微型桩-锚组合新结构抗滑特性的数值分析

Numerical Analysis of the Anti-sliding Characteristics of the New Micropile-Anchor Composite Structure

针对微型桩加固滑坡时容易出现侧向变形的缺陷,笔者基于综合排桩刚架结构与拉锚式挡土结构形式优点的研发思路,提出了一种微型桩-锚组合抗滑新结构。利用FLAC3D分析了新结构的变形与受力特性,并与传统刚架式微型桩结构进行了比较。结果表明:相比普通刚架式结构,新结构加固后的边坡位移场和桩顶水平位移明显减小,其加固效果和抗滑能力更优;斜向预应力锚索增强了微型桩的侧向刚度,结构变形曲线相对平缓;桩体弯矩、剪力分布相对均匀,发挥了结构的整体受荷能力,且峰值有所降低;除抗弯和抗剪作用外,微型桩还起到轴向作用,尤其是顺坡桩侧摩阻力作用明显;锚索拉力随边坡变形累积而逐渐增大,可以利用稳定地层的自承能力分担部分滑坡荷载;由于锚索预应力的主动施加,结构对桩后土体起到预加固作用,系梁附近桩侧土压力明显增大。研究结果可为该新结构的设计提供一定理论依据。

In order to improve the defect of micropile whose lateral deformation is prone to be excessive when reinforcing slope,based on the idea of the comprehensive utilization of rigid-framed piles and anchored retaining structure,this paper put forward a new composite anti-sliding structure combined with micropiles and anchor. The characteristics of deformation and stress of the newly proposed structure were analyzed by the FLAC3 Dsoftware,and it was compared with the traditional layout. The results indicated that the displacement field of slope reinforced by the new structure reduced obviously,so did the horizontal displacement of pile top. The reinforcing effect and anti-sliding capacity of the new structure were better than the traditional framed structure. The inclined prestressed anchor enhanced the lateral stiffness of the retaining system effectively,making the lateral deformation along the pile distribute relatively uniform. The distribution of bending moment and shearing force of the pile in new layout were more uniform than that of the traditional one,and their peak values also decreased,thus can make full use of the overall bearing capacity of the structure. In addition to shear-resist and bend-resist ability,the micropile can also play a axially resistant role,especially for the friction effect of consequent pile. With slope sliding,the tension of cable also increased gradually to share part of landslide load and utilize the bearing capacity of stable layer. Because of the active slide-resistant force of prestressed anchor,micropiles showed improved effect on the soil behind the micropiles. The results can provide theoretical references for design and application of the new structure.