饱和砂土动力液化到渗流液化过程探讨
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摘要
根据饱和砂土地层地震液化现象及饱和砂土动力学试验所观察到的现象 ,本文从砂粒～孔隙水两相介质相互作用的角度出发 ,研究饱和砂土在振动荷载作用下的液化过程和机制。研究结果表明 ,饱和砂土受振 ,砂粒相对滑动并重新排列 ,孔隙率降低 ,孔隙水受压产生超静孔水压力并不断增大 ,部分孔隙水挤出渗流 ,隙水渗流对砂粒产生渗流压力。渗流压力与超静孔隙水压力迭加 ,形成的上托力等于或大于砂粒水中重力时 ,砂粒在隙水中处于悬浮状态。此时 ,饱和砂土宏观上表现为液态。为此 ,根据下沉砂粒与向上渗流孔隙水之间相对运动过程中的动力作用特征 ,建立了描述饱和砂土液化过程的模型和液化判据
Based on the liquefaction phenomena observed of saturated sand soil under seismic action and in dynamic test, and from the interaction between water and sand grain, the liquefaction mechanism and procedure of saturated sand under vibrational load were analyzed in this paper. The results from the study show that when saturated sand soil was librated, sand grain will slide and rearrange each other, pore ratio reduce, excess hydrostatic pressure produce and continually increase. At that time, some pore water will be extruded and seepage out. The seepage of the pore water produces seepage pressure on the sinking sand grain. When the sum of the seepage pressure and excess hydrostatic pressure is equal to gravity of sinking sand grain, the sand grain suspends in pore water and the saturated sand soil shows liquid state in macrocosm. The model described the procedure from dynamic liquefaction to seepage liquefaction and liquefaction criterion of saturated sand soil were established.
Based on the liquefaction phenomena observed of saturated sand soil under seismic action and in dynamic test, and from the interaction between water and sand grain, the liquefaction mechanism and procedure of saturated sand under vibrational load were analyzed in this paper. The results from the study show that when saturated sand soil was librated, sand grain will slide and rearrange each other, pore ratio reduce, excess hydrostatic pressure produce and continually increase. At that time, some pore water will be extruded and seepage out. The seepage of the pore water produces seepage pressure on the sinking sand grain. When the sum of the seepage pressure and excess hydrostatic pressure is equal to gravity of sinking sand grain, the sand grain suspends in pore water and the saturated sand soil shows liquid state in macrocosm. The model described the procedure from dynamic liquefaction to seepage liquefaction and liquefaction criterion of saturated sand soil were established.
引文
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[3]B .V .Degregorio,Amodelofdilatation,densification,andstaticliquefactionofloosesand,MathematicalGeology,No.1,Vol.22,P1～13,1990.
[4]S .Pietruszezak,Modelingofsandbehaviorunderearthquakeexcitation,InternationalJournalofNumericalandAnalyticalMethodsinGeo mechanics,No.3,Vol.11,P221～240,1987.
[5]G .Bouckovalas,Computationalmodelforsaturatedsandsubjectedtocyclicloading,SoilsandFoundation,No.4,Vol.27,P34～44,1987.
[6]M .Yoshikawa,Dynamicbehaviorofamodelsaturatedsandduringliquefaction,SoilMechanicsAndFoundationEngineering,No.12,Vol.34,P45～51,1986.
[7]F .Oka,Aconstitutivemodelforsandbasedonthenon linearkinematichardeningruleanditsapplication,proceedings.
[8]Y .Lou,Amethodfortwo dimensionaleffectivestressanalysisofsandliquefaction,JournalofHydraulicEngineering,P56～59,No.2,1985.
[9]K .Zen,Evaluationofdrainageeffectinsandliquefaction,ProceedingsoftheEleventhInternationalConferenceonSoilMechanicsandFoundationEngineering,P1931～1934,1985.
[10]F .Guan,Studyonthemethodsforanalysisofsandliquefactionduringearthquake,EarthquakeEngineeringandEngineeringVibration,P54～66,No.4,Vol.8,1998.
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[12]D .V .Ramsamooj,Modelpredictionofcyclicresponseofsoils,JournalofGeo technicalEngineering,P1053～1072,No.7,Vol.116,1990.
[13]X .M .Chen,Indeterminategraypredictionmethodofpossibilityofsandliquefactionduringearthquake,JournalofGuilinInstituteofTechnology,P106～109,No.2,Vol.17,1997.
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[15]成都科学技术大学河床动力学(第一版)[M]北京:水利电力出版社,1986.
[16]河海大学土工原理与计算(第二版)[M]北京:水利电力出版社,1992.
[17]李诗久工程流体力学(第一版)[M]北京:机械工业出版社,1980
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