姿态偏转引起的复合地层双模盾构卡机事故

双模盾构在复合地层中掘进时，刀具损耗及异常磨损的频率提升，盾构掘进姿态难以控制。最终导致隧道开挖直径减小，引发卡机事故。为了分析盾构姿态偏转及扩挖间隙纵向非均匀分布对盾壳受力特征的影响，本文依托深圳地铁13号线白应区间，利用FLAC3D计算了盾构在掘进时所受的围岩压力，研究结果表明：(1)卡机断面处边滚刀发生了严重的磨损和偏磨，最大磨损量为25 mm。复合地层中掘进参数出现明显波动，盾构更易发生向上的偏转；(2)上软下硬复合地层中，盾壳上部所受的围岩压力较大，地层交界位置出现应力集中现象。盾构姿态偏转时，盾壳前端应力的增长相较盾尾更为显著。盾构向一侧偏转时，相应位置盾壳承受的法向应力增加；(3)盾构姿态向上偏转相较于向下偏转更易引起卡机事故。当偏转角大于±0.5°时，盾壳所受摩阻力迅速增加，在盾构掘进时应尽可能保证盾构处于水平，或小角度下倾姿态。

Analysis on the Attitude Deflection Induced Jamming Accident of the Dual-Mode Shield in Composite Strata

When excavating in composite strata, the wear rate of the disc-cutters and the frequency of abnormal wear will significantly increase. Therefore, the overcut clearance is accordingly reduced, which results in the occurrence of shield jamming accidents. In order to analyze the influence of shield attitude deflection and longitudinal non-uniform distributed overcut on the mechanical properties of shell, based on Baiying section on Shenzhen metro line 13, the rock pressure exerting on shield machine during construction stage was calculated by FLAC3D. The results indicate that (1) severe eccentric wear occurred at the jamming section. The maximum wear reaches 25 mm. The operational parameters encounter obvious fluctuation in composite strata. The shield machine has a higher tendency to deflect upwards. (2) In upper soft and lower hard strata, the rock pressure borne by the upper part of the shield shell is larger than which on the lower part. The stress concentration occurs at the interface between the strata. The stress at front of the shield shell grows more significantly, compared with which at the shield tail. The normal pressure at the tunnel vault and invert respectively increases, when the shield deflects upward and downward. (3) The upward deflection is more likely to cause jamming accident compared to the downward deflection. The friction suffered by shield shell rises rapidly when the deflection angle exceeds ±0.5°. During shield tunneling, the shield machine should maintain a horizontal or small angle downward deflection state as far as possible.