Hard Rock Tunnel Boring at the Follo Line Project
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The following report is the result of a field study carried out by the author at the Follo Line Project in Oslo. The overall purpose of the thesis was to collect as much TBM field data as possible during the available timeframe. In addition, the author has addressed a number of pre-defined research objectives which were linked to the NTNU prediction model, the use of optical televiewing, and the assessment of machine performance. In order to fulfil the objectives in question the following work was carried out: Collecting and processing TBM machine data from the on-board data-logging system. Acquiring handwritten shift logs and quantifying the information included in these. Collecting data regarding rock mass fracturing obtained on the basis of optical televiewing. Compiling geological and machine data in order carry out a comparison between predicted net penetration rate using the NTNU model, and the actual net penetration rate obtained from the processed machine data. Performing penetration testing, RPM testing, and drag testing.Among the results of the work carried out, are a presentation and assessment of machine performance with respect to the utilisation, operational parameters, and the duration of downtimes for the various activities carried out during excavation. The utilisation was found to be relatively good for the timeframe considered, but it is believed that it is somewhat overestimated. The research has also given an insight to how optical televiewing at the Follo Line Is used to back-map the rock mass fracturing based on the NTNU methodology. OTV seems to be an effective utility to be used for the back-mapping of geology in tunnels where the possibility to carry out visual interpretation of the open rock surface is limited, such as the case for concrete lined tunnels. The resulting rock mass fracturing factors (ks-tot) from the OTV were evaluated and it was found that they are subject to a number of potential uncertainties which seemingly have a significant influence on the ks-tot values obtained. It was concluded that it is necessary to investigate the usage of OTV further, in order to assess its accuracy and reliability in geological back-mapping. A large part of the work carried out in conjunction with this report, was the development of a new Excel based application to allow digitalisation of handwritten shift logs. The tool has first and foremost been used to acquire the needed information from the shift logs, but it has been designed with the intention to serve as a practical tool to be used for follow up work in future TBM projects. The machine testing conducted was limited to one round of testing and the results were found to be inconclusive for the RPM and drag tests.