浅埋软弱围岩隧道快速进洞方法及稳定性控制技术研究

Fast Entrance Excavation Method and Stability Control Techniques for a Shallow Tunnel with Uneven Rock Pressure and a Weak Rock Mass

浅埋软弱围岩隧道一般采取CD法、CRD法和侧壁导坑法进洞,这些常规进洞方法需设置或拆除大量临时支撑,在一定程度上影响了整座隧道的工程进度。文章以某高速公路隧道为依托,建立了在超前大管棚和小导管联合预支护条件下采用CD法、CRD法、双侧壁导坑法和三台阶七步法进洞的三维数值计算模型,对比分析了不同开挖方法控制围岩变形和支护受力的优劣,提出了"地表注浆+扩大拱脚+拱架Z型连接+拱脚槽钢纵梁"稳定性控制措施下的三台阶七步法快速进洞方案。数值计算和现场实测结果表明:该进洞方案更有利于发挥支护结构的棚架效应,可有效控制地层变位,减小支护应力,在保障安全进洞的同时,加快了施工的进度,可为类似工程提供参考和借鉴。

The excavation methods of CD, CRD and side heading are adopted to construct a shallow-buried tunnel portal in a weak rock mass with uneven rock pressure; a large number of temporary supports need to be set or re- moved, so the whole project schedule of the tunnel is affected. Based on a highway tunnel, the advantages and disad- vantages of rock mass deformation control and force on the support by different excavation methods （CD, CRD, side heading and three-bench-seven-step） were compared through a 3D numerical analysis with the condition of a com- bined support of a large advance pipe roof and small conduits. A fast three-bench and seven-step excavation scheme was proposed based on the factors of surface grouting, an expanding arch spring, a steel arch with a Z-type connection and longitudinal stability control at the arch spring. The numerical calculation and field measurements show that the pipe-roof effect of the steel arch support will be in full swing with this proposed entrance scheme, while strata displacement can be well controlled, support stress is reduced, and the construction progress goes faster.