复合地层双线隧道盾构施工地表位移分析

Analysis of surface displacement in shield construction of double-line tunnels in composite ground

针对杭州地铁3号线某盾构区间上软下硬复合地层位移进行监测,并采用MIDAS/GTS软件模拟盾构开挖全过程,研究盾构开挖引起复合地层的地表位移分布规律,结果表明,单线隧道施工时,地表沉降大致符合Peck曲线分布,区间双线隧道轴线间距为2.77 D(隧道外径),导致双线施工完成后地表沉降呈现“W”型曲线分布;复合地层情况下地表沉降介于全部为硬层和软层之间。当软硬地层交界面位于隧道上方时,随着交界面的下移,最大沉降位移显著增大,表明地表沉降主要由上部地层的位移构成,上部地层的性质对地表位移影响显著。单线隧道施工时,距离隧道轴线1.5 D处的水平位移达最大,在距2.7 D处出现反弯点;双线隧道施工时,地表水平位移增大,峰值位移增大24%;后开挖隧道侧的峰值位移向后开挖侧移动2.6 D,先开挖隧道侧的峰值位移向后开挖侧略微移动,在双隧道中心处地层水平位移接近于0。

The displacement of the upper soft and lower hard composite ground during tunneling of a shield interval of Hangzhou Metro Line 3 was monitored.The MIDAS/GTS software was used to simulate the whole process of shield excavation,and the distribution of the surface displacement of the composite ground caused by shield excavation was studied.The results show that during the construction of the single-line tunnel,the surface settlement roughly conforms to the Peck curve distribution,and the axial spacing of the double-line tunnel in the interval is 2.77 D(where D is the outer diameter of the tunnel),resulting in the‘W’-shaped curve distribution of the surface settlement after the completion of the double-line construction.In the case of composite strata,the induced surface settlement is between complete the hard layers and soft layers.When the interface between soft and hard strata is located above the tunnel,the maximum settlement displacement increases significantly with the downward of the interface,indicating that the surface settlement is mainly generated by of the displacement of the upper strata,and the properties of the upper strata have a significant influence on the surface displacement.During the construction of single-line tunnel,the horizontal displacement at a distance of 1.5 D from the tunnel axis reaches the maximum value,and point of inflection occurs at a distance of 2.7 D.During the construction of the double-line tunnel,the horizontal displacement of the surface increases,and the peak displacement increases by 24%.The peak displacement of the post-excavation tunnel side moves 2.6 D to the post-excavation side.The peak displacement of the first excavation tunnel side moves slightly to the post-excavation side,and the horizontal displacement of the stratum is close to 0 at the center of the double tunnels.