双线隧道下穿施工对铁路路基沉降影响数值分析

Existing Railway Caused by Underpass Construction of Double Track Subway Tunnel Numerical Analysis of Subgrade Settlement Law

随着山区城市轨道交通快速发展,轨道交通区间隧道下穿既有铁路工程越来越多。由于山区城市特殊的地质条件和周边复杂环境,区间隧道布置受到限制,左右线隧道水平距离较近。与单线隧道施工比较,双线隧道施工引起既有铁路路基沉降更为复杂。左右线隧道的水平距离对下穿既有铁路引起铁路路基沉降影响规律尚不清楚,还需进一步研究。依托山地城市贵阳轨道交通3号线区间隧道下穿既有铁路工程,建立三维数值模型,分析铁路路基沉降特点,研究不同水平间距双线隧道下穿施工引起既有铁路路基的沉降变形规律。研究发现随着双线隧道水平间距减小,沉降槽范围增大,铁路路基最大沉降值逐渐增大。随着双线隧道水平间距增加,铁路路基沉降最大值位置由隧道中心线对应路基向左线隧道、右线隧道中心线相对应的路基位置转移,路基横向沉降曲线呈V型-U型-W型变化。当隧道水平间距小于15 m时,路基横向沉降曲线呈V型,应加强支护措施,减小后行隧道施工对既有铁路路基沉降产生的叠加效应,将铁路路基沉降控制在允许范围。

With the rapid development of urban rail transit in mountainous areas,there are more and more rail transit tunnels crossing under existing railways.Due to the special geological conditions and complex surrounding environment of mountainous cities,the layout of section tunnels is limited and the horizontal distance between left and right tunnels is relatively close.Compared with single track tunnel construction,the settlement of existing railway subgrade caused by double track tunnel construction is more complex.The influence of the horizontal distance of the left and right tunnels on the railway subgrade settlement is still unclear,and further research is needed.Relying on Rail Transit Line 3 interval tunnel undercrossing the existing railway project in the mountainous city Guiyang,a three-dimensional numerical model was established,the characteristics of railway subgrade settlement were analyzed,and the settlement deformation law of the existing railway subgrade was studied.It is found thatthe maximum settlement of railway subgrade increases with the decrease of horizontal spacing of double track tunnels,and the settlement trough range also increases.With the increase of the horizontal spacing of double track tunnels,the position of the maximum railway subgrade settlement is transferred from the center line of the line tunnel corresponding to the subgrades to the left line tunnel and the right line tunnel,and the lateral subgrade settlement curve changes the patterns of V-U-W-shape.When the horizontal spacing of tunnels is less than 15 m,the lateral settlement curve of the subgrade is V-shaped,in which the support measures should be strengthened to reduce the superposition effect of the tunnel construction behind on the existing railway subgrade settlement,and the railway subgrade settlement should be controlled within the allowable range.