浅埋大直径泥水盾构穿越上软下硬地层响应现场监测分析——以广花城际为例

Field monitoring analysis of ground response induced by a large-diameter slurry shield tunnelling through upper-soft lower-hard strata at shallow depth: A case study of the Guanghua Intercity Railway

  • 摘要: 浅埋大直径泥水盾构穿越上软下硬复合地层时,地层响应受掘进参数影响显著,变形控制难度大。为揭示盾构掘进对地层响应的影响特征,依托广花城际五工区始发段工程,布设3个监测断面,对地表位移、地层竖向位移、水平位移(测斜)及孔隙水压力进行现场监测。结果表明:在该类地层中进行掘进时扰动影响范围较大,地层响应呈显著阶段性和空间差异性,且因地层非均质性而呈现非对称分布;刀盘距离监测断面前约5环时,地层即出现可识别变形,穿越阶段响应最为剧烈,地层竖向位移表现为上部隆起、侧向外挤及非对称特征,地表位移由沉降转为隆起,呈“W”形分布,管片拼装与盾尾通过引起局部二次扰动,随后逐渐趋稳;孔隙水压力在穿越阶段呈两侧上升、中部下降的分布特征,随掘进与停机循环波动,注浆引发的超孔压消散存在滞后性;掘进参数变化对地层响应幅值与范围均有显著影响,推进速度较高时,断面地层变形幅值和扰动范围相对增大。

     

    Abstract: Shallow-buried large-diameter slurry shield tunnelling through upper-soft/lower-hard composite strata is highly sensitive to tunnelling parameters, making deformation control challenging. To investigate the characteristics of ground response induced by shield tunnelling, three monitoring sections were established in the launching section of Work Area 5 of the Guanghua Intercity Railway project, and field monitoring was conducted on surface displacement, subsurface vertical displacement, horizontal displacement (inclinometer), and pore water pressure. The results show that the disturbance influence zone is relatively large during tunnelling through such composite strata. The ground response exhibits distinct stage-dependent characteristics, spatial variability, and an asymmetric distribution due to stratum heterogeneity. Identifiable ground deformation was observed when the cutterhead was approximately five rings ahead of the monitoring section, and the most intense response occurred during the crossing stage. The subsurface vertical displacement was characterized by upper-layer heave, lateral outward displacement, and asymmetric distribution, while the surface displacement changed from settlement to heave and exhibited a W-shaped profile. Segment erection and shield tail passage induced local secondary disturbances, after which the ground response gradually stabilized. During the crossing stage, pore water pressure increased on both sides but decreased in the middle, and fluctuated cyclically with shield advance and stoppage. The dissipation of excess pore water pressure induced by grouting exhibited a lagging effect. Variations in tunnelling parameters significantly affected both the magnitude and extent of ground response, and higher advance rates resulted in greater deformation magnitude and a wider disturbance influence zone.

     

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