重力码头地震旋转与滑动耦合运动下的残余位移简易算法
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摘要
预测重力码头的地震残余位移是码头工程地震设计的关键,而码头墙后回填砂土因地震引起的超静孔隙水压力发展水平对码头墙体运动具有一定的影响。引用液化度概念考虑超静孔隙水压力影响来修正Mononobe-Okabe拟静力法计算的动主动土压力和回填土地震孔隙水产生的动水压力;同时考虑水平和竖向地震载荷,采用Steedman的旋转块体法,根据力与力矩极限平衡确定码头的滑动与旋转门槛加速度系数,分别对码头滑动先开始与倾斜先开始两工况下的耦合运动模式进行详细分析,修正码头因耦合运动影响的滑动与旋转门槛加速度系数,计算码头耦合运动下的地震残余位移计算。选用正弦脉冲的地震运动特征,应用该计算方法对码头耦合运动的残余位移的闭合解进行了推算,分析了码头残余位移随着液化度变化的规律。
Predicting the residual displacements induced by earthquake loading is a key to the seismic design of quay walls,and the motion of quay walls is influenced to some extent by the excess pore water pressure in the backfill acting on the back of quay walls.Considering the effect of excess pore water pressure in the backfill acting on the back of quay walls,the Mononobe-Okabe equivalent static method of calculating the dynamic active earth pressure and the dynamic water pressure in backfill soil is modified by the index of extent of liquefaction.Considering both the horizontal and vertical earthquake waves,the rotation block method of Steedman is applied.The sliding and rotation threshold acceleration coefficients are confirmed by the equilibrium of forces and moments respectively.Two situations of coupled motion with sliding starting first and rotation starting first are analyzed,the sliding and rotation threshold acceleration coefficient are modified because of the effect of coupled motion,and the calculation method of residual displacement of gravity quay walls is developed primarily.An example is shown by the present method under a sine wave of ground motion,and some laws are discussed simply between the extent of liquefaction and the seismic residual displacement.
Predicting the residual displacements induced by earthquake loading is a key to the seismic design of quay walls,and the motion of quay walls is influenced to some extent by the excess pore water pressure in the backfill acting on the back of quay walls.Considering the effect of excess pore water pressure in the backfill acting on the back of quay walls,the Mononobe-Okabe equivalent static method of calculating the dynamic active earth pressure and the dynamic water pressure in backfill soil is modified by the index of extent of liquefaction.Considering both the horizontal and vertical earthquake waves,the rotation block method of Steedman is applied.The sliding and rotation threshold acceleration coefficients are confirmed by the equilibrium of forces and moments respectively.Two situations of coupled motion with sliding starting first and rotation starting first are analyzed,the sliding and rotation threshold acceleration coefficient are modified because of the effect of coupled motion,and the calculation method of residual displacement of gravity quay walls is developed primarily.An example is shown by the present method under a sine wave of ground motion,and some laws are discussed simply between the extent of liquefaction and the seismic residual displacement.
引文
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[5]CHOUDHURY D,NIMBALKAR S S.Seismic rotational displacement of gravity walls by pseudo dynamic method:passive case[J].Geotechnique,2005,55(9):699–702.
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[10]KRAMER S L.Geotechnical earthquake engineering[M].New Jersey:Pearson Education Inc,1996.
[2]STEEDMAN R S,ZENG X.The influence of phase on the calculation of pseudo-static earth pressure on a retaining wall[J].Geotechnique,1990,40(1):103–12.
[3]ZENG X,STEEDMAN R S.Rotating block method for seismic displacement of gravity walls[J].J Geotechn Geoenviron Eng,ASCE,2000,126(8):709–17.
[4]CHOUDHURY D,NIMBALKAR S S.Seismic passive resistance by pseudo dynamic method[J].Geotechnique,2005,55(9):699–702.
[5]CHOUDHURY D,NIMBALKAR S S.Seismic rotational displacement of gravity walls by pseudo dynamic method:passive case[J].Geotechnique,2005,55(9):699–702.
[6]王丽艳,刘汉龙.用液化度概念评价岩土结构地震液化变形的探讨[J].防灾减灾工程学报,2007,27(4):451–456.(Wang Li-yan,Liu han-long.Discussion in Assessment of Geo-structure liquefaction deformation based on degree of liquefaction[J].Journal of Disaster Prevention and Mitigation Engineering,2007,27(4):451–456.(in Chinese))
[7]PIANC.Seismic design guidelines for port structures[S].Japan:Balkema,2001.
[8]ISO,23469.Bases for design of structures-seismic actions for designing geotechnical works[S].Japan:Working Group No.34 of the Maritime Navigation Commission International Navigation Association,2005.
[9]EBELING R M,MORRISON E E Jr.The seismic design of waterfront retaining structures[R].Washington D C:1992.
[10]KRAMER S L.Geotechnical earthquake engineering[M].New Jersey:Pearson Education Inc,1996.
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