高地应力软岩隧道施工动态控制与优化研究

Research on Construction Dynamic Control and Optimization of a Tunnel in Soft Rock under High In-situ Stresses

根据兰渝铁路毛羽山隧道出口开挖过程中出现严重大变形的工程实例,利用FLAC3D建立三维数值模型,对不同台阶长度、仰拱闭合时机、锚杆长度以及二次衬砌浇筑时机的隧道施工进行了动态模拟。计算结果表明:台阶长度对大变形控制至关重要,应尽可能减小上台阶长度,采用超短台阶法施工;仰拱对于挤压性围岩隧道大变形控制具有显著的效果,应尽早封闭成环;随着锚杆长度的增加,隧道变形逐渐减小,但是当其长度大于8m时,再增加锚杆长度对控制大变形所起作用不明显;开挖后立即施作二次衬砌,可有效控制围岩蠕变变形。

Large deformations occurred during the construction of Maoyushan tunnel exit on Lanzhou-Chongqing Railway.A three-dimensional numerical model with FLAC3D was established to simulate tunnel construction with various bench lengths,closure time of invert,anchor lengths and casting time of secondary lining.Results indicated that the bench length was the key to control deformation,and the upper bench length should be shortened as much as possible;invert played a significant role to control deformation in squeezing rocks and it should be closed as early as possible;tunnel deformations gradually decreased with the increase of anchor lengths up to 8m;and secondary lining should be cast promptly after excavation to effectively control the creep deformation of surrounding rocks.