超大断面公路隧道围岩变形及荷载释放率研究

Study on surrounding rock's deformation and load release rate of super-section highway tunnel

超大断面隧道群多修建于山区,地质条件复杂且施工风险高、难度系数大,对其围岩变形及荷载释放率的研究可为此类工程的安全施工提供理论依据。文章依托济南绕城高速、京沪高速济南连接线龙鼎隧道工程,采用有限元数值仿真技术,分析了裂隙密集带对超大断面隧道围岩变形和塑性区分布的影响,研究了半步CD法施工隧道围岩空间荷载释放演化规律。结果表明:半步CD法施工超大断面Ⅳ级围岩隧道拱顶变形较大,但围岩位移在可控范围内;裂隙密集带对超大断面隧道围岩稳定性影响显著,其区域围岩塑性区和位移均处于最大状态;掌子面后方的较安全距离最小为5 m,而安全距离则应>10 m。

Most super-section highway tunnel groups are built in mountainous area with complicated geological conditions, their construction risk is high and difficulty is very big. The study on surrounding rock＇s deformation and stability can provide the basis for the safety construction of other similar super-section highway tunnels. Under the background of Long Ding super-section highway tunnel,which belongs to Jinan round-city highway and connection highway of Beijing and Shanghai,using the numerical simulation in this paper,tunnel＇s surrounding rock＇s displacements and plastic zones affected by fissure concentration zones were analyzed,the evolution law of surrounding rock＇s load release under the half-step CD method construction was studied. Results show that,Ⅳ level surrounding rock＇s tunnel vault has larger deformation under half-step CD method construction,but still under control; fissure concentration zones have big influence on the stability of super-section tunnel＇s surrounding rock,where the plastic zones and displacements are both in the maximum state;the minimum safe distance in the rear of the palm is 5 meters,for higher safety degree,the distance is10 meters at least.