地铁盾构隧道施工对地表沉降的影响分析

Analysis of the Influence of Subway Shield Tunnel Construction on Surface Settlement

以郑州市轨道交通5号线某区间盾构隧道开挖工程为例,采用FLAC3D数值模拟软件进行建模分析,将数值模拟软件得出的隧道开挖引起的地表沉降值与实际测量的数值进行对比,得到以下结论:隧道拱顶处沉降最大,拱底处隆起最大;研究断面的横向沉降均呈W形分布;断面一地表最大横向沉降值为14.6 mm,对应的数值模拟得到的最大横向沉降值为14.2 mm;断面二地表最大横向沉降值为7.6 mm,对应数值模拟得到的最大横向沉降值为7.2 mm,可知横断面沉降的实测值和数值模拟值吻合度较好,说明数值结果比较可靠。对于地表纵向沉降,开挖过程中,掌子面前方一定距离处地表形成隆起,这与盾构机与土体之间的摩擦有关,在开挖之后距离掌子面20 m左右地表沉降基本趋于平稳,左右线的实测值与数值模拟值吻合度良好。断面二隧道穿越的粉质黏土厚度比较大,且自稳性较好,故断面二沉降要小于断面一的沉降,因此隧道开挖面处的地层特性对盾构开挖的稳定性十分重要。

Taking the shield tunnel excavation of a subway project of Zhengzhou Metro Line 5 as an example,a large-scale numerical simulation software FLAC3D was used for modeling and analysis,the surface settlement caused by tunnel excavation obtained by numerical simulation software is compared with the actual measured value,the following conclusions were obtained:the settlement at the crown of the tunnel is the largest,the arch of the bottom bulge is the largest;the lateral settlement of the study section presents a“W”type distribution;the maximum lateral settlement value of a section surface is 14.6 mm,and the corresponding numerical simulation results show that the maximum lateral settlement value is 14.2 mm;the maximum lateral settlement of the second cross-section surface is 7.6 mm,and the maximum lateral settlement obtained by numerical simulation is 7.2 mm,it can be seen that the measured value of cross-section settlement is in good agreement with the numerical simulation value,indicating that the numerical results are reliable.For the longitudinal settlement of the ground surface,during the excavation process,the ground surface rises at a certain distance in front of the tunnel face,which is related to the friction between the shield machine and the soil,after excavation,the ground settlement around 20 m from the palm face is basically stable,and the left and right lines are measured the value agrees well with the numerical simulation value.Compared with Section 1,the thickness of the silty clay traversed by Section 2 tunnel is relatively large,and the self-stability is good.Therefore,the settlement of Section 2 is smaller than that of Section 1.Therefore,the characteristics of the stratum at the tunnel excavation surface are very important to the stability of shield excavation.