盾构刀具分层与切削参数对空心管桩破碎机理的影响

Influence of Shield Cutter Layered Configuration and Cutting Parameters on the Fracture Mechanism of Hollow Pipe Piles

  • 摘要: 为探究盾构刀具切削作用下空心钢筋混凝土管桩的动态损伤破碎过程,以宁波地铁7号线盾构隧道为工程背景,建立盾构刀具分层切削钢筋混凝土管桩动力学模型,探究刀具分层配置和切削参数对切削效果的影响。研究结果表明:(1)当刀具采用分层配置时,第一层撕裂刀局部破碎混凝土,并且有效切断钢筋笼。当刀具采用均一高差配置时,空心管桩中间位置出现贯通裂纹,且裂纹扩展为大范围断裂,钢筋笼因失去约束而变形,不能被有效切断。(2)刀具切削第一根主筋时,钢筋笼受较为完整的混凝土约束,瞬时冲击荷载最大,为最不利工况。刀具采用分层配置时的冲击荷载峰值远小于刀具采用均一高差配置时的峰值。(3)随着切削速度的增大,冲击荷载峰值显著增大,这是混凝土的应变率效应导致的。贯入度增大将导致切削荷载整体处于较高水平,但是对冲击荷载峰值的影响相对较小,这是由于钢筋直径较小,均在一次切削中完全断裂。(4)工程实践表明,当刀盘转速维持在0.9 r/min,贯入度维持在20~40 mm/r时,切桩过程中推力在15 500 kN附近波动,峰值仅有18 000 kN,扭矩保持在800 kN·m附近。

     

    Abstract: To explore the dynamic damage and fracture process of hollow reinforced concrete pipe piles under the cutting action of shield cutters, a dynamic model for shield cutter groups cutting reinforced concrete pipe piles is established with the Ningbo Metro Line 7 tunnel project as the engineering background. The effect of cutter layered configuration and cutting parameters on cutting performance is investigated. The research results show: (1) When cutters are arranged in layers, the first layer rippers locally fracture the concrete and effectively cut the reinforcement cage. When cutters are arranged with uniform high difference configuration, a penetrating crack appears at the middle of the hollow pipe pile, and the cracking expands into a large-scale fracture, causing the reinforcement cage to lose its constraint and deform, which cannot be effectively cut. (2) When the cutter cuts the first main reinforcement, the reinforcement cage is constrained by the relatively intact concrete, and the instantaneous impact load is the largest, which represents the most unfavorable condition. The impact load peak for the layered cutter configura? tion is much smaller than that for the uniform high difference configuration. (3) As the cutting speed increases, the peak impact load increases significantly due to the strain rate effect of the concrete. The increase in penetration leads to an overall higher cutting load, but the impact on the peak impact load is relatively small, as the rebar diameter is small and breaks completely in a single cut. (4) Engineering practice shows that when the cutter head rotation speed is maintained at 0.9 r/min and the penetration is maintained between 20~40 mm/r, the thrust during the cutting process fluctuates around 15 500 kN, with a peak value of only 18 000 kN, and the torque remains around 800 kN·m.

     

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