Hard rock tunnel boring: Prognosis and costs

Abstract This paper is drawn from four project reports, dealing with: (1) hard rock tunnel boring; (2) drill-and-blast tunnelling—prognosis; (3) drill-and-blast tunnelling—costs; and (4) a drillability and drilling rate index catalogue. The project reports are based on jobsite follow-up work of both bored and blasted tunnels. This paper summarizes some developments in TBM and cutter design, factors influencing the boring process and factors that affecting tunnelling costs, e.g. the increased productivity possible with TBMs.