthquake Spectra,2012,27(Suppl.1):S93-S116.
[5]周正龙,陈国兴,吴琪.初始剪应力对饱和粉土液化特性影响试验研究[J].岩土工程学报,2016,38(3):504-509.ZHOU Zheng-long,CHEN Guo-xing,WU Qi.Effect of initial static shear stress on liquefaction behavior of saturated silt[J].Chinese Journal of Geotechnical Engineering,2016,38(3):504-509.
[6]周正龙,陈国兴,吴琪.初始剪应力对饱和粉土液化大变形特性的影响[J].岩土力学,2017,38(5):1314-1320.ZHOU Zheng-long,CHEN Guo-xing,WU Qi.Effect of initial static shear stress on liquefaction and large deformation behaviors of saturated silt[J].Rock and Soil Mechanics,2017,38(5):1314-1320.
[7]HYDE A F,HIGUCHI T,YASUHARA K.Liquefaction,cyclic mobility,and failure of silt[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(6):716-735.
[8]ISHIHARA K,TOWHATA I.Sand response to cyclic rotation of principal stress directions as induced by wave loads[J].Soils and Foundations,1983,23(4):11-26.
[9]ISHIHARA K,YAMAZAKI A.Analysis of wave-induced liquefaction in seabed deposits of sand[J].Soils and Foundations,1984,24(3):85-100.
[10]WANG Z T,LIU P,JENG D,et al.Cyclic strength of sand under a nonstandard elliptical rotation stress path induced by wave loading[J].Journal of Hydrodynamics,2017,29(1):89-95.
[11]李男,黄博,凌道盛,等.斜椭圆应力路径下饱和松砂动力特性试验研究[J].岩土力学,2015,36(1):156-162.LI Nan,HUANG Bo,LING Dao-sheng,et al.Experimental research on behaviors of saturated loose sand subjected to oblique ellipse stress path[J].Rock and Soil Mechanics,2015,36(1):156-162.
[12]郭莹.复杂应力条件下饱和松砂的不排水动力特性试验研究[D].大连:大连理工大学,2003.GUO Ying.Experimental studies on undrained cyclic behavior of loose sands under complex stress conditions considering static and cyclic coupling effect[D].Dalian:Dalian University of Technology,2003.
[13]潘华,陈国兴,刘汉龙.变幅波浪荷载下饱和南京细砂残余孔隙水压力特性[J].岩石力学与工程学报,2011,30(4):843-849.PAN Hua,CHEN Guo-xing,LIU Han-long.Residual Pore water pressure properties of Nanjing’s saturated fine sand under wave loads with variable amplitudes[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(4):843-849.
[14]张健,高玉峰,沈扬,等.波浪荷载作用下饱和粉土反正弦孔压拟合参数影响因素分析[J].岩土力学,2011,32(3):727-732.ZHANG Jian,GAO Yu-feng,SHEN Yang,et al.Factor analysis of fitting parameter for saturated silt arcsin pore water pressure under wave loading[J].Rock and Soil Mechanics,2011,32(3):727-732.
[15]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.
[16]WANG Y K,GAO Y F,GUO L,et al.Cyclic response of natural soft marine clay under principal stress rotation as induced by wave loads[J].Ocean Engineering,2017,129:191-202.
[17]周正龙,陈国兴,吴琪.四向振动空心圆柱扭剪仪模拟主应力轴旋转应力路径能力分析[J].岩土力学,2016,37(增刊1):126-132.ZHOU Zheng-long,CHEN Guo-xing,WU Qi.Analysis on capabilities of stress paths of HCA to simulate the principal stress rotation under four dynamic loads[J].Rock and Soil Mechanics,2016,37(Suppl.1):126-132.
[18]王立忠,潘冬子,凌道盛.海床波浪响应的积分变换解及其分析应用[J].岩土工程学报,2006,28(7):847-852.WANG Li-zhong,PAN Dong-zi,LING Dao-sheng.Analysis of integral transform of the wave-induced response in seabed and its application[J].Chinese Journal of Geotechnical Engineering,2006,28(7):847-852.
[19]ANDERSON K H.Bearing capacity under cyclic loading-offshore,along the coast,and on land[J].Canadian Geotechnical Journal,2009,46(5):513-535.
[20]SEED H B,IDRISS I M,ARANGO I.Evaluation of liquefaction potential using field performance data[J].Journal of Geotechnical Engineering,1983,109(3):458-482.
[21]陈国兴,刘雪珠.南京粉质黏土与粉砂互层土及粉细砂的振动孔压发展规律研究[J].岩土工程学报,2004,26(1):79-82.CHEN Guo-xing,LIU Xue-zhu.Study on dynamic pore water pressure in silty clay interbedded with fine sand of Nanjing[J].Chinese Journal of Geotechnical Engineering,2004,26(1):79-82.
[22]HUANG B,CHEN X Y,ZHAO Y.A new index for evaluating liquefaction resistance of soil under combined cyclic shear stresses[J].Engineering Geology,2015,199:125-139.
[23]GEORGIANNOU V N,TSOMOKOS A,STAVROU K.Monotonic and cyclic behaviour of sand under torsional loading[J].Geotechnique,2008,58(2):113-124.
[24]SIVATHAYALAN S,LOGESWARAN P,MANMATHARAJAN V.Cyclic resistance of a loose sand subjected to rotation of principal stresses[J].Journal of Geotechnical and Geoenvironmental Engineering,2015,141(3):04014113-1-04014113-13.