地形偏压隧道开挖变形特征及预加固措施

Deformation Behavior of Topographic Unsymmetrical Loaded Tunnel after Excavation and Its Pre-reinforcement

在全面考虑了偏压隧道影响因素的基础上,采用FLAC对不同横坡坡度、围岩级别和侧覆土厚下的偏压隧道进行了开挖模拟,通过对隧道开挖变形特征及各关键点位移的分析,指出隧道在侧覆土厚大于20 m后基本不受偏压的影响,在侧覆土厚小于15 m时则需要在开挖前进行预加固措施。基于此,对不同工况下隧道进行的预加固措施的模拟分析,结果表明:V级围岩条件下,侧覆土小于7 m时主要需要解决的是浅埋侧反压能力不够的问题,而大于7 m后需要解决的则是深埋侧压力过大的问题,并在实际工程中得到验证。研究结论可为类似工程的设计和施工提供参考。

On the basis of considering all the influencing factors of unsymmetrical loaded tunnels, excavation of unsymmetrical loaded tunnels under different conditions of transversal gradient, surrounding rock grades and thickness of side covering soil were simulated by using FLAC. Then, the deformation behavior and key points＇ displacements of tunnel excavation were analysed. It is pointed out that the affect of unsymmetrical loading is no longer remarkable when the thickness of side covering soil is larger than 20 m, and pre- reinforcement is needed before excavation when the thickness of side covering soil is less than 15 m. Based on this, the pre-reinforcements of tunnel under different conditions were simulated. The results show that under the condition of surrounding rocks of grade V, the main problem is the insufficient counter pressure of shallow buried side when the thickness of side covering soil is less than 7 m, while the overpressure of deep buried side needed to be solved when the thickness is larger than 7 m. The resuhs have been verified in practice. The conclusion can be a reference for design and construction of similar engineering projects.