中文摘要：

相向施工的软弱围岩隧道临近贯通时，两开挖面的扰动区将会叠加，围岩应力及变形异常复杂，存在掌子面大变形和失稳问题。结合狮子垄隧道，采用数值手段分别对单向、相向施工时的隧道围岩应力与位移场进行研究，分析临近贯通时围岩的稳定性。结果表明，相向施工时，随着掌子面前方土体长度的减小，围岩塑性区明显增大，变形加剧，拱效应逐渐减弱，稳定性大大降低；两开挖面间存在极限距离，当2个掌子面距离小于该值时，围岩大范围临近塑性破坏，必须采取有效应对措施，方可保证隧道施工安全。在对掌子面加固、提高初支强度等措施效果分析的基础上，采用竹锚管注浆对狮子垄隧道贯通段掌子面进行加固，并提高初支强度，保证了该软弱围岩大断面隧道顺利安全贯通。

英文摘要：

When two excavation faces-of soft surrounding rock tunnel approach, large deformation and instability problem will appear on them because the disturbance area of excavation surface will be superimposed, and surrounding rock stress and deformation becoming extraordinarily complex. Combined with the study of surrounding rock stress and displacement caused by unidirectional and opposite excavation in Shizilong tunnel, the stability of tunnel face when two excavation faces is approaching is analyzed by numerical analysis. It is shown that （1） with the reduction in the length of the front of face soil during opposite construction, the plastic zone significantly increased, the deformation intensified, arching effect gradually weakened, and stability is greatly reduced; （2） there is a limited distance between two faces in the opposite excavation tunnel, when the two working tunnel face distance is less than the limited distance, a wide range of surrounding rock approach the plastic failure, only effective countermeasures been taken can guarantee the safety of the tunnel construction. After analyzing the effect of taking the measures such as tunnel face reinforcement and initial supporting strength improvement, when two excavation faces of Shizilong Tunnel is approaching, bamboo anchor pipe grouting is adopted to reinforce tunnel face with the initial supporting strength improved as well, which ensures the tunnel excavation is smooth and safe.