ABSTRACT
The Musaimeer pump station and outfall project located in Doha (Qatar) was required to construct a long outfall tunnel using an Earth Pressure Balance (EPB) Tunnel Boring Machine (TBM) with a segmental lining. This tunnel had only one access point located at the launch shaft and was driven directly out from the shoreline, and connecting to a diffuser bed located 10.2 km offshore. The TBM cutter head was designed and equipped with both soft ground scrappers and hard ground cutter discs (Single, Twin and Double). The performance of any TBM can be influenced by many individual factors or combination of factors; perhaps the most significant of these factors is the performance of the cutting tools on the cutterhead. This paper will detail the two different specifications of hard ground cutters used and their individual performance and the impact of tribocorrosion on each type of cutter. The project had to carry out cutterhead interventions at full hydrostatic pressure (3.5 Bar) due to the extensive fractures in the seabed strata. The experience gained will be explained and the result was the changing of only 105 hard ground cutters during two years of tunnelling.
