振动桩锤沉桩过程液化特性和贯入度数值分析
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摘要
以液压振动桩锤和地基土为研究对象,运用有限元差分软件FLAC3D的流固耦合动力时程分析模块,采用Finn液化本构关系建立了桩土相互作用液化数值分析模型,利用内置FISH函数,对已有的变量进行计算,引入超孔压比描述地基土液化情况,模拟地基土振动液化沉桩过程。分析了振动频率、静载荷和弹性模量对桩贯入度和液化特性的影响。研究结果表明:振动沉桩引起的超孔压比的增加可以提高桩的贯入度;激振频率在20 Hz以内,振动频率越高,超孔压比上升的速率越快,桩贯入度增加;地基土弹性模量增大,桩下沉阻力增大,使桩下沉困难,可通过提高激振频率,增加桩顶静载荷来实现桩的下沉。
Vibratory pile and ground soil were chosen as objectives to study pile-soil interaction in liquefaction using finite element difference software FLAC3D.The numerical simulation model for ground soil liquefaction was established by using Finn constitutive relation;furthermore,the ground soil liquefaction during vibratory hammer driving was simulated by using fluid-solid interaction and dynamic time-history analysis module.By using FISH inner function of the code,the known variables were calculated.The process of soil liquefaction was described by excess pore pressure ratio and the effects of stimulating frequency,static loading and elastic modulus of the soil foundation on the liquefaction and driving penetration were analyzed.The results show that pile penetration speed increases with the increase of excess pore pressure ratio which is caused by vibration sinking pile.Within 20 Hz,the higher the vibration frequency applied,the faster the rising rate of excess pore pressure and the deeper of the penetration were observed.Enlarging the elastic modulus of the ground soil results in the increase of penetration resistance for sinking the pile.By increasing vibration frequency,the amount of static load is increased for submersing the piles.
Vibratory pile and ground soil were chosen as objectives to study pile-soil interaction in liquefaction using finite element difference software FLAC3D.The numerical simulation model for ground soil liquefaction was established by using Finn constitutive relation;furthermore,the ground soil liquefaction during vibratory hammer driving was simulated by using fluid-solid interaction and dynamic time-history analysis module.By using FISH inner function of the code,the known variables were calculated.The process of soil liquefaction was described by excess pore pressure ratio and the effects of stimulating frequency,static loading and elastic modulus of the soil foundation on the liquefaction and driving penetration were analyzed.The results show that pile penetration speed increases with the increase of excess pore pressure ratio which is caused by vibration sinking pile.Within 20 Hz,the higher the vibration frequency applied,the faster the rising rate of excess pore pressure and the deeper of the penetration were observed.Enlarging the elastic modulus of the ground soil results in the increase of penetration resistance for sinking the pile.By increasing vibration frequency,the amount of static load is increased for submersing the piles.
引文
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[3]王凯,杨铭,马辉,等.基于ANSYS软件的振动沉桩过程仿真[J].机械与电子,2007(8):65-67.
[4]滕云楠,任朝辉,王月,等.振动沉桩系统动力学特性及运动仿真分析[J].仪器仪表学报,2010,31(4):44-47.
[5]魏楠,宋春雨,陈龙珠.饱和地基高频振动下孔压特性的数值分析[J].铁道建筑,2008(8):88-91.
[6]罗春雷,刘丹.国外振动沉桩建模分析方法[J].建筑机械,2005(6):62-66.
[7]MASOUMI H R,DEGRANDE G,LOMBAERT G.Prediction of free field vibrations due to pile driving using a dynamicsoil-structure interaction formulation[J].Soil Dynamics and Earthquake Engineering,2007,27(2):1-18.
[8]陈育民,刘汉龙,赵楠.抗液化刚性排水桩振动台试验的数值模拟研究[J].土木工程学报,2010,43(27):114-119.
[9]MARDIN G B,FINN W D L,SEED H B.Fundamentals of liquefaction under cyclic loading[J].Journal of GeotechnicalEngineering Division,1975,101(5):423-438.
[10]何剑平,陈卫忠.自由场典型液化特征数值模拟试验[J].地震工程与工程振动,2011,31(2):162-169.
[11]吴世明,徐攸在.土动力学现状与发展[J].岩土工程学报,1998,20(3):125-131.
[12]张金来,鲁晓兵,王淑云,等.水平动载下饱和砂土地基液化区扩展[J].岩土工程技术,2004,18(1):8-10.
[13]宋兵,蔡健.桩土临界位移的研究[J].广西大学学报:自然科学版,2010,35(4):655-660.
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