地铁车站PBA法导洞施工诱发地表沉降规律研究

以长春地区土岩复合地层条件下地铁自由大路车站工程为依托,对地铁车站PBA法导洞施工引起地表沉降规律进行了分析。研究结果表明:(1)车站主体双层暗挖导洞施工引起的地表累计沉降量占车站施工最终沉降量的一半以上,约53.46%,地表沉降槽曲线为"单峰"形态,横向影响范围约50 m左右。(2)导洞施工诱发地表沉降分为初期沉降、快速沉降及沉降收敛3个阶段,初期阶段沉降4 mm左右,占14.81%,快速阶段沉降20 mm左右,占74.07%,收敛阶段沉降3 mm左右,占11.11%,隧道施工过程须重点监测掌子面靠近监测断面6 m与远离监测断面15 m的施工段。(3)开挖顺序与开挖进尺对地表沉降影响较大,选择先上后下,先边洞后中洞的开挖顺序最为合适,开挖进尺控制在0.1L~0.14L(L为洞跨)为宜。

Study on Surface Settlement of Subway Station induced by PBA Construction Method

The paper attempts to research surface subsidence in compound stratum caused by PBA method which was adopted in the construction of the Freedom Parkway subway station of Changchun.The researching results show:(1) construction of double-layer undermining entering hole in the subway main body causes surface accounted for more than half of the final settlement station construction,about 53.46％.Curve of surface subsidence presents a "uni-modal" form,whose lateral affected area is about 50 meters.(2) Surface subsidence can be divided into three stage:early subsidence stage,rapid subsidence stage and settlement convergence stage.The three-stage settlement each accounts for 14.81％,74.07％,11.11％,respectively.Subsidence monitoring in construction process should focus on the tunnel face which is near the cross section of 8 m and away from the monitoring section of 15 m.(3) Excavation sequence progress are key factors to surface subsidence.Its better to excavate from top to bottom and form side hole to central hole,and excavation progress should be best control in 0.1L to 0.14L (L is the hole cross).