基于PFC3D的北京砂卵石地层盾构刀盘选型及刀具布置数值模拟研究

砂卵石地层是一种典型的力学不稳定地层及强磨蚀性地层，盾构在该类地层中掘进通常会面临刀盘、刀具磨损严重，盾构推力与刀盘扭矩偏高且波动幅度大、地层变形不易控制等问题。砂卵石地层盾构掘进效率的高低及地层控制的好坏，刀盘选型及刀具配置是关键。以北京地铁新机场线“磁各庄站～1#风井”盾构区间为工程依托，利用PFC3D数值模拟及现场测试相结合的手段，研究刀盘开口率、刀具组合高差、先行刀刀间距等参数对盾构掘进效率及地层变形的影响。研究结果表明：相同掘进参数下大开口率辐条式刀盘比小开口率辐板式刀盘具有更好的掘进速度，小开口率辐板式刀盘掘进时引起的地表变形更小，对周围地层的扰动范围也更小；先行刀与切削刀的组合高差为70 mm时盾构掘进效率较高且扭矩较低；先行刀刀间距设定为300 mm时，盾构有较好的掘进效率和较低的刀盘扭矩。工程实践表明；要实现砂卵石地层盾构长距离高效掘进，大开口率辐条式刀盘设计及大高差梯次化刀具布置是基础，高贯入度、低转速的掘进控制是关键。研究结果可为类似工程的盾构刀盘选型与刀具布设提供借鉴。

Numerical Simulation of the Type Selection of Cutterhead Selection and Tool Arrangement in Beijing Sandy Pebble Stratum Based on PFC3D

Various difficulties are encountered in sand-pebble strata, which are typically mechanically unstable, and serious tool wear has been experienced during shield tunneling. The cutterhead selection and tool arrangement are the key to realize the long-distance and efficient shield driving in sand-pebble strata. Taking second section of the Beijing New Airport line tunneling project as background, this paper studied the influence of parameters such as cutterhead aperture ratio, tool combination height difference, and cutter spacing on shield tunneling efficiency and formation deformation by PFC3D and field test. The results show that the driving speed under the spoke-type cutterhead is better than that under the panel-type cutterhead for the same tunneling parameters, while surface deformation and disturbance range to the surrounding strata are less under the panel-type cutterhead with the small cutterhead aperture ratio; When the height difference between the ripper and the scraper is 70 mm, the shield tunneling efficiency is higher and the cutterhead torque is lower; when the ripper spacing is 300 mm, the shield tunneling efficiency is better and the cutterhead torque is lower. Engineering practice shows that the spoke-type cutterhead with large aperture ratio and multidimensional configuration method for cutting tools are the foundation to realize the long-distance shield driving, and the tunneling parameter control with high penetration and low speed is the key. The results of this study provide a theoretical reference for cutterhead selection and tool arrangement in shield construction under similar projects.