可液化回填土中重力码头地震旋转残余角位移的拟动力法计算
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摘要
地震残余旋转位移的预测是重力码头地震工程设计中的关键,而码头身后地下水位下的回填砂土因地震作用引起的超静孔隙水压力的时程发展水平对码头运动的残余位移起着重要的影响。引用液化度概念定义超静孔隙水压力比发展水平,考虑液化度的时程特征和墙土体系的惯性影响,采用考虑时间、相位差和地震波放大效应的拟动力法计算码头-回填土体系的惯性力与作用在码头上的动主动土压力。根据力矩极限平衡确定旋转门槛加速度系数,运用旋转块体法初步推导码头作单独旋转运动的地震残余角位移计算公式。应用该计算方法对一算例进行详细分析,比较考虑液化度与未考虑液化度两种工况下的角位移时程变化规律和各自的残余角位移,结果表明:可液化回填砂土中的重力码头在地震安全设计中需重视回填砂土的液化度对码头变形的影响。
Predicting the residual rotational displacement induced by earthquake load is a key research aspect for the seismic design of quay wall.The motion of quay wall is influenced greatly by the development of excess pore water pressure in backfill.In the present study,the index of extent of liquefaction is employed to consider the effect of excess pore water pressure in backfill,and the time characteristics of the extent of liquefaction and the inertia effect of the quay wall-backfill soil are considered.In the proposed pseudo-dynamic method,time,phase difference and effects of amplification in earthquake waves on calculating inertia forces and dynamic active earth pressure of the system of quay wall and backfill soil are considered.Rotation threshold acceleration coefficient is confirmed by equilibrium of moments,and the calculation method for seismic rotational displacement of gravity quay is developed primarily by rotating block method.An example is shown presented,and temporal variations of angular displacement and residual angular displacement are analyzed and compared for situations with and without considering extent of liquefaction,respectively.It is found that the extent of liquefaction of backfill soil is important for the seismic safety design of gravity quay walls.
Predicting the residual rotational displacement induced by earthquake load is a key research aspect for the seismic design of quay wall.The motion of quay wall is influenced greatly by the development of excess pore water pressure in backfill.In the present study,the index of extent of liquefaction is employed to consider the effect of excess pore water pressure in backfill,and the time characteristics of the extent of liquefaction and the inertia effect of the quay wall-backfill soil are considered.In the proposed pseudo-dynamic method,time,phase difference and effects of amplification in earthquake waves on calculating inertia forces and dynamic active earth pressure of the system of quay wall and backfill soil are considered.Rotation threshold acceleration coefficient is confirmed by equilibrium of moments,and the calculation method for seismic rotational displacement of gravity quay is developed primarily by rotating block method.An example is shown presented,and temporal variations of angular displacement and residual angular displacement are analyzed and compared for situations with and without considering extent of liquefaction,respectively.It is found that the extent of liquefaction of backfill soil is important for the seismic safety design of gravity quay walls.
引文
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[7]Choudhury D,Nimbalkar S.Seismic rotational displacementof gravity walls by pseudo-dynamic method:Passive case[J].Soil Dynamics and Earthquake Engineering,2007,27(3):242-249
[8]王丽艳,刘汉龙.含地下水的回填砂土中重力式岸墙地震残余角位移的拟静力计算[J].水利学报,2009,40(5):623-629(Wang Liyan,Liu Hanlong.Seismicresidual angular displacement of gravity wall by pseudo-static method in backfill sand with groundwater[J].Journal of Hydraulic Engineering,2009,40(5):623-629(in Chinese))
[9]王丽艳,刘汉龙,蔡艳.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 Liyan,Liu Hanlong,Cai Yan.Discussionon assessment of earth-structure liquefaction deformationbased on the concept of degree of liquefaction[J].Journalof Disaster Prevention and Mitigation Engineering,2007,27(4):451-456(in Chinese))
[10]刘汉龙,王丽艳.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[J].岩土工程学报,2009,31(5):686-691(Liu Hanlong,Wang Liyan.Seismicresidual displacement of gravity quay walls under coupledmotion between rotation and sliding by simple methook[J].Chinese Journal of Geotechnical Engineering,2009,31(5):686-691(in Chinese))
[2]Pianc A.Seismic design guidelines for port structures[M].Belgium:International Navigation Association,2001
[3]ISO23469 Bases for design of structures-seismic actions fordesigning geotechnical works[S]
[4]Steedman R S,Zeng X.The influence of phase on thecalculation of pseudo-static earth pressure on a retainingwall[J].Geotechnique,1990,40(1):103-112
[5]Zeng X,Steedman R S.Rotating block method for seismicdisplacement of gravity walls[J].Journal of Geotechnicaland Geoenvironmental Engineering,2000,126(8):709-717
[6]Choudhury D,Nimbalkar S.Seismic passive resistance bypseudo-dynamic method[J].Geotechnique,2005,55(9):699-702
[7]Choudhury D,Nimbalkar S.Seismic rotational displacementof gravity walls by pseudo-dynamic method:Passive case[J].Soil Dynamics and Earthquake Engineering,2007,27(3):242-249
[8]王丽艳,刘汉龙.含地下水的回填砂土中重力式岸墙地震残余角位移的拟静力计算[J].水利学报,2009,40(5):623-629(Wang Liyan,Liu Hanlong.Seismicresidual angular displacement of gravity wall by pseudo-static method in backfill sand with groundwater[J].Journal of Hydraulic Engineering,2009,40(5):623-629(in Chinese))
[9]王丽艳,刘汉龙,蔡艳.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 Liyan,Liu Hanlong,Cai Yan.Discussionon assessment of earth-structure liquefaction deformationbased on the concept of degree of liquefaction[J].Journalof Disaster Prevention and Mitigation Engineering,2007,27(4):451-456(in Chinese))
[10]刘汉龙,王丽艳.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[J].岩土工程学报,2009,31(5):686-691(Liu Hanlong,Wang Liyan.Seismicresidual displacement of gravity quay walls under coupledmotion between rotation and sliding by simple methook[J].Chinese Journal of Geotechnical Engineering,2009,31(5):686-691(in Chinese))
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