Phyllite Tunnel Monitoring Technology And Application

As complex topography conditions of the west part of China, the construction of railway and highway will inevitably lead to the appearance of dangerous and complex tunnels, phyllite tunnel is a typical one of them. The strength of phyllite is high when it’s dry and will be drastically reduced when met with water. Therefore, large deformation, such as distortion of steel arch, crack of preliminary support, are particularly easy to occur in this stratum. In this paper, through the monitoring and measurement of construction and operation period of Du Jiashan highway tunnel, the following results and obtained:(1) It was found form the regular monitoring and measurement in tunnel’s construction process that, the convergence is generally large and the time is long to reach the steady state.(2) The monitoring and measurement scheme, monitoring results and controlling measures of some typical cross-sections for the tunnel under special conditions were studied The results show that, for large deformation section, targeted monitoring and measurement scheme can provide a strong basis for selecting appropriate and effective measures.(3) The monitoring data acquired form the long-term section shows that axial force and moment of Du Jiashan tunnel’s secondary lining are large. Their safety factors are low although the values can basically meet the specification requirements. So the risk of secondary lining is large. It’s also found that sericite phyllite has properties of weak and broken, low compressive strength, low cohesion, poor self-supporting and creep.