门架式双排抗滑桩设计计算新模式

A new mode for calculation of portal double row anti-sliding piles

门架式双排抗滑桩是一种新型的支挡结构。这种结构具有较大的刚度,可以有效地限制支挡结构的变形,具有桩顶位移小,抵抗力大的特点。但其受力机理复杂,前、后排桩间土对结构的作用很难确定。针对这一问题,提出了一个新的计算模式:将前、后排桩及中间连系梁和桩间土视为一个整体;前排桩和后排桩受到的地基土的抗力简化为弹性支承,提出了桩间土对前排桩的作用模式和作用力计算分析模型,认为前排桩不仅受到桩间土的主动土压力作用,而且受到由于桩间土的挤压作用而产生的附加土压力的作用; 其主动土压力 qa 与单排桩所受到的主动土压力σa 之比是桩间距与桩宽(桩径)之比的二次抛物线函数;而附加土压力 qb 可由半平面体在边界上受法向分布力的解析解[1]求得;而桩间土对后排桩的作用按照弹性支承考虑。最后,采用有限元理论和 Winkler 弹性地基梁方法建立了求解门架式双排抗滑桩内力的力学模型,并应用于某供水工程的边坡加固中。计算结果表明:该种计算分析模式是合理可行的,具有一定的推广应用价值。

As a new bracing structure, the portal double row piles have some advantages such as larger rigidity, less displacement in the top of the piles and large anti-force, which leads to the restriction of piles deformation. The key problem is concentrated on the determination of the action of soil between the double piles. On the basis of combining the front and the back row piles as well as connecting beams and soils as a whole structure, and simplifying the forces for the double row piles from the soils as elastic bearing, a new analytical mode and a new calculation model are proposed. From the viewpoint of the authors, the front row piles sustain not only the active earth pressure but also the additional one due to the press of the soils between the double piles. The ratio of the active earth pressure qa for the double row piles to the active earth pressure for the single onesσ a is a parabola function of the ratio of interval of the piles to the diameter of the piles. The action of the soils to the back row piles is considered as elastic bearing; its mathematical and mechanical model for the internal force of portal double-row piles is established by finite element method and Winkler beam on elastic foundation method. The application of the models to the water supply reconstruction project from Dongjiang to Shenzhen shows that the new mode and the calculation model is reasonable and can be used in the similar engineering.