非均匀地基中倾斜桩基竖向承载特性模拟试验研究

A simulation test study of vertical bearing capacity of inclined pile foundation in inhomogeneous strata

群桩基础中设计的倾斜桩基以其横向阻抗能力强等优势在港口、码头以及桥梁基础中得到了较为广泛应用。随着山区及不均匀地基土地区高速公路等基础设施的建设,在滑坡、斜坡变形体和不均匀地基上设计倾斜群桩桥梁基础的情况将会越来越多。由于倾斜桩基受力状态的复杂性,目前倾斜桩基础设计仍参考竖向桩基承载力计算理论,凭借经验进行设计。对此人们虽然做了许多探索,但仍未形成完善的设计计算理论和标准。为此,结合厦深客运专线某特大桥桩基选型研究项目,利用相似材料物理模拟试验,就倾角为0°～12°周边斜桩的群桩基础竖向承载力进行了试验研究。结果表明,竖直桩基的荷载-沉降曲线呈缓变型,倾斜桩基则呈陡降型;就倾斜群桩基础竖向承载力而言,倾斜基桩的合理倾角为8°左右;竖直桩基中角桩轴力最大,边桩轴力次之,中桩轴力最小,倾斜桩基中的中桩轴力最大,角桩轴力次之,边桩轴力最小;倾斜桩基桩身弯矩分布形式与基桩的倾角有关,当倾角达到12°时,桩身将出现反向弯曲段。基桩倾角的不同是导致倾斜桩基和竖直桩基竖向承载特性显著不同的主要原因之一。

Inclined pile foundation has been more widely used in the ports,docks and bridge engineering for its superior resistive capability of lateral load.With the construction of highways and other infrastructure in mountains and uneven ground areas,the bridge pile foundation will be more and more adopted in the landslide and similar area.Due to the complex stress state of the inclined pile foundation,its current design theory still refers to the theory of vertical pile foundation and is designed according to the practical experience.Although a lot of exploratory researches have been done,practical calculations theory and design criteria have not yet been formed.Based on that,this paper has conducted physical model test combined with some bridge foundation selection research project in Xiamen-Shenzhen Passenger Dedicated Railway Line.The vertical bearing capacity of pile foundation with inclination of 0°-12 ° has been researched.The results show that load-settlement curve of the vertical pile foundation is slow variant,while that of the inclined pile foundation is steep variant.There is a reasonable pile angle of 8° more or less to exert the vertical bearing capacity of inclined pile foundation.In vertical pile foundation,the largest axial force lies in the corner pile,next in the side pile,then in the middle pile.While in the inclined pile foundation,the largest axial force lies in the middle pile,next in the corner pile,then in the side pile respectively.The pile moment distribution of inclined pile foundation is associated with its pile angle,and the pile moment presents a reverse bending section when the angle reaches 12°.The pile angle difference is the main reason of significantly in different axial bearing properties between inclined pile foundation and vertical pile foundation.