富水软弱围岩小净距隧道掌子面稳定性及超前管棚支护技术研究

Research on stability of small clear distance tunnel face and advanced pipe shed support technology in water-rich and weak surrounding rock

以义东高速公路防军隧道为例,通过理论分析与数值模拟相结合,研究了富水软弱围岩小净距隧道的掌子面稳定性与超前管棚支护技术。首先,基于管棚Winkler地基模型分析了掌子面稳定性安全系数,并采用Midas GTS NX有限元软件建立隧道模型;然后,分别分析了有、无超前管棚支护两种方案下的管棚弯矩、隧道围岩位移、衬砌应力以及特征断面掌子面稳定性的变化规律;最后,结合现场实际情况提出了富水软弱围岩隧道超前管棚的施工控制技术,并对其施工效果进行了监测。结果表明:采用超前支护与注浆加固后,可以减小裂隙水对围岩的侵蚀,提高围岩稳定性;施作超前管棚支护不仅能够改善掌子面的受力情况,使其安全系数增大了54.7%,且可减小隧道开挖时的拱顶沉降变形和有效控制掌子面塑性区发展,其中掌子面的挤出变形减小了约23%。

Taking the Fangjun Tunnel of Yiwu-Dongyang Expressway as an example,through the combination of theoretical analysis and numerical simulation,the stability of the tunnel face and the advanced pipe shed support technology of the small spacing tunnel in water-rich and weak surrounding rock are studied.Firstly,based on the Winkler foundation model of the pipe shed,the stability safety factor of the tunnel face is analyzed,and the tunnel model is established by the Midas GTS NX finite element software.Then,the bending moment of the pipe shed,the displacement of the surrounding rock of the tunnel,the lining stress and the stability of the tunnel face of the characteristic section under the two schemes of the pipe shed support with or without the advanced pipe shed are analyzed.The results show that the erosion effect of fissure water on surrounding rock can be reduced and the stability of surrounding rock can be improved by using advanced support and grouting reinforcement.The application of advanced pipe shed support can not only improve the stress of the tunnel face,but also increase the safety factor by 54.7%.It can also reduce the settlement deformation of the vault during tunnel excavation and effectively control the development of the plastic zone of the tunnel face.The extrusion deformation of the tunnel face is reduced by about 23%.