螺旋钢桩加固边坡抗滑承载特性研究

Study on anti-sliding bearing characteristics of slope reinforced by spiral steel piles

目前,针对螺旋钢桩加固边坡问题,其桩土作用机制及抗滑承载特性研究较少,限制其推广应用。因此,基于FEM和桩与边坡解耦设计分析方法,提出一种适用于螺旋钢桩加固边坡模型的简化方法,并对简化模型桩-土相互作用的模拟效果和抗滑力计算准确度进行验证,随后分别建立螺旋钢桩和等直径钢管桩有限元模型,对比分析其各项受力性能,揭示螺旋钢桩的受力模式。研究结果表明:通过该简化方法计算出的桩顶位移值与现场实测值、滑面处弯矩峰值结果相差均在10%之内,在产生相同抗滑力下,简化模型与三维桩土模型的桩顶位移差值在5%以内,说明此简化方法模拟精度可满足要求。在抗滑承载特性方面,当桩顶产生5 cm位移时,螺旋钢桩较圆型桩抗滑力提高15%;产生相同的抗滑力时,螺旋钢桩顶位移较圆型桩顶位移减少22%。螺旋钢桩在承受滑坡推力时,首先通过桩身挠曲抵抗滑坡推力,随着滑坡位移不断增大,螺旋叶片与周围土体产生的摩擦和挤压作用不断增强,处于滑动剪切区的叶片发生翘曲变形,通过形成反弯矩作用抵抗滑坡推力。平行滑动区与锚固区的叶片在轴向产生相对位移,调动螺旋叶片产生端阻力,并将其传递至滑面以增大抗滑力,由此改变桩周土体位移场与应力场的分布,增强桩土协同工作能力,并起到良好的应力扩散与传递作用。研究成果可为螺旋钢桩的承载特性计算与加固设计提供借鉴。

At present,studies on the pile-soil mechanism and anti-sliding bearing characteristics of spiral steel piles for slope reinforcement are rare,which limits their popularization and application.Therefore,based on the FEM and the pile-slope decoupling design analysis method,a simplified method suitable for slope models reinforced with spiral steel piles was proposed,and the simulation effects of the simplified model pile-soil interaction and the accuracy of the anti-sliding force calculation were verified.Then,finite element models of spiral steel piles and equal-diameter steel pipe piles were established,and their mechanical properties were compared and analyzed to reveal the stress mode of spiral steel piles.The results show that the difference between the displacement value of the pile top calculated by the simplified method and the field measured value and the peak value of the bending moment at the sliding surface is within 10%.Moreover,under the same anti-sliding force,the displacement difference between the simplified model and the three-dimensional pile-soil model is within 5%,indicating that the simulation accuracy of this simplified method can meet the requirements.In terms of the anti-sliding bearing characteristics,when the pile top experiences 5 cm of displacement,the anti-sliding force of the spiral steel pile is 15%greater than that of the circular pile.When the same antisiding force is generated,the displacement of the spiral steel pile top is 22%less than that of the circular pile top.When the spiral steel pile bears the thrust of the landslide,it first resists the thrust of the landslide through the deflection of the pile body.The friction and extrusion between the spiral blade and the surrounding soil are continuously enhanced with increasing displacement of the landslide.The blade in the sliding shear zone warps and deforms to resist the thrust of the landslide by forming a reverse bending moment.The blades in the parallel sliding zone and the anchorage zone undergo relative displacement in the axial direction,which mobilizes the spiral blades to generate end resistance and transfer it to the sliding surface to increase the anti-sliding force,thus changing the distribution of displacement field and stress field of soil around the pile,enhancing the cooperative working ability of the pile and soil,and playing a good role in stress diffusion and transfer.The research results can provide a reference for the calculation of bearing characteristics and reinforcement design of spiral steel piles.