铅直、水平荷载作用下扩底桩的承载机理

Resistance Behaviors of pile with Enlarged Base under Axial and Lateral Loads

根据扩底桩组合荷载的载荷试验结果,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线的特性作了初步分析探讨,得出以下结果:铅直荷载和水平荷载、水平荷载和弯矩荷载之间在承载力方面存在着一定的相互影响;铅直、水平荷载作用下桩的承载力屈服包络线可近似地用一个偏离坐标原点的椭圆来表现,此包络线可用包括桩的单方向极限承载力Vm,Hm和Um的关系式得到;弯矩、水平荷载作用下的承载力屈服包络线也可以近似地用椭圆来表现,此包络线可根据两次不同加载高度的水平载荷试桩结果的关系式求得;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。

This paper presents the experimental results obtained from investigating the behaviors of pile with enlarged base under axial and lateral loads in dense sand in laboratory. The work focused on evaluating the mutual influences among different loads, resistance behaviors of pile under combined loads and the properties of yield envelopes of bearing capacities. The measured data and pleenomena are discussed. As a result, the following behaviors have been carified: There exist certain mutual affections between lateral and vertical loads or lateral and bend loads. The yield envelope curve on M=H.h plane is an ellipse approximately, which can roughly be estimated by an equation from limit bearing loads of V_m,H_(mh) and U_m. The bearing yield load envelope curve on M、H plane is also an ellipse apporoximately, this ellipse can be determined by the result of two laterally loaded pile tests. The interactions among vertical, lateral and bending loads must be considered in the desigh of pile foundation。