Author(s):
1. Marpol Koço, Ministry of Energy and Industry, Albania
2. Ferdinand Kullollli, Devoll Hydropower Project.Statkraft, Albania, Albania

Abstract:
Tunnel Convergence monitoring is a basic tool for understanding and documentation of rock mass behaviour, during excavation phase. This paper gives a brief description of convergence monitoring process of two similar road tunnel projects located in two different types of rock.Detection of anomalies in a short period, moreover the displacement of preliminary support lining is partially a matter of safety condition and provides clear overview of the rock mass behaviour givingthe opportunity of taking immediate actions toward stabilization. In order to use the obtained data into mathematical models for tunnel design during excavation phases,a plot of absolute displacement with an accuracy of -/+1mm is provided An optical system used for monitoring displacement in tunnelling is based on the use of survey equipment as Total Station and installation of convergence stations, composed by reflective targets on the preliminary support. Assuming that methods used for tunnelling is practically the same, it has been focused on comparing data’s between most problematic zones and designing additional rock support based on convergence stations results. Specific cases are being presented, where the optical method needs to be revised on regard of surrounding environment conditions.Working with the same revised method in both cases presented, after performingan error source analysis, it is not observed big deviation from the accuracy expected. In exchange for achievement of acertain accuracy, a secure path for detecting the real tunnel displacement between two different rock mass fault zones is provided.

Key words:
Tunnels,Convergence,Displacement,Monitoring,NATM

Thematic field:
The logistics processes and environmental effects

Date of abstract submission:
15.06.2017.

Conference:
7th Balkan Mining Congress