14.93m泥水平衡盾构施工扰动实测研究

A Field Research of Ground Disturbance by 14.93 m Slurry Balance Shield Construction

利用现场监测数据研究14.93 m泥水平衡盾构施工诱发的地层扰动的程度、波及范围和持续时间。监测项目包括5根测斜管、9个地表沉降监测点和20个侧向土压力传感器,监测持续45 d。将采集到的测斜数据和深层水土压力数据绘制成云图,结合地表沉降曲线分析表明:盾构正面支护性能优良,盾构切口通过前后地层几乎没有产生位移,盾构底面以下侧向应力扰动度<10%。盾尾脱出及其后一环脱出是地层扰动最剧烈的时刻,隧道开挖卸载造成了底面以下2D×1.5D(D是隧道直径)范围内应力扰动>10%;采用127%的同步注浆率造成了隧道周边土体的向外挤压和地表隆起,土层最大水平位移位于盾构肩部和腰部注浆孔之间,最大位移19.7 mm,距离盾构轴线2.5D范围以外的位移<2 mm;地面隆起最大值41.3 mm,距离盾构轴线外侧1.5D以外的位移<4 mm。盾构远离监测断面30 d后,地面隆起回落57%。

Ground disturbance magnitude,sweep region and duration induced by a 14.93 m slurry shield construction are researched based on the in-situ monitoring data.The in-situ monitoring system includes 5 inclination pipes,9 ground surface settlement points and 20 horizontal earth pressure sensors and the period of 45 d.Contour maps are drawn based on the inclination and horizontal earth pressure data.Combined with ground surface settlement curve analysis,the results can show that the 14.93 m slurry shield has an excellent cutting head supporting performance.Ground movement can hardly be observed during cutting head crossing the monitoring section,and the horizontal earth pressure disturbance degree<10%.In the stage of lining ring being pushed out of the shield tail,the most severe disturbance is observed,and the area of disturbance degree>10% is 2 D×1.5 D(D represents the tunnel diameter) approximately.A synchronic grouting rate of 127% caused extrusion effect to the soil around tunnel.A maximum horizontal displacement of 19.7 mm located between the upper two grouting nozzles(shoulder and waist) is observed,and decreased to less than 2 mm 2.5 D far away from the tunnel axis.Maximum ground surface heave of 41.3 mm is observed at tunnel axis,and the heave displacement decreased to less than 4 mm 1.5 D far away from the tunnel axis.After 30 d,the shield going far away from the monitoring section,the ground surface heave displacement is reduced to 57% of the peak value.