桩-液化土相互作用p-y关系分析
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摘要
基于多工况的桩-液化土体动力相互作用振动台试验,研究地震荷载作用下液化土层中桩土间侧向相互作用力p与桩身和土体间侧向相对位移y之间的关系。将试验得到的实际p-y曲线与采用拟静力法和以API规范为基础的折减系数法计算出的p-y曲线进行对比,结果表明:(1)液化土层中试验得到的桩真实p-y响应及由拟静力法和折减系数法得到的结果都呈非线性变化,三者极限状态有接近一致的趋势,但变化过程差异明显;(2)采用拟静力法和折减系数法都会使液化土层桩基础侧向反力迅速增长,很快达到屈服极限,远远超过实际情况,会导致相当保守的结果;(3)液化进程中控制桩p-y响应的是土体位移而非惯性力,因而拟静力法和折减系数法的原理不适合桩-液化土体动力相互作用分析,不能用于液化土层中桩基础地震响应的计算。
In terms of the dynamic interaction between the pile foundation and the liquefied soil layer based on shaking table tests,the relationship of the interaction lateral force p between the pile and the surrounding soil layer with the relative lateral displacements y between the pile and surrounding soil layer is investigated.Comparison of the actual behavior resulting from the testes and those from the pseudo-static method and rigidity-reduction method indicates that the dynamic p-y curves from the tests and from the pseudo-static and rigidity-reduction methods show nearly same limit state but the processes are quite different.The lateral interaction force in the liquefied soil layer by the pseudo-static and the rigidity-reduction methods rapidly increases and reaches the yield state.This is obviously larger than the actual situation and leads to quite conservative results.The dominant factor in the liquefied soil layer is soil displacement rather than the inertia force of the superstructure and the pseudo-static and the rigidity-reduction methods are not suitable for simulating the response of pile foundation on the liquefiable soil layers.
In terms of the dynamic interaction between the pile foundation and the liquefied soil layer based on shaking table tests,the relationship of the interaction lateral force p between the pile and the surrounding soil layer with the relative lateral displacements y between the pile and surrounding soil layer is investigated.Comparison of the actual behavior resulting from the testes and those from the pseudo-static method and rigidity-reduction method indicates that the dynamic p-y curves from the tests and from the pseudo-static and rigidity-reduction methods show nearly same limit state but the processes are quite different.The lateral interaction force in the liquefied soil layer by the pseudo-static and the rigidity-reduction methods rapidly increases and reaches the yield state.This is obviously larger than the actual situation and leads to quite conservative results.The dominant factor in the liquefied soil layer is soil displacement rather than the inertia force of the superstructure and the pseudo-static and the rigidity-reduction methods are not suitable for simulating the response of pile foundation on the liquefiable soil layers.
引文
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[2]丁剑霆,姜淑珍,包峰.唐山地震桥梁震害回顾[J].世界地震工程,2006,22(1):67-71.
[3]日本阪神大地震考察[M].北京:地震出版社,1995.
[4]李雨润,袁晓铭.液化场地上土体侧向变形对桩基影响研究述评[J].世界地震工程,2004,20(2):17-22.
[5]Daniel W,Wilson,et al.Observed seismic lateral resistance of liquefying sand[J].Journal of Geotechnical and Geoenvironmental Engineering.2000,898-906.
[6]American Petroleum Inst.Recommended practice for planning,designing,and constructing fixed offshore platforms[R].Working Stress Design,Rpt.RP 2A-WSD.Washington:American Petroleum Inst,1976.
[7]袁晓铭,李雨润,孙锐.地面横向往返运动下可液化土中桩基响应机理[J].土木工程学报,2008(已接受).
[8]张舒羽.水平承载桩静载P-Y曲线研究[D].南京:河海大学,2001.
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