Measurements of Cutter Forces for a TBM Machine in Äspö Underground Excavation

ABSTRACT: A vertical TBM machine was used to drill 1.8 m-diameter boreholes for nuclear waste depository in Äspö underground tunnel, Sweden. The three forces-normal force, tangential force, and side force-on both one front button cutter and one gauge button cutter were measured during the field excavation. Three-group strain gauges were installed on the shafts of the two cutters for recording their voltage variation during excavation. Because the three forces are always coupled together, the laboratory calibration considered such a coupling problem. According to the field measurements, we obtained the actual normal force, tangential force, and side force. The results indicate that the maximum normal force, tangential force, and side force of the front cutter in 7-minute excavation can reach 700 kN, 120 kN, and 175 kN, respectively. However, the maxi-mum normal force, tangential force, and side force of the gauge cutter in the same period are only 150 kN, 80 kN, and 20 kN, respectively. Then each force-time curve was analysed by using spectrum analysis.