Evaluation of boring machine performance with special reference to geomechanical characteristics

The duration of tunneling projects mostly depends on the performance of boring machines. The performance of boring machines is a function of advance rate, which depends on the machine characterizations and geomechanical properties of rock mass. There were various theoretical and empirical models for estimating the advance rate. In this paper, after determining the geomechanical properties of rock mass encountered in the Isfahan metro tunnel, the performance of the roadheader and tunnel boring machine (TBM) were then evaluated using various models. The calculation results show that the average instantaneous cutting rate of the roadheader in sandstone and shale are 42.8 and 74.5 m³/h respectively. However the actual values in practice are 34.2 and 51.3 mm³/h. The operational cutting rate of the roadheader in sandstone and shale are 8.2 and 9.7 mm³/h respectively, but the actual values are 6.5 and 6.7 mm³/h. The penetration rate of the TBM in shale is predicted to be 50-60 mm/round.