Factors influencing performance of hard rock tunnel boring machines

Intact rock properties together with rock mass characteristics should be well investigated for selection of proper tunnel boring machine (TBM) for tunneling in various ground conditions. This is due to the significant impact of rock mass characteristics on machine performance. TBMs are site specific and designed for optimal performance in given ground conditions. When selected and put to work at a specific site, TBM parameters including thrust and power are the controlling factors for excavation rate. These two parameters along with rock properties and rock mass characteristics converge to define the operating point of a machine. To investigate the factors influence on TBM performance in rock mass, a database including two tunnel projects, the Queens Water Tunnel in the City of New York, USA and the Second Manapouri Tailrace Tunnel in New Zealand, have been compiled and studied. The relationship between the penetration rate, rock mass properties, and thrust and power consumption of the machine was examined. The obtained relationships together with the Colorado School of Mines TBM performance prediction model are discussed herein. © 2010 Taylor & Francis Group, London