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Structural Monitoring of the Višnjica Tunnel PDF Print E-mail

tex_visnjica_02Client:
Belgrade Land Development Public Agency
Project Team:
Anica Jovičić, B.S.C.E.; Maja Pavić, B.S.CE
Consultant:
Milan Tričković, M.S.C.E.

The Višnjica Tunnel is the final segment of the main interceptor sewer of the Belgrade Sewerage System. The function of this interceptor sewer is to collect and evacuate sewage and a portion of stormwater from the city’s central drainage area. It originates at a pumping station near the Sava/Danube confluence and ends at a wastewater treatment plant in the Veliko Selo suburb.

 


Equipment for structural monitoring has been procured and monitoring is being conducted according to detailed design documents titled: Usce - Veliko Selo Interceptor Sewer Section from km 5+867 to km 12+639, Jaroslav Černi Institute, Belgrade, February 2008.

To monitor the tunnel during construction and subsequently during operation, the monitoring program requires convergence measurements at 23 monitoring stations and other types of measurements at fewer stations.

To date, the following electrical instruments have been incorporated into the tunnel’s concrete lining:

 

  • 12 extensometers, to monitor concrete strain in a plane perpendicular to the tunnel axis, tangential to the segment curve, tex_visnjica_01
  • 4 load cells at concrete/rock interfaces,
  • 4 load cells at concrete segment interfaces,
  • 4 uniaxial strain gauges, to monitor displacement of concrete segment couplings (allowing for measurements in the tangential direction, perpendicular to the coupling in a cross-sectional plane)


 The following additional monitoring equipment is used:

  • An instrument that measures convergence via benchmarks embedded in the tunnel lining, and
  • Load cells installed within the shield of the tunnel boring machine (TBM).

tex_visnjica_03Based on structural monitoring data compiled to date, the lining of the Višnjica Tunnel is stable and has not exhibited any indicators of a potential change in geometry. Forces acting on the tunnel lining and between individual segments, and lining strain levels, are below maximum design values. Additionally, forces acting on the TBM shield are within the expected range.

tex_visnjica_05

Concrete strain, closer to the outer surface of the tunnel lining

 
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