强度弱化条件下饱和砂土地基中桩-土相互作用p-y曲线研究  

Research on p-y curves of soil-pile interaction in saturated sand foundation in weakened state

作　　者：张小玲[1,2] 朱冬至 许成顺[1,2] 杜修力[1,2] ZHANG Xiao-ling;ZHU Dong-zhi;XU Cheng-shun;DU Xiu-li(College of Architecture and Civil Engineering,Beijing University of Technology,Beijing 100124,China;Key Laboratory of Urban Security and Disaster Engineering,Ministry of Education,Beijing University of Technology,Beijing 100124,China)

机构地区：[1]北京工业大学建筑工程学院,北京100124 [2]北京工业大学城市与工程安全减灾教育部重点实验室,北京100124

出　　处：《岩土力学》2020年第7期2252-2260,共9页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.51778020);国家自然科学基金创新研究群体项目(No.51421005)。

摘　　要：在地震荷载作用下,可液化土层中的桩基础往往会由于地基土体液化而发生破坏。在此过程中即使土体最终没有达到完全液化,但由于超孔隙水压力的存在,饱和砂土会发生强度弱化,也会导致土体对桩身水平抗力的降低。此时若不考虑超孔隙水压力对土抗力的影响,仍然采用API规范中的p-y曲线对桩基础进行设计,结果将偏于危险。针对这种情况,首先利用竖向-扭转双向耦合剪切仪对饱和砂土进行了循环扭剪动强度试验,研究了不同弱化状态下饱和砂土的动力特性和弱化参数;然后基于浅层处改进的土楔体理论模型推导极限土抗力公式,并结合深层处的绕桩流动破坏理论模型,得到了任意深度处不同孔压比下的极限土抗力,进而构造了不同弱化状态下饱和砂土地基中桩-土相互作用的p-y曲线。通过研究发现:表征土体强度弱化状态的孔压比对桩-土相互作用的极限土抗力的影响非常显著,孔压比越大,土体强度弱化程度越严重,饱和砂土的极限土抗力值就越小,即横向受荷桩对周围土体的作用随着土体强度弱化程度的增加而降低,反之则增大。Under seismic loading,the pile foundations in the liquefiable soil are often destroyed due to the liquefaction of foundation soil.In this process,even if the soil does not reach full liquefaction finally,the strength of saturated sand will be weakened due to the existence of the excess pore water pressure,which will also lead to the decrease of horizontal resistance force of soil.If the influence of excess pore water pressure on horizontal resistance force of soil is not considered,the pile foundations are still designed by adopting the p-y curves in the API standard,and the results will be more dangerous.In this paper,the dynamic cyclic torsional shear tests are carried out for the Fujian standard sands by employing the vertical-torsional coupling shear apparatus,and the dynamic characteristics and weakened parameters of saturated sands in different weakened states are studied.Then the formulas of ultimate soil resistance are derived based on the improved theoretical model of soil wedge at shallow layer.Combined with the theoretical model of flow failure around piles at deep layer,the ultimate soil resistances at different pore pressure ratios at any depth are obtained,and then the p-y curves of pile-soil interaction in saturated sand foundation in different weakened states are constructed.It can be found from the study that the pore pressure ratio,which characterizes the weakened state of soil,has a significant effect on the ultimate soil resistance in pile-soil interaction.With the increase of pore pressure ratio,the weakened degree of soil will be more serious,and the ultimate resistance of saturated sand is smaller.That is to say,the action of the lateral loaded pile on the surrounding soil decreases with the increase of soil weakened degree,and the vice versa.

关 键 词：桩-土相互作用 超孔隙水压力 弱化参数 P-Y曲线 

分 类 号：TU279.76[建筑科学—建筑设计及理论]