软弱围岩大跨度公路隧道施工方案研究

Study on Construction Schemes of Large-span Highway Tunnels in Weak Surrounding Rock

某公路隧道最大断面宽度为20.25 m,属于大跨度公路隧道。隧道洞身段围岩主要为IV级、V级砾岩、砂岩,具有岩质极软、岩体极破碎、自稳定能力差的特点。在施工扰动下,易发生软弱围岩自承能力丧失,引起塌方事故的发生。为确保该隧道的施工安全,根据该隧道的地质情况,选用中隔壁法和交叉中隔壁法为备选施工方案,对软弱围岩地区大跨度公路隧道的合理施工工法开展研究。研究表明采用中隔壁法施工时所产生的拱顶沉降、支护结构应力及地表沉降均为最小。中隔壁法可有效地控制大跨度公路隧道开挖工程中软弱围岩的稳定性。该研究成果可为类似工程提供有益参考。

The maximum section width of a highway tunnel is 20.25 m, and belongs to the large-span highway tunnel. The surrounding rocks at the section of the tunnel are the sandstones and conglomerates of Grade IV and Grade V with the characteristics of extreme soft rock, easily broken rock mass and poorself-stabilizing ability. The construction disturbance will easily cause the self-bearing capacity loss of weak surrounding rock and the landslide accidents. In order to ensure the construction safety of this tunnel, and based on the geological condition of this tunnel, the center diaphragm(CD) method and the center cross diagram(CRD) method are applied as the alternative construction scheme to study the reasonable construction method of large-span highway tunnel in weak surrounding rock zone. The study results show that the vault settlement, supporting structure stress and surface settlement caused by the CD method construction are the minimum. Therefore, the CD method can efficiently control the stability of weak surrounding rock in the excavation process of large-span highway tunnel. This study result can be referred for the similar projects.