Based on a cross-river tunnel of Wuhan Metro Line 8, we present a two-dimensional discrete element model for shield attitude adjustment considering the effect of overbreak cutters. The shield shell mechanics under the influence of over-excavation rate, over-excavation orientations, and overburden load are simulated, and the tunneling mechanics law and the ultimate range during the adjustment of the shield attitude are investigated. The simulation results indicate the following: (1) The greater the over-excavation rate, the smaller the force exerted by the soil layer in the negative direction of the shield movement; therefore, increasing the over-excavation rate is helpful in expanding the range of shield attitude adjustment. (2) The shield is stressed symmetrically while conducting positive and negative horizontal adjustments in the soil layer, which has a symmetrical distribution, but vertical upward adjustment is more difficult than vertical downward adjustment. (3) With the increase in overburden load, the space of the shield attitude adjustment is gradually reduced at the same over-excavation rate. A good engineering application was achieved in this project using the simulation model. It is recommended to use the attitude adjustment method by controlling the tunneling parameters. In difficult situations such as high overlying loads, the over-excavation cutter can be used to assist in adjusting the shield attitude.

以武汉地铁8号线某跨江隧道为背景，提出了考虑超挖刀影响的盾构姿态调整二维离散元模型。对超挖率、超挖方位和覆土荷载影响下的盾构壳力学进行了模拟，研究了盾构姿态调整过程中的掘进力学规律和极限范围。仿真结果表明： (1) 超挖率越大，土层对盾构运动负方向的作用力越小；因此，提高超挖率有助于扩大盾构姿态调整范围。(2)盾构在土层中进行正反水平调整时对称受力，呈对称分布，但垂直向上调整比垂直向下调整困难。(3) 随着覆土荷载的增加，在相同的超挖率下，盾构姿态调整空间逐渐减小。该仿真模型在本项目中取得了良好的工程应用。推荐使用通过控制隧道参数的姿态调整方法。在高覆载等困难情况下，可采用超挖刀辅助调整盾构姿态。该仿真模型在本项目中取得了良好的工程应用。推荐使用通过控制隧道参数的姿态调整方法。在高覆载等困难情况下，可采用超挖刀辅助调整盾构姿态。该仿真模型在本项目中取得了良好的工程应用。推荐使用通过控制隧道参数的姿态调整方法。在高覆载等困难情况下，可采用超挖刀辅助调整盾构姿态。