大断面矿山法隧道开挖对小净距盾构隧道的影响分析

Analysis of Large Section Mining Excavation Impact on Shield Tunnel with Small Interval

以厦门地铁1号线集美中心站站后停车线隧道工程为背景,采用FLAC3D三维有限差分软件,对此大断面矿山法隧道开挖对小净距盾构隧道的影响进行了三维数值分析。分析了CRD(交叉中隔墙)四步开挖法、CRD六步开挖法(靠近盾构隧道部分后开挖)及CRD六步开挖法(靠近盾构隧道部分先开挖)对盾构隧道的影响,揭示了盾构隧道位移和管片弯矩的变化规律:大断面矿山法隧道开挖时对先施工的小净距盾构隧道产生4~9 mm的位移值,盾构管片产生80~170 kN·m的弯矩值。另外,CRD四步开挖对盾构隧道不利,盾构隧道的位移和弯矩分别增大约33%和6%,并且靠近盾构隧道的部分对盾构扰动更大,因此,推荐使用CRD六步开挖法(靠近盾构隧道部分后开挖)。最后对比分析了盾构隧道的现场监测位移值和数值模拟结果。

In the background of the tunnel project behind Jimei Center Station on Xiamen metro Line 1,a 3 D numerical simulation of the impact of large section mining method excavation on shield tunnel with small interval is conducted by means of the finite element program FLAC3 D.The impacts of the center cross diagram(CRD)four-step excavation method,the CRD six-step excavation method(later excavation near the shield tunnel)and the CRD six-step excavation(first excavation near the shield tunnel)on the shield tunnel are analyzed,the variation law of shield tunnel displacement and bending moment of the segment is revealed.The large-section tunnel excavation with mining method will generate 4~9 mm displacement relative to the previously constructed shield tunnel with small interval,and 80~170 kN·m bending moment to the segment of the shield tunnel.In addition,the four-step excavation is unfavorable to the shield tunnel,because the displacement and the bending moment of the shield tunnel will increase by 33%and 6%respectively,and the part near the shield tunnel will disturb the shield even greater.Therefore,the CRD six-step excavation of(later excavation near the shield tunnel)is recommended.Finally,the displacements obtained by the on-site monitoring and numerical simulation are compared and analyzed.