大断面软岩隧道施工监测分析与应用

为保证隧道施工期间围岩稳定和支护结构体系安全，本文结合超前地质预报与洞内、外地质观察，通过对某大断面软弱围岩公路隧道进行施工监控量测，分析处理地表下沉、拱顶下沉及周边收敛监测数据，研究其分布特征和变化规律。研究结果表明:该隧道施工工法和支护参数设计合理，围岩变形大都呈现“急剧增大—增速放缓—趋于稳定”趋势。当掌子面通过地表下沉监测断面10倍B时(B为隧道开挖宽度)，地表下沉趋近最终稳定值。当掌子面通过洞内监测断面3倍B时，拱顶下沉和周边收敛变化量可达最终值的80%左右；6倍B时，变化基本趋于稳定，且上台阶收敛变化量明显大于下台阶。当后行左洞与先行右洞掌子面之间的间距大于5倍B时，能有效减小后行洞施工对先行洞的影响。本文研究结果可为类似条件下隧道工程的设计、施工和监测等提供参考。

Monitoring Analysis and Application of Large Section Soft Rock Tunnel Construction

In order to ensure the stability of surrounding rock and the safety of supporting structure system and during tunnel construction, this paper combined with the advanced geological prediction and the hole inside and outside geological observation, By monitoring and measuring the construction of a large-section soft surrounding rock highway tunnel, the data of surface subsidence, vault subsidence and convergence around the tunnel were analyzed and processed, and its distribution characteristics and variation rules were studied. The research results show that the construction method and the supporting parameter design of this tunnel are reasonable and the deformation of surrounding rock has the trend of "increase sharply→slowly→steadily" in most cases. In addition, the surface subsidence eventually approaches the steady-state value. When the tunnel face passes through the surface subsidence monitoring section 10 times B(B for the tunnel excavation width). When the tunnel face passes through the inner monitoring section 3 times B, the vault settlement and the peripheral convergence can reach about 80% of the stable value; when 6 times B, the change tends to be stable. And the peripheral convergence variation of the upper step is obviously greater than the lower step. When the distance between the first hole right and the following hole left of tunnel face is more than 5 times B, their influence can be effectively reduced. This study can provide some useful reference for the design, construction and monitoring of tunnel engineering under similar conditions.