砾砂地层盾构切削大直径群桩的刀具研究

Shield cutter for cutting large diameter group piles in gravel stratum

刀盘刀具是盾构机实现切削功能并保证其顺利推进的主要部件,合适的刀具选型与设计在保证盾构机成功切削大直径钢筋混凝土群桩的过程中至关重要。依托沈阳地铁4号线盾构切桩工程,结合盾构穿越砾砂地层的工程特点以及切削大直径钢筋混凝土群桩的工程需求,对刀盘刀具进行选型,采用LS-DYNA软件模拟不同刃宽、刃角及前角的贝壳刀切削钢筋的效果。将分析结果应用于该工程,通过对比切桩前后既有隧道沉降变化规律论证刀具选型设计的合理性,并根据切桩后的贝壳刀磨损规律及盾构机排出钢筋情况,评估刀盘刀具切削效果,从而优化刀盘的刀具布置。研究结果表明:盾构刀盘采用面板+辐条复合式直角刀盘,切桩刀具采用前角-45°零后角、5 mm刃宽、90°刃角的双面刃贝壳刀,可提升盾构切桩效果;盾构切桩过程中既有隧道的变形波动控制在1.1 mm内,切桩完成后既有隧道的最大沉降仅为1.96 mm,未对既有隧道造成明显影响;刀盘布置贝壳刀时,应增加高度为210 mm的贝壳刀数量,尤其需要避免单个辐条上仅有1把高度为210 mm贝壳刀的情况,可有效提高刀盘刀具切削钢筋的能力并降低崩刃风险。刀具选型设计结果成功应用于沈阳地铁4号线切桩工程,可为今后类似工程提供参考。

The cutter is the main component of the shield for cutting and advancement.Suitable selection and design of cutter are essential in ensuring to the successful cutting of large diameter reinforced concrete group piles.Based on the Shenyang Metro Line 4 project,the cutters were selected based on the engineering characteristics of the shield crossing the gravel stratum and the need to cut large diameter reinforced concrete group piles.The software LS-DYNA was used to simulate the effect of shell cutters on cutting rebars with different blade widths,blade angles and rake angles.The results of analysis were applied to this project.The appropriateness of the cutter selection and design was validated by comparing the settlement variations of the existing tunnels.By analyzing the wear characteristics of the cutters and the discharge of the rebars after cutting,the cutting effect was evaluated,and then the cutters arrangement of the cutterhead was optimized.The results show that the shield cutting effect can be improved by using a panel and spoke composite right-angle cutterhead,and a double-sided blade shell cutter with rake angle of−45°and zero rear angle,5 mm blade width,90°blade angle.The deformation fluctuation of the existing tunnel during the shield pile cutting process is controlled within 1.1 mm.The maximum settlement of the existing tunnel after crossing is only 1.96 mm.This does not have any significant impact on the existing tunnel.When using shell cutters,the increasing number of 210 mm shell cutters is able to improve the cutting capacity of the cutter and reduce the risk of chipping,especially for spokes with only one leading cutter.The results of the cutter selection design are successfully applied to the Shenyang Metro Line 4 pile cutting project,which can serve as a reference for similar projects in the future.