SURFACE SETTLEMENT ANALYSIS OF SHIELD PASSING THROUGH POWER TUNNEL AND DIRECTLY CUTTING PILE FOUNDATION OF HANGZHOU METRO LINE 4
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摘要: 以杭州地铁4号线盾构下穿电力隧道切削桩基工程项目为背景，结合三维数值模拟和实测沉降数据进行分析，研究盾构下穿电力隧道切削桩基对地表的沉降影响，并以掌子面推进力、同步注浆压力为施工参数进行数值分析。数值模拟数据表明：切桩期间地表的沉降量大且沉降速率快，沉降量及沉降速率均随监测点离隧道轴线距离的增大而减小，由于电力隧道结构的特殊性，切桩过程中产生的沉降量占总沉降量比重较小。掌子面推进力的变化对切桩前地表的隆起影响较为显著，对切桩时地表产生的沉降量影响相对较小；注浆压力的变化对切桩前地表的隆起和切桩时产生的沉降量影响均不够显著。通过比较实测数据与模拟数据发现，实测数据中由于切桩产生的地表沉降有一定的滞后性。根据数值模拟结果，建议在施工过程中当盾构机与桩基础的距离大于6 m时，适当增加掌子面推力以减小地表的最终沉降；距离小于6 m时，恢复掌子面推力为1倍静止土压力，以减小桩身水平位移确保切桩工作顺利进行。Abstract: As the background of Hangzhou Metro Line 4 shield passing through a power tunnel, the influence of the shield directly cutting pile foundation on surface settlement is studied through three-dimensional numerical simulation. The thrust force of palm face and synchronous grouting pressure are used as tunneling parameters for numerical simulation, and field monitoring data is obtained and analyzed. The simulation data confirm that: the surface settlement is large and the settlement rate is fast during the pile cutting period, and both the settlement amount and the settlement rate decrease with the increase of the distance between the monitoring point and the tunnel axis. Due to the particularity of the structure of the power tunnel, the settlement generated in pile cutting process accounts for a small proportion of the total settlement. The thrust force of the palm face has a great influence on the heaves of the surface before pile cutting and less on the surface settlement amount during pile cutting. The grouting pressure has little effect on the heaves of the surface before pile cutting and the surface settlement amount during pile cutting. By comparing the field data with the simulated data, it is found that the surface settlement caused by pile cutting has a certain lag in the field data. According to the numerical simulation results, it is suggested that when the distance between shield machine and pile foundation is greater than 6 m in the construction process, the thrust of the palm face should be appropriately increased to reduce the final settlement of the surface. When the distance is less than 6 m, the thrust should be adjusted back to 100% static earth pressure to reduce the horizontal displacement of the pile and to ensure the smooth operation of pile cutting.
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Key words:
- shield method /
- cut pile foundation /
- settlement /
- numerical simulation /
- thrust force of the palm face
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图 1 左线切削穿越2根Φ600 mm减沉桩示意图
Figure 1. The left line directly cutting 2 Φ600 mm reduction piles schematic
图 7 监测点DBC44模拟实测对比图
Figure 7. Simulation and measured comparison of DBC44 monitoring point
图 8 监测点DBC45模拟实测对比图
Figure 8. Simulation and measured comparison of DBC45 monitoring point
图 9 监测点DBC46模拟实测对比图
Figure 9. Simulation and measured comparison of DBC46 monitoring point
图 10 监测点DBC47模拟实测对比图
Figure 10. Simulation and measured comparison of DBC47 monitoring point
图 11 地表最终沉降曲线图(注浆压力0.30 MPa)
Figure 11. Surface final settlement curve (grouting pressure is 0.30 MPa)
图 12 地表最终沉降曲线图(注浆压力0.32 MPa)
Figure 12. Surface final settlement curve (grouting pressure is 0.32 MPa)
图 13 地表最终沉降曲线图(注浆压力0.34 MPa)
Figure 13. Surface final settlement curve (grouting pressure is 0.34 MPa)
图 14 DBC44全过程沉降图(注浆压力0.30 MPa)
Figure 14. Settlement curve of DBC44 (grouting pressure is 0.30 MPa)
图 15 地表最终沉降曲线图(推力1.0E0)
Figure 15. (thrust of palm face is 1.0E0) Surface final settlement curve
图 16 地表最终沉降曲线图(推力1.15E0)
Figure 16. (thrust of palm face is 1.15E0) Surface final settlement curve
图 17 地表最终沉降曲线图(推力1.3E0)
Figure 17. (thrust of palm face is 1.3E0) Surface final settlement curve
图 18 DBC44全过程沉降图(推力1.0E0)
Figure 18. Settlement curve of DBC44 (thrust of palm face is 1.0E0)
图 19 右线掘进完成时地表变形图
Figure 19. Surface deformation diagram after completion of right line excavation
图 20 左线掘进完成时地表变形图
Figure 20. Surface deformation diagram after completion of left line excavation
图 21 各工况下桩身水平位移图
Figure 21. Horizontal displacement diagram of pile under various working conditions
表 1 土层物理性质参数表
Table 1. Physical properties of the soil
名称 静止侧压力系数K0 重度/(kN/m3) 层厚/m 压缩模量/MPa 泊松比 粘聚力/kPa 摩擦角/(°) 1-2素填土 0.50 18.6 1.25 1.80 0.33 10.0 12.0 2-2粉质粘土 0.56 18.9 1.61 1.80 0.36 17.0 14.5 5-2黏土 0.45 19.5 5.40 4.92 0.31 35.0 16.0 5-3砂质粘土夹粉土 0.53 18.8 8.20 2.37 0.35 17.0 19.0 7-1黏土 0.45 19.7 8.70 5.85 0.31 40.0 15.0 7-2粉质黏土 0.45 20.0 7.84 4.38 0.31 30.0 18.0 
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