扩底桩承载力空间屈服包络面的基本特性

通过扩底桩的土槽载荷试验和离心机仿真模型试验，对不同类型荷载之间的相互影响、组合荷载作用下桩的抵抗机理和承载力屈服包络面的特性进行了分析。结果表明：铅直、水平荷载作用下桩的承载力屈服包络线，弯矩、水平荷载作用下的承载力屈服包络线都可近似地用椭圆来表现。屈服包络线可用桩的单方向极限承载力的经验公式来生成。根据承载力空间屈服面的连续性，提出了用桩的单方向极限承载力Vm，Hm，Um和Mm求解桩的承载力空间屈服面的经验公式。在桩的设计计算过程中，必须考虑铅直荷载、水平荷载及弯矩荷载间的相互影响。

Three dimensional failure envelope behavior of pedestal piles

An experimental program to investigate the behavior of pedestal pile under combinatorial loads in dense sand is put forward through 1oading test and centrifuge test.The work focused on evaluating the shape of failure envelope surface of combinatorial loaded pile.The measured data and phenomenon are discussed.As a result,the following behaviors have been clarified: The failure curve on M=H h plane is an ellipse approximately,which can roughly estimated by an equation from Vm,Hm,and Um.The failure curve on M-H plane also was an ellipse approximately;this ellipse can be determined by results of two laterally loaded pile tests.If Um,Vm,Hm and Mm are known or assumed,the failure envelope surface can be obtained by the equation.The interaction among vertical,lateral and bending load must be considered in the design of pile foundation.